Saturday, May 31, 2008

Turf - June is the Start of Brown Patch Season in Tall Fescue Turf

June will bring us hot and humid weather. In turf this will mean brown patch disease starting to show up. The following is information on this disease from NC State University.

Brown patch is the most common and damaging disease of tall fescue in Delaware. The symptoms of brown patch are roughly circular patches that are brown, tan, or yellow in color, ranging from 6 inches to several feet in diameter. The affected leaves typically remain upright, and lesions are evident on the leaves which are tan in color, have a dark brown border, and are irregular in shape. When the leaves are wet or humidity is high, small amounts of gray cottony growth, called mycelium, may be seen growing amongst affected leaves in the turf canopy.

Brown patch is most severe during extended periods of hot, humid weather. The disease can begin to develop when night temperatures exceed 60°F, but is most severe when low and high temperatures are above 70°F and 90°F, respectively. Brown patch also requires at least 10 to 12 hours of continuous leaf wetness in order to develop. Poor soil drainage, lack of air movement, shade, cloudy weather, heavy dew, over-watering, and watering in late afternoon favor prolonged leaf wetness and increased disease severity. Brown patch is particularly severe in turf that has been fertilized with excessive nitrogen. Inadequate levels of phosphorus and potassium have also been shown to contribute to injury from this disease.

Varieties of tall fescue vary widely in their susceptibility to brown patch. Selection of a tall fescue variety with a high level of brown patch resistance is a critical first step in any management program. Current lists of varieties with good brown patch resistance that perform well in Delaware can be found at the National Turfgrass Evaluation Program (

High levels of available nitrogen favor the spread of brown patch. Nitrogen induces tall fescue to produce soft, lush leaf tissue that is easily infected by the brown patch pathogen. Excessive foliar growth also results in a dense canopy that holds moisture and humidity for extended periods of time.

In general, tall fescue should not be fertilized with nitrogen in late spring or summer so as to discourage brown patch development. Following this type of program will result in yellowing and thinning of tall fescue during the summer as nitrogen is depleted from the soil. Turf in this condition is very resistant to brown patch, but may not be acceptable from an aesthetic standpoint. If fungicides are used to protect tall fescue from brown patch, then application of small amounts of slow-release nitrogen (≤ 0.25 lb N/1000 ft2/month) during the summer can help improve the quality of tall fescue turf. This practice, however, will encourage the development of other diseases, such as gray leaf spot and Pythium blight. Tall fescue that is fertilized during the summer should be monitored frequently for these diseases so that they may be controlled before widespread damage occurs.

Avoiding prolonged periods of leaf wetness will drastically reduce the severity of brown patch. Leaf wetness can originate from either irrigation or dew. To minimize leaf wetness, do not irrigate the turf on a daily basis. Instead, water deep and infrequent, every 3 to 4 days to a depth of 6 to 8 inches. The timing of irrigation is also critical; it is best to irrigate early in the morning, just before sunrise. This removes large droplets of dew and guttation water from the leaves and speeds drying of the foliage after sunrise. Avoid water­ing after sunrise or in the late afternoon/evening, as this will increase the duration of leaf wetness. For intensely managed athletic fields, daily removal of morning dew can help to reduce leaf wetness duration and minimize brown patch development. This can be accom­plished by mowing, dragging a hose or rope over the turf, or running the irrigation system for a short time.

Brown patch is particularly severe in soils that are wet and compacted. Providing adequate surface and subsurface drainage, and minimizing compaction through regular aerification, will help to minimize the development of this disease.

Fungicides are effective for brown patch control, and can be applied on a preventative or curative basis. Fungicides vary widely in residual control, or the number of days of brown patch control after application. Fungicides containing the active ingredients azoxystrobin (Heritage 50WG, 0.2 oz/1000 ft2), pyraclostrobin (Insignia, 0.7 oz/1000 ft2) or flutolanil (Prostar 70WP, 2.25 oz/1000 ft2; Systar 80WDG, 3 oz/1000 ft2) consistently provide 28 days of brown patch control, even under severe conditions. For homeowner applications, products containing the thiophanate-methyl are sold under various brand names at garden stores and provide good brown patch control, but these products must be re-applied every 14 days.

Curative fungicide applications for brown patch may not be effective during periods of hot weather because tall fescue does not grow well during these conditions and will recover from brown patch injury very slowly. For this reason, a preventive fungicide program should be considered on tall fescue when conditions are favorable for disease development.

Information from "Managing Diseases of Tall Fescue" Turfgrass Disease Information Note 6 (TURF-006) by Lane P. Tredway, Extension Turfgrass Pathologist, North Carolina State University. Go to the following website for the full fact sheet:

Landscape and Nursery - Ambrosia Beetles

The ambrosia beetle, Xylosanrus germanus, is showing up in a wider range of plant material. Be on the watch for this pest as it can be very damaging, especially in nurseries. The following is a report from the University of Maryland.

University of Maryland Extension personnel have found Ambrosia beetles in London plane, river birch, zelkova, dogwood, sugar maple, sweet bay magnolia, Styrax and now golden rain trees. We Be sure you examine the trees in your nursery for the characteristic pencil-like thread of wood and frass projecting from your trees.

Top picture ambrosia beetle, bottom picture, characteristic damage.

Control: The beetles of the first generation are in the larval stage at this time. You can apply Onyx or Astro now to try and control the second generation that will come out at the end of June. There will already be damage from the first generation of beetles.

Information from the May 30, 2008 edition of the TPM/IPM Weekly Report for Arborists, Landscape Managers & Nursery Managers from the University of Maryland Cooperative Extension.

Friday, May 30, 2008

Landscape and Nursery - Scales to Watch For

The following is information on some scale pests you should watch for and apply control measures in the next few weeks.

Two species of Lecanium scales are problematic in our landscapes and the next few weeks offer good management opportunities. Fletcher scale (Parthenolecanium fletcheri) affects a wide variety of coniferous plants such as Taxus, arborvitae, junipers, and even Taxodium spp.. European fruit lecanium (Parthenolecanium corni) affects a broad range of broadleaved woody plants such as redbud, hawthorn, dogwood, and oak.

These soft scales appear like little brown lumps grouped along tree branches as adults. They feed in the phloem (on plant sap). Honeydew rain (clear sticky substance that is scale excrement) from the developing nymphs and adults of both species was noticeable in early May. A black fungus called sooty mold often grows on the honeydew.

Lecanium scales have one generation per year. Crawlers will start to appear in early June and will migrate to the undersides of leaves/needles and spend the summer months there then migrate back to the branches to spend the fall and winter. They will resume growth, mate, and lay eggs the following spring.

The settled crawler stage is the best time to control lecanium scales. Many insecticidal products are registered for this purpose but horticultural oils work quite well. Occasionally, a re-application is needed about 3 weeks after the initial application to ensure that all crawlers have emerged. Many naturally occurring parasites and predators often control lecanium scales,
but parasites have been less active recently on a regional level. Still, many predators such as lady beetles feed on them. Insecticides sprayed later provide only limited effectiveness against nymphs and soil systemic insecticide applications must be properly timed.

Information from Casey Sclar, IPM Coordinator, Longwood Gardens

Turf - Using Spent Mushroom Soil as an Ammendment

We ge a lot of questions on the use of mushroom soil on turf. The following are guidelines for selecting a mushroom soil from Penn State University.

Selecting a Spent Mushroom Soil (SMS) product - some guidelines to follow

Although many of the ingredients that go into SMS products are similar, not all products are alike. Quality of SMS can vary depending on the ingredients, how it is produced, and how it is treated after it comes out of the mushroom production houses. Because of potential quality differences among products, it is important to have some basis for determining suitability for use on turf. Ideally, the product you intend to use has been field tested and used successfully by other turf managers. Using a SMS product with a proven track record can take some of the guess work out of the selection process provided that it is consistent from batch to batch.
Whether you are using a field-tested SMS or one that has never been used on turf, be sure to obtain a sample of the product prior to use and examine it for undesirable objects and peculiar or offensive odors. If the producer does not have an analysis of chemical and physical properties, submit a representative sample to a laboratory that will conduct appropriate tests and provide recommendations that you can understand. Penn State's Agricultural Analytical Services Laboratory offers a compost testing service with several options for analysis of SMS products. Information on the compost testing program and other soil testing programs can be accessed at

Some basic guidelines for evaluating the suitability of SMS products for use on turf follows.
General appearance: The appearance of fresh SMS is similar to peat, with a light brown color and a light, fibrous texture. Weathered SMS products should resemble dark topsoil and have a loose, crumbly structure. All SMS products to be used on turf should be free of large stones, plastic, and other objectionable objects.

Particle size: The size of SMS particles can vary depending on how it is produced. For use in surface applications on athletic fields, lawns, or golf course fairways, the SMS should pass through a 1/2 inch screen (or be of similar size). Composts with slightly larger particles can be used as soil amendments if thoroughly tilled into the soil prior to seeding or sodding.
Odor: A good quality SMS product should have an 'earthy' aroma. It should not emit peculiar or offensive odors such as those associated sulfur or rotten eggs. Also, it should not emit a strong ammonia odor. Peculiar odors may be an indication that the product is not mature (not fully composted). Immature SMS may have adverse effects on turf and should not be used.

Weed seeds: If the SMS product has been properly composted and stored, weed seed contamination will not be a problem. On rare occasions, SMS products are stored for long periods and neglected. In such cases, weed plants can begin to grow in the piles. If these weeds are not controlled immediately they can deposit seeds in the product.

Although a few weed seeds do not necessarily preclude the use of a SMS product as a soil amendment for turf, products containing large amounts of weed seeds are unacceptable. If possible, inspect the production site to make sure that weeds are not growing in and around the SMS piles.

Moisture content: The moisture content of a SMS product is important where uniform application and good mixing with soil is desired. Products with moisture contents between 30 and 50% are usually ideal for handling, surface applications, and soil incorporation. Wet products (greater than 60% moisture content) tend to form clumps and do not spread evenly when applied to turf surfaces. Tilling wet material into soil may result in poor mixing with soil and uneven turf establishment. Wet SMS is heavy and difficult to handle.

A quick field test that you can use to determine suitable water content of SMS is to squeeze the product in the palm of your hand and watch for water oozing from the product. If water drips from the SMS upon squeezing, then the product may be too wet, and further drying should improve product handling. If the SMS remains together when you release your grip and no water drips from the product, it probably has suitable water content for spreading and mixing with soil.

Organic matter and ash content: When using SMS as an organic matter supplement, keep in mind that not all of the product is organic matter. Spent mushroom substrate products typically contain between 40 and 60% organic matter on a dry weight basis. Organic matter content can be determined by a lab test. The most common procedure employed by laboratories, "loss on ignition", considers everything that is combustible as organic matter.

Some test labs report a value called 'ash content'. Ash is the mineral matter that remains after the SMS sample has been subjected to extremely high temperatures in a furnace. Assuming that everything burned-off in the furnace is organic matter, the percentage of ash in the sample can be subtracted from 100 to provide an estimate of percent organic matter. For example, an ash content of 40% indicates that there is an estimated 60% organic matter in the sample.
Carbon to nitrogen ratio: The amount of carbon (C) relative to the amount of nitrogen (N) in a SMS product is an important indicator of nitrogen availability. The carbon to nitrogen (C:N) ratio of a product should be 30:1 or below. If above 35:1, soil microorganisms can immobilize nitrogen, making it unavailable to the turf. Most SMS products have C:N ratios well below 30:1.

Nutrients: When compared with fertilizers, SMS products generally contain low amounts of plant nutrients. Whereas a small amount of quick-release nitrogen (ammonium) is present in SMS, most nitrogen is in the organic form and is slowly available to turf. Test results of SMS products typically indicate 1.5 to 3% total nitrogen on a dry weight basis. Other nutrients found in SMS include phosphorus (0.5 to 2.0 %, reported as P2O5), potassium (1.0 to 3.0%, reported as K2O), calcium (3 to 6%), and magnesium (0.4 to 1.0%).

Typically, significant amounts of SMS must be applied to supply all or most of the turf's nutrient requirements. In some cases, this can be achieved for short durations (8 to 10 weeks) with surface applications of ¼ to ½ inch of SMS, aerated into the soil surface. In many cases, a 1 or 2 inch layer of SMS tilled 4 to 6 inches into soil can supply all of the nutrients necessary for turf growth and development for an entire year and possibly longer.

pH: The pH of most SMS products is between 6.0 and 8.0, a range favorable for turf root growth. On rare occasion, a product may fall outside of this range. The pH of organic amendments may be detrimental to turf when very high (greater than 8.5) or very low (less than 5.5). Extremes in pH may result in reduced availability of some plant nutrients and/or aluminum toxicity problems. Fortunately, most soils are buffered against rapid and drastic changes in pH and even organic amendments with extremes in pH may not alter the overall soil pH a great deal. To be on the safe side, however, try using products with a pH between 6.0 and 8.0.

Soluble salts: Soluble salts may be higher in SMS products than in other types of organic amendments. Whereas, excess soluble salts can cause turf injury, research conducted at Penn State shows that good quality SMS products do not contain salt levels high enough to damage turf. If you have questions regarding the soluble salt content of a particular SMS product and how safe it is to use on turf, send the product to a soil test lab that performs soluble salts analyses on composts.

Penn State's Agricultural Analytical Services Lab and other laboratories measure soluble salt content in SMS by saturating the sample with water, extracting the solution from the sample, and determining salt content by measuring the electrical conductivity of the solution. The higher the electrical conductivity of the solution, the higher is the salt content of the SMS. Soluble salt content is most often reported in units of electrical conductivity (mmhos/cm or dS/m).

From "USING SPENT MUSHROOM SUBSTRATE (MUSHROOM SOIL) AS A SOIL AMENDMENT TO IMPROVE TURF" Department of Crop and Soil Sciences - Cooperative Extension, Penn State University

Thursday, May 29, 2008

Turf - Apply Bermudagrass Control Measures Soon

Bermudagrass control in cool season turf can be a challenge. There are some herbicide tools available but you need to start early. First herbicide applications should go on now. The following are some recommendations.

Bermudagrass suppression has been achieved by applications of Acclaim extra (fexoxaprop-p-ethyl) applied at 0.46 fl. oz. per 1000 sq. ft. every 4-5 weeks (maximum of 6 applications) starting at bermudagrass first greenup in May. Acclaim extra mixed in combination with Prograss (ethofumisate) or Turflon Ester (triclopyr) has given better bermudagrass control (do not use Prograss on fine fescues) and fewer applications may be needed. Both Prograss and Turflon Ester both have some bermudagrass activity when used alone.

This program based on Acclaim Extra will be the best option for light to moderate infestations. For heavy infestations a complete renovation will be needed. Kill the bermudagrass with glyphosate applications (2 applications, 3 weeks apart) in mid summer and reseed around Labor Day.

Gordon Johnson, Extension Horticulture Agent, UD, Kent County

Nursery, Landscape, and Turf - Moisture and Diseases

Moist conditions favor disease development in landscape plants. The following is an article on the subject.

In Mid-May, there were days with persistent rain, mist, fog, and humid, overcast weather in many parts of Delaware. Wet weather increases disease pressure for most foliar fungal and bacterial diseases of plants in the garden and landscape. Many fungal pathogens require free moisture on the host plant surface for germination of their spores. The longer it is that leaves remain continuously wet, the better chance it is that fungal spores on the host will succeed in infecting the host plant. At average temperatures of 60-65 F, the apple scab fungus needs 9 consecutive hours of wet leaves for successful infection, the grape black rot fungus needs 8-9 hours, the rose black spot fungus needs 7 hours, shade tree anthracnose fungi need 6-12 hours, and the cedar-apple rust fungus needs only 3-4 hours. Following infection promoted by wet weather, disease symptoms typically appear on the plant a week or two later.

The two other components of the plant disease triangle, the susceptible host and the virulent pathogen are needed for a disease outbreak. For example, diseases such as apple scab, oak anthracnose, cedar-apple rust, and rose black spot are already present on susceptible host plants in many landscapes. These infections occurred during wet periods this past month. Depending on where susceptible plants are located, recent disease-favorable wetness periods have lasted anywhere from 9 hours in one day to 45 consecutive hours over two or three days. Thus, for the rest of this spring and even into summer, expect these infections to produce symptoms and more spores to continue the cycle of disease every time a prolonged wet period occurs.

Adapted from COMPLETING THE PLANT DISEASE TRIANGLE - DISEASE-FAVORABLE ENVIRONMENT By John Hartman in the May 19 edition of the Kentucky Pest News from the University of Kentucky, College of Agriculture.

Wednesday, May 28, 2008

Nursery and Landscape - Learn More About Phytophthora

Phytophthora diseases are a common problem in Delaware nurseries and landscapes. You can learn more about diseases caused by these organisms now with an on-line course from Oregon State University. The following is information on this training.

Phytophthora, a fungus-like organism, is a persistent threat to nursery crop production and landscape plantings in Delaware. Learning more about this plant pathogen and the diseases it causes would benefit anyone involved in the nursery or landscape trade. In addition, nursery growers are aware of the need to be alert for new diseases such as "sudden oak death" (also known as ramorum shoot and leaf blight on nursery stock) caused by Phytophthora ramorum. Growers who examine their plants carefully are, in effect, "first detectors" of new and exotic diseases in the nursery industry. Nursery producers and landscapers now can participate in a free online Phytophthora training program from Oregon State University. The goal of helping to minimize these diseases in the nursery setting; however, landscapers should alsto benefit. The training is free and consists of three 1 to 1.5 hour modules. There is an optional online exam that does have a fee of $100. If you pass the test, participants will receive a Certificate of Mastery on Phytophthora from Oregon State University Extended Campus. For more information on this training, please visit the OSU Phytophthora Online Course. A link is given below.

Nursery and Landscape - Biological Fungicides

There are a number of biological fungicides on the market. The following is information on these products and their effectiveness.

Biological fungicides tend to have negligible toxicity to humans, and no history of carcinogenic or developmental effects on test animals. Data on the effectiveness of the biologicals in landscape use is often limited, but the labels are helpfully broad, encouraging product use for suppression of many different pathogens. Some of the pathogens named on the label may have been suppressed in laboratory plate tests rather than in field trials; time will tell whether they are also effectively treated for under the less controlled conditions in the outdoor environment. Rather than thinking of biofungicides as cures for diseases, think of them as biological tools for treating plants preventively, decreasing the odds that a pathogen will successfully attack to cause disease. Biological controls are thus used as health insurance, not in response to the appearance of disease symptoms. They are very compatible with overall integrated pest management (IPM) philosophy—but one should not wait for a disease threshold to be reached before deploying a biofungicide. In many instances, the best use of a biological may be occasional treatments in alternation with reduced-risk chemicals.

One of the best known of the biologicals for disease control is Rhapsody AS, which contains Bacillus subtilis strain QST 713, a bacterium. This protectant material is even approved by OMRI for use in organic production, as well as for use in a broad range of sites including landscapes and golf courses, plus sod and ornamental production. Using a surfactant to improve coverage is recommended, and the higher labeled rates may be needed under significant disease pressure. Rhapsody may be applied as a spray or as a drench. As a spray, its forté is powdery mildew, but a measurable benefit from Rhapsody has also been seen against some bacterial leaf spots, Cercospora leaf spot, Botrytis blight and downy mildew. Only copper treatments offer similar versatility, with effectiveness against bacteria as well as fungi. As a soil drench, the Rhapsody label offers suppression of Fusarium, Pythium, Phytophthora and Rhizoctonia.

Actinovate SP, a biofungicide labeled for production and landscape use, has Streptomyces lydicus WYEC 108, an actinomycete, as its active ingredient. Drenches and foliar sprays may be made in the landscape as new plants are being transplanted, or to established plants. Treatments are of benefit only when made preventively. Actinovate’s original use was for soilborne diseases—the label lists problems caused by Pythium, Rhizoctonia, Phytophthora, Verticillium and Fusarium. Some suppression of powdery mildew, downy mildew, Botrytis, Alternaria, and Sclerotinia is also claimed for foliar applications. Studies on ornamental crops have thus far shown powdery mildew and Botrytis to be measurably reduced by Actinovate treatment. The Actinovate AG label, which relates to agricultural uses, includes a mention of Monilinia control, which suggests that the Actinovate SP may help to keep ornamental cherries free from brown rot. This biocontrol is effective at temperatures above 45ºF. A non-ionic spreader-sticker such as Latron B1956 should be added for the best results. For landscape use, treatment can be at transplant or to established plants. Ornamental bulbs may also be dusted or soaked in a suspension of Actinovate SP prior to planting, or drenched subsequently. The material may also be used for pre-plant treatment of bare-root trees.

Information from "Exploring alternatives for disease control on trees and shrubs" by Margery Daughtrey, Cornell University Department of Plant Pathology and Plant-Microbe Biology in the May 23 edition of the Michigan State University Landscape Alert Newsletter.

Tuesday, May 27, 2008

Greenhouse and Nursery - Use of Florel on Garden Mums

As garden mums start to arrive at greenhouses, growers may consider using Florel to replace hand or mechanical pinching. The following information from Rick Yates, Griffin Greenhouse and Nursery Supplies Inc. provides some good details on using Florel.

Florel can be used to replace mechanical pinching when applied as a thorough foliar spray at 500 PPM (1.6 oz./gal.). Typically this is done one week before you would hand pinch. Even though your cell pack mums are pinched when you receive them, they will benefit from an application of Florel applied as soon as possible after they arrive. While this initial spray to pinched cuttings does not increase branching, it does reduce premature budding by getting the plants under the influence of Florel as early as possible. Repeated at two week intervals, Florel helps to keep plants vegetative as well as providing more breaks per plant when compared to hand pinching.

Florel also reduces internode elongation, reducing or eliminating the need for other growth regulators later in the season. Labor savings are significant and greatly appreciated! Using more than 1 pinch and 2 Florel treatments (counting the one applied when you received the pinched cuttings) is not usually desirable. So many branches are produced that stem strength is reduced and the plants may pull apart at flowering.

Most growers report great results from one application upon arrival, and one more 14 days later. You can also time your crop with Florel, since it delays flowering. Make your last Florel application before July 1st to avoid delaying the natural season flower date. CAUTION: Highly alkaline water may need to be treated in order for Florel to be effective. When Florel is added to your spray tank it must be able to drop the pH of that solution to between 4.0 and 5.0 to work properly. Distilled or acidified water may be needed in some cases. Use an acidifier to adjust the pH of the spray water to between 5.5 and 6.0 before adding the Florel to allow the final solution to be in the correct range.

Sample Program (normal season flowering)

Pinched cuttings arrive about June 10th and are sprayed upon arrival with Florel @ 500 ppm

Two days later (allows for 48 hr REI for Florel) cuttings are potted into 8 x 5 or 9 x 6 mum pans.

Reapply Florel @ 500 ppm two weeks after the first treatment (~ June 24th)

Information from the Fact Sheet: "Garden Mums from Cell Packs" by Rick Yates, Griffin Greenhouse and Nursery Supplies, Inc.

Landscape and Nursery - Boxwood Spider Mite

The Boxwood Spider Mite, Eurytetranychus buxi, is a problem pest in Delaware. The following is information on this pest that is hatching now and its control.

Boxwood spider mites started hatching this week. They overwintered as eggs. The mites are small and clear to light yellow in color and you will need a hand lens to see them. As they mature they will be light yellow to yellowish-brown. They are on the undersides of the foliage. The feeding of the mites will cause stippling to the foliage and heavily infested leaves will turn yellow and drop.

Control: Japanese boxwood appears to be less susceptible, but we found boxwood mite on several cultivars of Japanese boxwoods growing in full sun in 2007. The common boxwood such as the English and European types tends to be very susceptible. Columnar forms of boxwood appear to be very susceptible. We have used the mite growth regulator Hexagon and obtained season long control if applied early in the season. Other materials that work well include Floramite, Akari, Avid, and horticultural oil (directed at the undersides of the foliage).

Reprinted from the May 23, 2008 edition of the TPM/IPM Weekly Report for Arborists,
Landscape Managers & Nursery Managers from the University of Maryland Cooperative Extension.

Monday, May 26, 2008

Landscape - Some Beneficial Beetles

Everyone is aware that lady beetles are beneficial as they are a great aphid predator. However, there are other beneficial beetles in the landscape. The following is an article on the subject.

Ground beetles (family Carabidae) are important predators that can be found in most gardens and home grounds. They may be the most numerous predatory insect around the home. They vary in size from less than ¼" to over 1½" long. Adult ground beetles run quickly when disturbed, but they rarely fly.

The adults of most ground beetles are dark brown or black, shiny, and somewhat flattened, with slender legs for running. A few are iridescent blue or green. They are commonly found under leaves or debris, in cracks in the soil, or running along the ground (but not often in bright sunlight). Some species also climb into trees, shrubs, and crop plants looking for prey. They may wander indoors at ground-level entry areas.

Adult ground beetles are fierce predators that chew up their prey with large, sharp mouthparts. Common prey include caterpillars, grubs and adults of other beetles, fly maggots and pupae, earthworms, and other small soil dwellers. They can consume their body weight in food daily.

Firefly larvae feed primarily on snails and slugs. Like the more familiar adults, they are mainly nocturnal in habit. They prefer moist habitats, such as under boards, decaying vegetation and beneath bark. Closely related glowworms (larvae and the adult female are luminescent) occur in more wooded areas and feed primarily on millipedes and soft-bodied insects under decaying tree bark.

Soldier beetles resemble fireflies – their larvae are predacious (as are fireflies), but compared to fireflies, adults and larvae are more active during the day. Acommonly are seen on flowers, and larvae prefer the "old field" habitat. Click beetles are another familiar adult beetle. The larvae of some click beetle speciefeed on insects in dark, secluded environments.

The family Staphylinidae, or rove beetles, with about 2,900 species, is the largest family of North American beetles. Most species are small and seldom seen. Although common, the group as a whole is not well studied. Some species are predaceous as in adults and larval stages; the larvae of other species are parasitoids and others are scavengers.

Adult rove beetles are generally less than ¾ inch long. They are recognized by their slender, usually black or brown bodies and shortened front wings (elytra) that may look like pads on the abdomen. When disturbed rove beetle adults have the distinctive behavior of curling the tip of the abdomen upwards. Adults are usually strong fliers despite the shortened forewings (hindwings are normal sized). The mobile larvae of nonparasitic rove beetles may be distinctly segmented.

Most rove beetles are found in association with soil or decaying organic matter. They may be seen under debris or rocks, in compost piles or crawling on plants. They are frequently found in soils when in home gardens. Adults will visit flowers to feed on pollen.

Predaceous rove beetles, depending on the species, feed on eggs and larvae of mites, insect eggs or small soil insects. Some feed on the eggs and maggots of flies. A few species found in vegetation feed on many types of small insects and mites.

Information from Dewey Caron, Extension Entomologist, UD.

Landscape and Nursery - Phos-Acid Fungicides

We have seen a proliferation of phos-acid fungicides in recent years. These are reduced risk products that have been very effective on certain diseases. The following is an article on the subject.

Another category of “safer” systemic materials are the phosphorous acids or phosphonates. The first of these was Aliette, fosetyl-Al, which was introduced decades ago. Now a large number of products including Avalon, Flanker, Phostrol, Alude, Fungi-Phite T&O, and K-Phite have been labeled in New York with the same mode of action as Aliette. These vary in their acidity, and in whether there is aluminum included in the formulation, but they all have similar modes of action. The phos acid materials offer some key uses: downy mildew control on roses, Pythium and Phytophthora management, as well as some suppression against certain bacterial diseases. Aluminum toxicity has been problematic with application of Aliette on some plants, such as azaleas. Precautions given on some of the phos acid labels indicate that they should not be applied to heat-stressed or drought-stressed plants, or within 14-20 days of a copper application. These materials should not be applied if the foliage will not dry promptly. Some of the phos acid products are not safe to tank-mix with spreader-stickers, or with flowable chlorothalonil or mancozeb products, so be careful to read the label of the particular material you are using.The phos acid materials may be used on ornamental and bedding plants in landscape, nursery and greenhouse. The ability of these materials to limit Phytophthora disease is unquestioned—this is their strongest suit. Results on other kinds of diseases will be variable. The leaf spot on English ivy caused by Xanthomonas campestris pv. Hederae is one of the bacterial diseases for which phos acids are labeled. Fire blight suppression is also listed for some ornamentals.

Reprinted from "Exploring alternatives for disease control on trees and shrubs" by Margery Daughtrey, Cornell University Department of Plant Pathology and Plant-Microbe Biology, in the May 23, 2008 edition of the Michigan State University Landscape Alert newsletter.

Sunday, May 25, 2008

Landscape - Cool Weather Favors Aphids; Look for Aphid Predators

Aphids are very common in spring on a large variety of plants because the weather favors them over their enemies like lady bug beetles, lacewings, and hover flies (Syrphid flies). This is more prenounced in a cool spring like we have been having. The following are images and information on the natural controls of aphids.

Aphids are found predominately on the undersides of leaves. Aphid feeding often causes leaves to curl under making it difficult for predators to reach them. Aphid populations explode quickly because they are all females giving live birth to females, which will soon be giving live birth to females. Insecticides may not be necessary if there are enough predators present. Look for the adult lady bug beetles and their larvae (they look like alligators), lacewing larvae (with long scissorlike mouthparts extending out of their heads) and hover flies (tiny sluglike larvae).

Green lacewing larve feeding on aphid. Photo by Whitney Cranshaw, Colorado State University,

Syrphid (Hover) fly larvae, a predator of aphids. Photo by Whitney Cranshaw, Colorado State University,

Lady beetle larvae, a predator of aphids. Photo by Frank Peairs, Colorado State University,

Turf - Cool Temperatures and Herbicide Activity

We have had an unusually cool May. Broadleaf herbicide activity can be affected by these cold temperatures. The following is an article on the subject.

As most of us know, optimum weed control with broadleaf weed herbicide mixtures is obtained when weeds are actively growing. Conditions that promote active growth are good soil moisture and moderate daytime/nighttime air temperatures. In general broadleaf weed herbicide mixtures work best when applied when daytime air temperatures range between 75 to 85 degrees and nighttime temperatures range between 55 to 65 degrees. April and May have brought us a prolonged early spring weather pattern with many days below 70 degrees and nights below 50 degrees. Due to these cool weather conditions herbicide activity has been very slow to develop.

This has been observed even with herbicide mixtures formulated as esters, which work better in cooler weather conditions. In addition, up until May 12 we experienced dry soil conditions, which may also detract from optimum broadleaf weed herbicide activity if applications were made prior to May 12 on sites that were not receiving supplemental irrigation. Due to these conditions expect the possibility of a significant number of broadleaf weed herbicide failures for applications made prior to May 12 regardless of the product. This possibility may be even greater for tougher to control broadleaf weeds such as oxalis, veronica, ground ivy, and mouseear chickweed. Keep a close watch on sites that have received broadleaf weed herbicide applications under these conditions. If re-treatment is necessary, wait for more moderate air temperatures and visible signs of active regrowth of the weeds before a second herbicide application.

Information adapted from an article by Dr. Steve Hart, Turf and Ornamental Weed Specialist, Rutgers University.

Saturday, May 24, 2008

Turf - Volatilization and Drift of 2,4-D and Dicamba

Many broadleaf control products in turf contain dicamba and/or 2,4-D. Sometimes, late spring and summer applications of these materials are used to control broadleaf weed escapes (those not controlled by spring treatments). Unfortunately, these material may volatilize and move from the site of application in hot weather. The following is an article on the subject.

Common sense is critical for spraying dicamba and 2,4-D. Both of these products are volatile and prone to move from the treated areas as vapors. Volatility can cause dicamba or 2,4-D to move up to a few miles. Spraying these postemergence broadleaf herbicides in large turf areas may require additional considerations because of the temperature. Furthermore, many of the home gardens and landscapes have been planted with vegetables, fruits, and annual plants and they are often very sensitive to these herbicides. It is not recommended to spray dicamba or 2,4-D when the temperature is expected to be 85 degrees or hotter; or spray late in the day when temperatures drop below 85. Many turf herbicide pre-mixes have dicamba and/or 2,4-D. Use lower drift formulations of these products when available. Amines and esters are the most common formulations of 2,4-D. The esters are the most active and can be used at the lower rates and for brush control. Since vapour drift is a potential problem with the ester formulations, only the amines should be used on lawns, or near gardens. Granular products are somewhat safer but still can volatilize under certain conditions.

Information from Mark VanGessel, Extension Weed Specialist, UD and other sources.

The following is a comment from a representative of PBI Gordon, a company that produces 2,4-D products with details on safety of the newer ester formulations.

The following is an over statement "esters are the most active. Since vapour drift is a potential problem with the ester formulations, only the amines should be used on lawns, or near gardens" and very missleading. It is painted with such a broad brush and is technically inaccurate. Different products due to their potential to volatilize will carry a label statement that states that it should not be applied if the temperatures are expected to go above a set temperature like 85F. The majority of products will only state not to broadcast apply when the temperatures are above 85F. The newer longer chained esters are much lower in their potential to volatilize. We now have ester based products that volatilize no differently than amine salt formulations.What I see is more particle drift than actual volatilization. The new ride on sprayers can leave a cloud of small spray particles especially when there is minimal air movement at the time of application and then a breeze occurs and moves the cloud of small particles that were never dispersed onto off target plants.

S. Gary Custis, CPAgManager: R&D and Technical SupportPBI Gordon Corporation

Safety - Lightning

The thunderstorm season is fast approaching and workers and business owners in the green industries should take time to be familiar with lighting safety. The following are some general tips and web sites to visit.

If you can hear thunder, you are close enough to the storm to be struck by lightning. Lightning can strike as far away as 10 miles from the area where it is raining.

If you can see lightning flashes, count the seconds after a flash until you hear thunder. If that time is 30 seconds or less, the storm is within 6 miles and is dangerous. Seek shelter immediately.

The best shelters are buildings with closed windows and doors, and plumbing and electrical wiring, which provide grounding. Enclosed vehicles can also be used as shelter, but avoid convertibles. It is the metal shell of a vehicle that protects you--not the rubber tires. Roll up the windows and don't touch any metal.

Lightning can strike as far as 10 miles from the area where it is raining. That's about the distance you can hear thunder. Don't be fooled by sunshine or blue sky if a storm is approaching.

Avoid flag poles, utility poles, isolated trees, open fields, metal bleachers, metal fences, covered patios, and convertible cars. Lightning often strikes the tallest object. Metal does not attract lightning, but it is a conduit for any electrical charge. Be sure you are not higher than your surroundings or YOU could be the conduit.

If you feel the hairs standing up on the back of your neck, lightning may strike very near you in a matter of moments. Crouch down and hug your knees. If you can, balance yourself on the balls of your feet. The less contact you have with the ground the better.

Get out of and completely away from the water. Don't stand in puddles of water even if you are wearing rubber boots.

Avoid Unsafe Shelters: A shelter that does not contain plumbing or wiring throughout is not safe. Plumbing and wiring provide grounding; a small outdoor shelter may shield you from rain and wind, but it will not protect you from lightning.

Don't rely on the fact that taller objects may draw the lightning away from you. The electrical charge will likely spread out along the surface of the ground for a distance of more than 100 feet.

Wait at least 30 minutes after the last clap of thunder before leaving shelter. Don't be fooled by sunshine or blue sky! Lightning is more likely to come from the back edge of a thundercloud than from the front edge.

Visit these sites for more information.

Information taken largely from an Oklahoma State University training site on lightning safety

Friday, May 23, 2008

Nursery and Landscape - Boxwood Psyllid

Damage from the Boxwood Psyllid may be evident now. The following is information about this pest.

Boxwood Psyllid. Photo by Nancy Gregory, Extension Plant Diagnostician, UD

Boxwood Psyllid Damage. Photo by Brian Kunkel, UD Ornamental IPM Extension Specialist.

The Boxwood Psyllid, Cacopsylla busi (Linnaeus) occurs wherever boxwoods are grown. It causes the cupping of leaves and may affect twig growth, but the damage caused is purely aesthetic and not as destructive as other boxwood pests.

Plants Attacked

Boxwood psyllid is a common pest of all boxwoods, but the American boxwood (Buxus sempervirens) is most susceptible.

Insect Identification

The small, orange eggs are laid between the bud scales with only the tip of the egg protruding past the edge of the scale. The nymphs are yellowish and covered in a white waxy exudate. The

Life History

Winter: Over-winters as a tiny, orange egg deposited in the bud scales.
Spring: The eggs hatch when the buds of the host plant open. The nymphs immediately begin to feed and develop a white flocculent material over their bodies. Winged adults appear by early June.
Summer: After mating, the female deposits her eggs between the bud scales of the host plant.
There is one generation each year in Delaware.

Damage Symptoms

The nymph stage damages the host plant by feeding on newly developing foliage, causing the leaves to become cupped. This cupping conceals the psyllid, and provides protection while feeding. Damage to the host plant is purely aesthetic.

Management Options

Insecticides should be directed towards the nymph in early May before leaf cupping occurs. Formulations of acetamiprid, azadirachtin (Ornazin 3% EC only), Beauveria bassiana, bifenthrin (Bifenthrin Pro Multi-Insecticide, Talstar F, Talstar Lawn & Tree Flowable, and TalstarOne Multi-Insecticide only), carbaryl, chlorpyrifos (Dursban 50W only), cyfluthrin and imidacloprid, deltamethrin (5SC only), horticultural oil (for immature psyllids), imidacloprid, insecticidal soap, and pyrethrins and piperonyl butoxide are labeled for psyllid management. Marathon 1% G and Marathon 60 WP are labeled for use only on plants grown in containers, flats, benches, or beds.

Management Hints: Treat when young psyllids are present in early May.

Information from Penn State University. Go to to view the factsheet with images.

Landscape and Nursery - Psyllid Damage to River Birch

The following is information of psyllid damage on river birch. Psyllids or 'jumping plant lice' are small phloem feeding insects (feed on food transporting vessels in plants) and can cause considerable damage.

River birch has been recommended as a nearly problem free tree, and in most cases that is true. We have, however, had a few come into the UD Plant Diagnostic Clinic in the past couple of weeks, with psyllid damage. The damage is seen as a darkening of young terminal shoots and a twisting or distortion of the leaves, first suspected to be disease. Upon examination with a hand lens or stereoscope, psyllids and sometimes aphids were noted. Control may not be necessary. Plants can tolerate feeding and populations will decline naturally, although distorted leaves will persist. Psyllids may be controlled by spraying with neem oil, hort oil, or insecticidal soap.

Nancy Gregory, Extension Plant Diagnostician, UD

Thursday, May 22, 2008

Nursery and Landscape - Azalea Lace Bug

Azalea lace bug is the most common pest that attacks Azaleas in Delaware. The following is some information on this pest and its control.

AZALEA LACE BUG: Adults will become active by mid-late May, feeding and laying eggs on the underside of azalea foliage. Leaves appear stippled and offcolored. Look for black fecal spots on the underside of foliage or for the lacy winged adults. Spiny black nymphs will also be noticeable by the end of the month. Azaleas planted in full sun and under drought stress exhibit the worst damage. Control with acephate (Orthene) when active life stages are first seen. Note that while insecticidal soap has offered good (>85%) control, obtaining contact with lace bugs on the underside of foliage may prove daunting on small plants. Field studies have shown that Imidichloprid (Merit) will provide excellent control for at least a full calendar season. Hence, it may be unnecessary to apply Merit to the same plant every year.

Reprinted from the May 1, 2008 Edition of the Plant and Pest Advisory, Landscape, Nursery, and Turf Edition, Rutgers University.

Landscape and Nursery - Pine Sawflies

Two defoliating species of pine sawflies are of concern to landscape and nursery professionals in our area. Both species prefer two and three needled pines such as mugo, Scots, red, and Austrian. The following is some information on these pests.

The European pine sawfly has one generation per year and larvae hatch from overwintered eggs laid in slits along needles. They feed until late May or early June. The red-headed pine sawfly has two generations. It overwinters as a mature larva and then quickly completes its life cycle in early spring. The first generation occurs in May-Early June and a second generation occurs in July-August.

These sawflies are chewing insects that look like caterpillars at first glance. However, don't use B.t. to control them! Sawflies are immature wasps/hornets and are not susceptible to B.t. sprays.
A quick way to tell the difference between “maggots” (immature flies), caterpillars (immature butterflies/moths) and sawflies (most plant feeding wasps) is by looking at the number of fleshy stumps called “prolegs” present along their abdomen. All maggots and slug sawflies (i.e. rose slug, pear slug) have no prolegs. Caterpillars will have 3-5 pairs of prolegs with tiny hooks on them called “crochets” because they resemble knitting needles. Most sawflies have 6-9 pairs of prolegs and no crochets such is the case with both red-headed and European sawflies.

Control sawflies by hand removal of infected terminals or by pesticide sprays. Two reduced-risk products, Azadirachtin (Neem many trade names) and Spinosad (Conserve, Entrust) have very good sawfly efficacy. Numerous biological controls such as birds, squirrels and beneficial insects exist for sawflies and often keep their populations low naturally,

Casey Sclar, IPM Coordinator, Longwood Gardens

Wednesday, May 21, 2008

Nursery, Landscape, and Greenhouse - Wet Weather Means Slugs

Wet weather has increased slug activity in landscapes. The following is information on these pests and their control from the University of Maryland.

In wet seasons slugs and snails, invertebrates with soft bodies in the phylum mollusca, can cause major losses of plants or a reduction in the quality of plant material in nurseries and can damage plants in the landscape. The high humidity environment of production beds is well-suited for supporting populations of slugs and snails. Several native and imported slugs and snails have been reported damaging foliage of annuals and herbaceous perennial plants.

Damage to Monitor

Plant damage occurs by the rasping action of the mouthparts. Damage to leaves appears as irregularly shaped holes with smooth edges. They can chew off succulent plant parts and growing tips that are close to the ground. Seedling plants can be completely consumed. A slime trail is nearly always associated with fresh feeding injury.


Metaldehyde baits have been shown to attract slugs up to 3 feet away. The toxic effects of metaldehyde seem to be primarily due to dehydration as it elicits excessive mucus production (mucus is 98% water and 2% mucoproteins.) Thus in dry weather, metaldehyde is more effective. In wet weather, slugs sometimes can absorb enough moisture to compensate for the water lost in mucus production and therefore recover from the effects of metaldehyde. However, if slugs consume too much metaldehyde, they do not recover. Slugs seem to become more susceptible to carbamate pesticides as they mature. Copper sulfate is toxic to slugs and slugs will not crawl across a barrier of copper metal or wooden surfaces treated with copper sulfate. Mesurol is labeled for slug and snail control in greenhouses, and it also kills thrips. The problem is that Mesurol has a 24 hour REI.

Reprinted from the May 9, 2008 edition of the Greenhouse TPM/IPM Weekly Report from the
University of Maryland Cooperative Extension

Landscape - Oriental Bittersweet, an Invasive Plant

The following is information on oriental bittersweet which has become an invasive plant that you want to control on properties where it has escaped. Information is from the University of Maryland.

Oriental bittersweet, Celastrus orbiculatus, often called Asiatic bittersweet, is a deciduous woody perennial plant which grows very prolifically in this area. A problem of nursery and landscape settings, this fast growing vine can grow as tall as fifty feet or more in one year, with a stem diameter of up to four inches. The leaves will be alternate, round in shape, with a finely toothed margin. Damage from this weed can be from breakage of the desired plant as it will grow into the canopy and create either weight or potential storm damage. The spirally habit can also choke other desired plants. Oriental bittersweet is very similar to American bittersweet, and can be distinguished by the location of the flowers and fruit. Berry location on the American bittersweet is only at the tips of the vines where with the Oriental bittersweet, the berries occur all along the vines.

Oriental bittersweet is an invasive plant. One reason for concern is the color and great numbers of berries produced. As birds are one of the prime methods of dissemination, a brighter red color is very attractive to the birds and with greater numbers of berries to be found, the potential of spread is much higher. To add insult to this problem, the seeds also seem to have a higher germination percentage than that of American bittersweet. Control of Oriental bittersweet can be accomplished through either mechanical or chemical means. Cutting near the base can be effective with small plants. As plants mature, the use of a stem application after cutting with the immediate use of triclopyr (Garlon 4) or glyphosate (Roundup and others) at a 25% solution. Use caution not to apply the herbicide to the desired plant material, as thin barked species can be damaged or killed. In open settings, where possible apply triclopyr and glyphosate. If possible mow the site first to create the cut stem. Repeated applications may be necessary. The use of a basal oil and a penetrant may be beneficial to increase the effectiveness. Use eye protection when doing stem applications, as some products are salt based and may cause eye damage.

Information from Chuck Schuster in the May 9, 2008 edition of the TPM/IPM Weekly Report for Arborists, Landscape Managers & Nursery Managers from the University of Maryland Cooperative Extension.

Tuesday, May 20, 2008

Landscape and Nursery - Some Leafminers to Look For

The following is information on some leafminers that may be active in the landscape now or in the near future.

Birch Leafminer and Hawthorn Leafminer

Common lilac is in bloom and this is the time that we generally see birch leafminer and hawthorn leafminer adult activity. The insects overwintered as pupae. The adults will be searching foliage and females will oviposit into foliage over the next couple of weeks. The eggs are laid through slits in the foliage. Your customers will see blotch mines form in the foliage in June. There are 3 - 4 generations per year.

Control: European birch is most susceptible to birch leafminer. Paper birch and gray birch are also susceptible. River birch can have the foliage damaged but it is usually a few leaves and the damage is very tolerable. Systemics such as imidacloprid and dinotefuran can be applied to the soil of susceptible trees to protect foliage.

Holly Leafminers

American hollies are about 10 –14 days away from flowering. Adult holly leafminers emerge just about the time of flowering of American holly. Adults are gray to black colored flies. The adults are out for several days before they mate and females start laying eggs.

Control: Soil applications of imidacloprid (Merit in Landscape and Marathon in Nursery), thiamexthoxam (Flagship) applied as a soil drench or dinotefuran (Safari) applied as soil application gives very effective control.

Reprinted from the May 16, 2008 edition of the TPM/IPM Weekly Report for Arborists, Landscape Managers & Nursery Managers from the University of Maryland Cooperative Extension.

Greenhouse - Bacterial Blight on Geranium

The following is a short article on bacterial blight of geranium from the University of Maryland.

Geranium bacterial blight, caused by Xanthomonas campestris pv. pelargonii, was observed this week. Symptoms of this important disease of geranium include small brown leaf spots, yellow and/or brown wedge-shaped areas on the leaves, and wilting and eventual plant death. There is no cure for infected plants – sanitation and early detection are the most effective management strategies. The pathogen can be spread through infected cuttings and splashing irrigation water, and can lead to significant losses. Because other diseases and disorders can mimic bacterial blight symptoms, it is important to have symptomatic plants checked by a diagnostic laboratory. More information on this disease can be found at the following Penn State University website:

Reprinted from the May 16, 2008 edition of the Greenhouse TPM/IPM Weekly Report from the University of Maryland Cooperative Extension.

Monday, May 19, 2008

Nursery and Landscape - What to do About Fire Blight Infections

Fire blight strikes are evident in landscape plantings. Fire blight affects rose family plants, most commonly apple and pear, but also crabapple, hawthorn, mountain ash, cotoneaster, pyracantha, and spirea. What should be done with fire blight infections? The following are recommendations.

Growers and landscapers dealing with infected trees are often tempted to remove fire blight infected branches as soon as they see them. In many cases, this would be the wrong strategy, because removing branches can encourage new shoots to develop and these new shoots would also be susceptible to new infections. If fire blight strikes are discovered early, before leaves have turned completely brown, timely removal of infected shoots can help slow the spread of the disease. However, most growers do not discover the disease early enough for this to be helpful. So what is to be done with infected trees now?

Growers should just let the disease run its course, allowing the tree defenses to stop fire blight spread within the tree. Dead shoots and branches should be removed later in summer, after the plant has stopped the infection or better in winter when there is little chance of spreading the disease.

Some growers may feel compelled to cut out fire blight infections, possibly for cosmetic or aesthetic reasons. What then? If pruning is begun after obvious symptoms appear, cut back in the direction of a healthy internode of at least two-year-old wood, leaving a stub several inches long. Rely on the tree's natural defenses to prevent further movement into the branch. If needed, paint the stub with bright paint to make it more obvious. This stub can then be safely removed in the winter. Leaving infected stubs rather than pruning all the way back to the main branch reduces the chances for development of undesirable water sprouts in response to pruning.

The reason not to prune infected branches back to a spur or crotch in summer is because it may not be noticed in winter and could be overlooked. It should not be necessary to sterilize cutting tools between cuts if only blighted shoots are being removed.

Do not engage in normal summer pruning and training at the same time as fire blight removal without wiping the cutters with sterilizing solutions like Lysol, 70% alcohol or 10% bleach. Don't forget to remove the infected stubs along with dead shoots and cankers next winter.
Do not apply chemical controls such as streptomycin. They are only effective if used during the normal bloom period. Remove trailing blooms to prevent late spring and summer infections.

Fire Blight Symptoms. Photo by Division of Plant Industry Archive, Florida Department of Agriculture and Consumer Services,

Adapted from "FIRE BLIGHT-WHAT NOW?" By John Hartman in the May 31, 2005 edition of the Kentucky Pest News from the University of Kentucky, College of Agriculture.

Landscape and Nursery - Juniper Tip Blights

Twig and branch tip dieback is a common sight in many juniper plantings in Delaware this spring. While other factors can cause these general symptoms, two fungal diseases are frequently responsible for the dieback. These fungi (Phomopsis juniperovora and Kabatina juniperi) attack several species of Juniperus, including red cedar, common juniper and creeping juniper. Arborvitae is also susceptible. In the spring, Kabatina twig blight is most noticeable. The following is information on these diseases.

Kabatina Twig Blight.

Brown shoots scattered within the healthy green foliage are being seen now. The disease is especially noticeable in beds of creeping juniper. These shoots, green all winter, have only recently turned brown. In early spring, as junipers begin to green up, infected twigs from the previous season's growth begin to fade to a pale green and then turn brown in contrast to healthy green tissues nearby. Grayish lesions with numerous gray-black fruiting bodies appear at the bases of blighted shoots. Kabatina twig blight infections begin through a wound caused by insects or mechanical injury and are thought to begin the previous fall.

Disease Management: 1) Prune out and destroy infected twig tips. Pruning should be done when the foliage is dry in order to minimize fungal spread. 2) Use an approved insecticide to control insect pests. It is possible that insects, such as the juniper midge, create the wounds necessary for Kabatina infections. 3) Avoid planting highly susceptible cultivars. Instead, select varieties that are known to be tolerant to Kabatina.

Phomopsis Twig Blight.

In late spring and in summer, as new shoots are developing, they can become infected with this pathogen during periods of moist weather. This disease begins as an infection of newly developing needles which then spreads to and kills stem tissues. As with Kabatina tip blight, a tan lesion with fungal fruiting bodies (pycnidia) develop after infection.

Disease Management: 1) Fungicides can be used in spring and summer to prevent infections of new growth. Applications of fungicides containing thiophanate-methyl, azoxystrobin, propiconazole, mancozeb, or fixed copper can protect twigs from infection. 2) Prune out and destroy infected twig tips when foliage is dry. 3) Avoid overhead irrigation, especially late in the evening.

Because these two diseases are so similar in appearance, the time of symptom development can be helpful in distinguishing between the two. Kabatina twig blight symptoms generally develop early in the spring before new growth begins. Phomopsis twig blight symptoms, on the other hand, are more likely to develop any time during the growing season. If twig blight symptoms are evident now on junipers that appeared healthy in the fall, Kabatina is likely responsible.
Most junipers are not immune to tip blight diseases.

Kabatina tolerant juniper (that are not known to be susceptible to Phomopsis) cultivars across several species include: Aurea Gold Coast, Blue Mountain, Burkii, Cologreen, Emerald Sentinal, Expansa, Henryii, Hetzii, Hetzii glauca, Hibernica, Hornbrooki, Keteleeri, Manhattan Blue, Marcellus, Mas, McFarland, Mint Julep, Mountbatten, Nana, Perfecta, Prostrata glauca, Robusta Green, Saybrook Gold, Sargentii viridis, Sargentii glauca, Silver Globe, Sutherland, Variegata.

Phomopsis tolerant juniper (that are not known to be susceptible to Kabatina) cultivars across several species include Arcadia, Ashfordii, Aureo-Globosa, Aureo-spica, Buffalo, Calgary Carpet, Campbellii, Cinerascens, Depressa, Douglassii, Expansa, Fargesii, Fastigiata, Femina, Globosa, Hetzii, Hibernica, Hillii, Iowa, Keteleeri, Knap Hill, Meyeri, Mint Julep, Mountbatten, Oblonga Pendula, Pfitzeriana, Pfitzeriana aurea, Prostrata aurea, Pumila, Pyramidalis, Repanda, Reptans, Robusta Green, Sargentii, Sargentii glauca, Saxatilis, Saybrook Gold, Shoosmith, Silver King, Skandia, Suecia, Tripartita,

Avoid the cultivars Adpressa, Albospica, Alpina, Argentea, Bar Harbor, Blue Chip, Blue Haven, Blue Horizon, Blue Mat, Blue Pacific, Broadmoor, Columnaris, Emerald Sea, Emerson Creeper, Eximius, Horizontalis, Japonica, Pendula, Platinum, Plumosa Compacta, Prince of Wales, Procumbens, Sky Rocket, Spartan, Torulosa Hollywood, Variegata, Welchii, Wiltonii, and Wichita Blue.

Information from the May 23, 2008 edition of the Kentucky Pest News from the University of Kentucky, College of Agriculture.

Sunday, May 18, 2008

Turf - Summer Patch

Summer patch is a disease that we find primarily on bluegrass turf in Delaware. It starts showing up in June. Ther following is information on this disease.

Kentucky bluegrass (Poa pratensis), annual bluegrass (Poa annua), and fescues (Festuca sp.) can be affected during the summer by an interaction of environmental factors and a root and/or crown rot caused by the fungus Magnaporthe poae. This diseases is known as Summer Patch. Bentgrasses (Agrostis sp.) may also become infected but show few symptoms and may continue to perform where other grasses decline.

Summer Patch occurs between June and September. It can be difficult to diagnose this disease by symptoms alone in the early stages. The disease begins as scattered small round patches of thin, wilted or slow growing turf. Initially, affected patches may be only 3-8 cm in diameter, but thay may enlarge to about 30 cm in diameter (about 12 inches) and range from gray-green to light tan or straw-colored. In rarer circumstances, they may get to be twice that size. As patches enlarge, they may coalesce, and form crescents of yellow or tan turf. Where turf within the center of a patch begins to recover, necrotic rings may become evident.

Because Necrotic Ring Spot disease may exhibit similar symptoms, microscopic examination is often necessary to determine the cause of the problem. The roots, crowns and stolons of infected plants may appear to be dark brown as the dark mycelium of the funugus invades the tissue. As the disease progresses, the cortex may begin to rot, and plants may die.

Summer Patch blighted areas often occur on lawn sites that receive direct sun and are on south-facing slopes, or near sidewalks, driveways, buildings, or other "hot spots" or otherwise stresed areas in the yard or on golf courses. In the cool weather of autumn, the grass may begin to grow into these dead areas again. The disease, however, is likely to reappear in previously affected areas the following summer, and to increase in intensity. Summer patch usually occurs during the hotter periods (June, July, August) of the year. Summer patch is less of a problem during cool summers with adequate rainfall.

Disease Cycle

The fungus, Magnaporthe poae, survives unfavorable conditions as mycelium in infected plant tissue or plant debris. The optimum temperature for fungal growth is 28°C. Infection takes place in late spring when soil temperatures reach 19-20°C. Spread during the growing season occurs as the fungus grows between roots. Symptoms may not be evident until the temperature increases very drastically during wet weather. The pathogen may also be spread by movement of infected plant material and on mechanical equipment.

Management Strategies

The primary stresses that influence disease development include excesses of thatch, fertilizer, and turf canopy temperature, as well as incorrect timing of fertilizer applications, low mowing height, and pH extremes. Each of these stresses can be reduced through appropriate cultural practices described below. Disease severity may worsen at a higher pH, so try to maintain the pH of the soil and Rhizosphere at 5.5 to 6.0. Use an acidifying fertilizer where the pH is above 6.0, and try to avoid the use of products that may raise the pH.

For most bluegrass lawns, two to five lbs of nitrogen/1000 sq.ft. is sufficient. Apply this in a fertilizer balanced by phosphorus and potassium. Do not apply even small amounts of fertilizer during the June-August stress period because this will tend to stimulate the disease. Therefore, fertilize only in autumn (September through November) and in late spring (May). Deep watering is essential for proper root growth. Water the soil under disease-prone areas to a depth of 15 to 20 cm every 7-10 days during the dry periods of the summer. Soaker hoses are very useful for supplementary watering on steeper slopes where other sprinklers are inefficient. The harmful effects of excessive temperature can be reduced by a light sprinkling of the surface at mid-day. Proneness to disease in turf is increased as the cutting height is decreased. Cut lawns at 5 to 10 cm height, and often enough so that less than 1/3 of the leaf blade is removed during each mowing. Thatch (the layer of organic matter between the mineral soil and the green grass) should be no more than 1.5 cm (1/2 inches) in thickness. Thatch can be removed by vertical slicing machines and/or aeration during the spring and early fall. Over a longer period thatch will be reduced by using the cultural practices discussed above.

Kentucky bluegrass cultivars such as Adelphi, America, Aspen, Columbia, Eclipse, Glade, Midnight, Nassau, Parade, Ram I, Sydsport, Touchdown, Vantage, Windsor, and Victa are less susceptible to summer patch than others. Blend seed of resistant cultivars with that of one or more otherwise desirable cultivars.

Chemical treatment is efficient only when the previously mentioned cultural practices are first used. Furthermore, applications must be made before the crown rot develops sufficiently to cause visual symptoms of the disease. Fungicides containing the active ingredients azoxystrobin, cyproconazole, fenarimol, propiconazole, iprodione, thiophanate-methyl, trifloxystrobin or triadimefon are available for control of summer patch in commercial applications. Other products containing azoxystrobin, myclobutanil, thiophanate-methyl, or triadimefon may be available for use on home lawns by homeowners to manage this disease. Thoroughly water (applying 2 to 3 cm of water) areas with a history of this disease several days before applying the fungicide. To determine the best time to treat, monitor soil temperature to a depth of 2 inches, and make the first application when the soil temperature reaches 55°F. or about 13°C. Additional applications may be required for certain fungicides. Always adhere to the rates and procedures recommended on the fungicide package label.

Reprinted in part from "SUMMER PATCH ON TURFGRASS" a Cornell University Plant Disease Diagnostic Clinic factsheet

Nursery and Landscape - Newer Insecticides and Their Use.

Over the last 4-5 years, many new insecticides have been registered for use in horticultural applications. The following are some of these as well as informtion on some new uses for older insecticides.

Tristar (acetamiprid). This is a neonicotinoid insecticide available as a foliar spray for control of aphids, mealybugs, caterpillars, scales, whiteflies, thrips, leaf-eating beetles and leafminers. Nursery and landscape.

Safari (dinotefuran). A neonicotinoid insecticide used as a foliar spray or soil drench for control of whiteflies, aphids, scales, leafminers, mealybugs and other insects. Nursery and Landscape.

Celero (clothianidin). A new neonicotinoid insecticide for aphids, whiteflies and mealybugs in ornamental crops. The same active ingredient is labeled as Arena for use in turfgrass. Arena provided great control of grubs in turf, even surpassing Merit in our trials last year. Nursery and Landscape.

Discus (imidacloprid + cyfluthrin). Soil directed sprays in late June or July should be lightly covered with soil or watered-in immediately after application for optimum control of grubs. Discus is also excellent for aphid control and will help suppress scale insects and mealybugs. Allow four weeks after soil application for uptake by roots and movement into the leaves. Foliar sprays will control a wide spectrum of insects because of the cyfluthrin. Nurseries.

Flagship (thiamethoxam). Soil-directed sprays in June followed by rain or irrigation will control Fletcher scale and other scale insects and aphids. This insecticide seems to work better for soft scale insects than imidacloprid. June applications will also provide grub control, although July is the optimum timing for grubs. Nurseries

Distance (pyriproxyfen). Although not a new product, recent research tests in Indiana showed that Distance gave the highest level of control of euonymus scale of any product tested. This means it should also work well as a crawler spray for pine needle scale, oystershell scale and any armored scale insects. Nursery or landscape.

Reprinted from the June 10, 2005 edition of the Michigan Landscape Alert newsletter from Michigan State University.

Saturday, May 17, 2008

Landscape - Ticks

Workers in the landscape industry should be aware of how to deal with ticks. The following is some information on the subject.

Q: Where do ticks come from and how can I avoid them?
A: Ticks thrive in woods, uncut fields and brush. They climb onto lower portions of vegetation and attach to a suitable host passing by. To reduce tick encounters, follow these precautions:

1. Don't walk through uncut fields, brush, and overgrown areas, especially during April-July. When working in tick-infested areas, wear light-colored clothing and long pants tucked into boots or socks, and consider using tick repellent.

2. Workers should have someone inspect them after being in tick prone areas. Ticks often attach at the waist, armpit, neck and scalp, but can attach virtually anywhere. Promptly remove any ticks, using the method discussed below.

3. Keep grass and shrubs trimmed, and clear overgrown vegetation from edges of a property. Ticks and their wild hosts will not normally infest areas that are well maintained. Treating the property with insecticides is of little benefit since mowed areas are not normally infested. If insecticides are used, treatment should be concentrated mainly along borders and fences, and between overgrown areas and the lawn. A good way to confirm if ticks are present is to drag a white flannel cloth or sheet through suspected areas. Ticks will attach and be visible against the white background.

Insecticide sprays containing pyrethroid active ingredients permethrin, cyfluthrin, bifenthrin or lambda-cyhalothrin or carbaryl (Sevin) are effective. One to two applications during late April/May and perhaps mid-summer is often all that's required.

Lyme Disease

Lyme disease is a disease caused by a bacteria vectored by the deer tick. It is sometimes referred to as ‘the great imitator' since symptoms of the disease are common to many other diseases. It is initially flu-like but if not treated can develop into rheumatoid arthritis-type conditions. It is not usually fatal but can be debilitating and difficult to treat if not detected early. Humans, our pets, wild and domestic animals may get the disease.

Lyme disease is caused by a bacteria transmitted by the deer tick Ixodes dammini. This tick is found in grassy areas, open fields and especially the margin where fields and wooded areas join. Incidence of the disease is increasing in Delaware.

Description and Life Cycle

After hatching from an egg in late spring, deer ticks go through three life stages: larva, nymph, and adult. Each stage requires a different host animal. During each stage a tick feeds only once. It is a 2 year life cycle. Larvae - are very small (about the size of a pin head) and tan in color. They feed in late summer (near ground level) on mice, shrews, chipmunks, voles, and other small animals. Larvae pick up the disease bacteria feeding on an infected animal.

Nymphs are the size of a poppy seed. They are beige in color, sometimes appearing transparent with a dark head. Nymphs feed from May through August on larger animals; including birds, raccoons, opossum, squirrels, cats, dogs and human beings.

Adults ticks are tiny only the size of a sesame seed. Males are black; females have a brick-red abdomen and a black shield near the head. Females may swell to 1/4 inch when fully engorged after feeding. Adults are found from September through November, and again in March and April. Adults feed primarily on deer, but will also attack cattle, horses, dogs, etc. Human beings are accidental hosts of nymphs or adults.
Disease Cycle

The risk of being bitten by an infected deer tick is greatest in the summer months of June and July when the nymph stage is active. This is the time of year when people (and notably children) are most active outdoors. About 25% of the deer ticks in Delaware (depending on where they are found) are infected with, and able to transmit Lyme Disease. Newly hatched deer tick larvae do not initially carry this disease; they pick it up from an infected animal usually the white-footed mouse, the primary carrier/source of the Lyme Disease bacterium. After feeding, a tick that picks up the bacterium passes it to the next life stage, and is able to infect future host animals.

The early signs of Lyme Disease are:
• Headache
• Flu-like symptoms
• Spreading "bull's-eye" rash
• Swelling and pain in the joints

Lyme Disease symptoms mimic many other diseases. About 80 percent of Lyme Disease victims develop a rash at the site of the tick bite within 2 days to 4 weeks. If untreated, more severe symptoms may develop--sometimes months to years later. If you suspect Lyme Disease, consult a physician immediately.

Tick Removal

If you find a tick on your body, remove it AS SOON AS POSSIBLE. For feeding ticks, use tweezers ONLY; do NOT use nail polish, Vaseline, matches, or other methods that may traumatize the tick and cause it to regurgitate its gut contents. Grasp the tick with tweezers around its head, close to the skin and pull it outward slowly and firmly. Disinfect the bite afterwards with antiseptic.

Tick Prevention

1. Avoiding Ticks Outdoors
o Avoid tall grass and shrubby areas
o Wear slacks tucked into socks
o Wear light colored clothing (to help locate ticks easily)
o Stay close to the center of hiking trails (avoid brushing against vegetation)
o Check companions and children frequently for ticks

2. Use a repellent
• Apply to shoes, socks, and pants:
• PERMANONE* (permethrin) - kills ticks on contact - Labeled for clothing only, it will last through two or three washings.
• N,N-Diethyl-meta-toluamide commonly known as DEET. ("DEET,""Off," "Cutter," "Muskol")--repels ticks labeled for skin or clothing.

Information from the University of Kentucky and the University of Delaware.

Turf - Should You Clean or Sanitize Mowers Between Properties?

Anything that slows down the ability of a lawn care company to get from one property to another will result in reduced profits. One question that gets asked is should mowers be cleaned, washed, or sanitized between properties? The following is some information.

From time to time, the question comes up as to whether mowing equipment can transport microorganisms that cause disease (called pathogens). The answer is, "Yes, it certainly can". Inoculum is any pathogen structure that can initiate disease. Microscopic fungal spores are the most common form of inoculum in turfgrass ecosystems. Another important form of inoculum is bits of diseased grass that are cut off by the mower blade.

So if you think for a moment and imagine a microscopic fungal spore, it is easy to imagine that it can attach temporarily to the mower blade, the wheels, the carriage of the mower, etc. Furthermore, anyone who mows grass also knows that fragments of cut leaves also attach to mowers. If these cut fragments are diseased, the disease-causing agent will also be readily transported. So yes, mowers clearly can move fungal inoculum from one property to another.
Does it matter? Well, that is the key question, and the answer, at least for Delaware conditions, is "No". Most of the diseases of significance in Delaware turfgrasses are caused by fungi that are easily transported as windblown spores or are common residents of our soils. Movement of inoculum of on lawn-maintenance equipment doesn't really move inoculum any more effectively that Mother Nature already has.

In my assessment, there seems to be no reason to sanitize lawn maintenance equipment when going from one property to the next. Lawn care operators can breathe a sigh of relief, because if sanitation were biologically important to do so, I can imagine it would be very difficult to implement an effective and economical program for sanitation of mowing equipment in a commercial lawn care operation.

There can be a case made with the transport of weed seeds. If you are in the lawn maintenance business, you do not want to transport problem weeds from one site to another. Having an air tank on the truck to blow off the tops of mower decks and do quick removal of materials stuck to the the underside of mower decks can go a long way toward reducing spread of weeds. If properties are relatively weed free, this will not be necessary.

Information from "DO MOWERS SPREAD DISEASE-CAUSING AGENTS FROM ONE LAWN TO ANOTHER?" By Paul Vincelli in the May 12, 2008 edition of the Kentucky Pest News from the University of Kentucky, College of Agriculture. Comments on weeds by Gordon Johnson, Extension Agriculture Agent, UD, Kent County.

Friday, May 16, 2008

Greenhouse - Black Root Rot

Thielaviopsis root rot, also called black root rot is a problem in bedding plants such as annual vinca. It is often seen as chlorosis of young leaves and leads to losses in greenhouse and planting beds. Once established it can be very difficult to control, due to resistant spores in soil. The following is some information on this disease of greenhouse plants.

Black root rot is a common and destructive fungal disease on greenhouse floral crops. The disease is widespread, having been reported on many different plants including poinsettia, geranium, fuchsia, pansy, vincas, petunia, etc. The fungus is soil-borne and is capable of living in soils as a saprophyte (without causing disease) and surviving in soil and dust for years via tiny, thick-walled spores called chlamydospores. Plants may be infected but not show symptoms until the plant undergoes some form of stress.


Black root rot is commonly confused with Pythium root rot. Above-ground symptoms of both diseases include yellowing, stunting and under certain conditions wilting or death of the plant. Sometimes, plants affected with black root rot may have black stem lesions at or near the soil line. A close examination of the roots will reveal different symptoms for each disease. Pythium usually attacks roots from the ends or tips, causing a soft, brown rotting as it progresses. Oospores of Pythium can be seen in the infected roots with a microscope. Black root rot begins by attacking the middle of the root and forms cankers. The black root cankers can be seen relatively easily by washing roots free of growing media and then viewing them carefully with a hand lens. A plant diagnostic lab can be consulted if you suspect black root rot. Be sure and tell them you think black root rot may be involved so that the lab will examine the roots through a microscope. If Thielaviopsis is there, the black, barrel-shaped spores will be easily seen. There are also methods to culture the fungus from the tissue. Since the pathogen grows slowly onto the culture plate, culturing is rarely done in a diagnostic lab.

Causal Fungus and Disease Development

Black root rot is caused by the fungus, Thielaviopsis basicola. As mentioned earlier, the fungus is very common and widespread. It has a wide host range and affects many other hosts besides greenhouse floral crops. Thielaviopsis can spread between greenhouses or between crops within a greenhouse in many ways. Long distance spread between greenhouses occurs via the movement of infested (but not necessarily diseased) plant material. Many of our specialized plug producers control crop stresses so well that an infestation of their material goes undetected by all parties until the plants are stressed in shipment or transplanting.

Infested plugs are not the only way your crop can get black root rot. Thielaviopsis also has the potential to enter a greenhouse via wind blown dust or in growing media. Once within a greenhouse, there are many situations that can result in the pathogen becoming a long term resident. Thielaviopsis has a broad host range, and its saprophytic nature may allow it to continue to grow, spread and survive on many plants in the greenhouse that may appear symptomless or nearly so.

Thielaviopsis produces resistant "resting" spores on infected host tissue in tremendous numbers. These spores can be splashed about or blown about in dust in the air. They will be present on flats, pots, or trays that may be brought into a work area for reuse. In addition, the pathogen produces a second type of spore that is spread by splashing water. It may be the spread of these small spores that allows the disease to develop so quickly once it gets started. All in all, the black root rot pathogen is well suited to becoming a permanent, though unwelcome, resident in your greenhouse.

Disease Management

Avoid Plant Stress. Almost any factor that stresses the host plant can lead to further parasitic development of this disease. On the other hand, correcting plant stress can allow infested plants to "outgrow" the disease and eventually recover.

Crops grown under conditions that are too cool or too warm are often subject to this disease. Nutritional imbalances are also frequently associated with disease development. Excess of ammonia nitrogen appears to be particularly troublesome for pansy growers dealing with black root rot. Growing media with a pH above 5.5-6.0 are also conducive to black root rot development.

A well-drained medium provides an environment favorable for the seedling and somewhat less favorable for the pathogen. Carefully executed watering practices are very important. When the medium is irrigated thoroughly and less often, conditions at or near the surface of the medium tend to remain slightly drier and are less favorable for growth of the pathogen. Plug trays must be kept evenly moist and sufficiently warm to enable seed to germinate rapidly and seedlings to emerge promptly.


Thielaviopsis is well adapted to survival in the greenhouse. Some relatively simple practices are crucial for controlling this disease. Do not reuse containers or trays. Do not create dust, especially when the dust can settle on piles of growing media nearby. Disinfesting potting media will eliminate the organism and should be carried out if there is any topsoil or sand to be used in the growing media. Sanitize benches when possible.


There are quit a few good chemicals with efficacy against Thielaviopsis. Routine, monthly drenches at labeled rates with chemicals such as Cleary's 3336, Domain, Banner, and Terragard will help protect your crops. With bedding plants, you must have the fungicide present at seeding. Plug crops can be infected within only a few days after seeding. Continue a regular monthly schedule throughout transplanting and finishing the crop.

Reprinted from "Black Root Rot of Greenhouse Floral Crops" by Stephen Nameth, Ohio State University Extension Fact Sheet HYG-3066-96, Plant Pathology

Turf - Sulfentrazone Herbicide Injury on Tall Fescue

Sulfentrazone is a relatively new herbicide material that is sold in several products for weed control in turf. There have been reports of injury to tall fescue when using this product with urea nitrogen fertilizer. The following is an article on the subject by Dr. Steve Hart from Rutgers University.

HERBICIDE INJURY ALERT. On May 8 I was informed by my counterpart, Dr. Fred Yelverton, at North Carolina State University, that professional Lawn Care Operators were complaining that the herbicides containing the active ingredientm sulfentrazone applied in combination with urea fertilizer was causing significant injury to Tall Fescue. Dr. Yelverton has since confirmed the potential for this injury to occur in replicated research trials. As of yet I have not been informed of any injury problems with herbicides containing sulfentrazone in Delaware or New Jersey.

Sulfentrazone is currently marketed as Dismiss and is also a component of the herbicides Echelon, Surge and Q4. We have extensively tested these herbicides applied without urea fertilizer at Rutgers and found them to be safe to desired turfgrass but these studies have predominantly been conducted on perennial ryegrass and to a lesser extent Kentucky bluegrass. As of yet, we have not tested any of these herbicides on tall fescue. Until we learn more, I would recommend that these herbicides not be applied to sites containing tall fescue. If these herbicides are utilized on Kentucky bluegrass, perennial ryegrarss, or creeping bentgrass I would recommend that they not be applied in any tank-mix combination with fertilizers, other pesticides, or spray adjuvants (surfactants).

Stephen Hart, Extension Turf and Ornamental Weed Specialist, Rutgers University.

Thursday, May 15, 2008

Landscape and Turf - Salt Water Inundation Along the Coast

Coastal communitites throughout Delaware were flooded in areas with tidal surges during the recent storm. Soils in these areas were inundated with salt water. This will create saline soil conditions. The following is information on soils and salinity.

Concentrated sodium (Na), a component of salt, can damage plant tissue whether it contacts above or below ground parts. High salt levels also damage plants by osmotic effects, drawing moisture out of plants. High salinity can reduce plant growth and may even cause plant death. Care should be taken to avoid excessive salt accumulation from any source on tree and shrub roots, leaves or stems. Sites with saline (salty) soils present challenges to landscapers and homeowners.

Saline Soils

Saline soils occur when salts accumulate in the soil. Significant aline soils do occur in specific situations such as: along the coastline where seawater may overwash, and where salt from spray may collect in the soil (this happened during the recent storm; along brackish tidal rivers and estuaries. Flooding during storms and high tides can deposit salt in low-lying areas. Wooded wetlands are frequently found in these locations (again, this happened during the recent storm; and in areas with high groundwater tables where salt water has intruded from the bay or marsh areas.

How do saline soils affect trees and shrubs?

Plant root cells contain a membrane which allows water to pass through, but which prevents salt from entering. As the soil's salt content increases, it becomes more difficult for water to pass through the membrane into the root. In addition, if salt levels get high enough they may actually dehydrate roots or cause "salt burn" by drawing water out of root cells. Sodium from sea water also has direct toxic effects on many plants.

High levels of soluble salts also cause changes to soil structure, resulting in compacted soils that are problematic for plants. Because salts bind with soil clays, causing them to swell, compaction occurs more frequently in clayey soils than in sandy soils. Compaction causes reduction of pore spaces between soil particles, reducing water and oxygen penetration into the soil, and water drainage from the soil. As a result, water and oxygen availability to plant roots, and consequently plant growth and pest resistance, is affected.

Plants vary in their ability to grow in salty soils. Plants that grow only in saline soils are called "halophytic" or salt loving. Halophytic plants are generally found in coastal areas, in salt-water marshes, and in brackish (moderately saline) wetlands. The presence of some of these plants (such as spartina and sea oats) is generally indicative of a saline soil.

Most landscape plants are sensitive to soil salinity. Seedling trees and shrubs and young transplants can be particularly sensitive to salt exposure. The severity of salt damage to plants depends upon the amount and duration of exposure, and the concentration of salt. For example, coastal areas that receive consistent salt spray may always have elevated levels of soil salinity. Areas subject to flooding by brackish water or overwash from the Delaware Bay may only be affected by salinity following storms and high tides.

If there is adequate precipitation to leach the salt out of these areas soon after the initial exposure, the amount and duration of salt exposure will be brief. If salt exposure persists, or is repeated, damage will be more severe. There is a direct relationship between the amount and duration of salt exposure and potential damage to plants. The higher the amount of salt in the soil, the greater the impact on plants. Salt damage is generally more severe during periods of hot, dry weather.

Measuring soil salinity

The amount of salt in the soil can be measured with a soil test. The Delaware Cooperative Extension Service Soil Test Laboratory can test for soluble salt levels. With the exception of very salt sensitive plants, most landscape plants can tolerate salt concentrations in the medium or low ranges.

Symptoms of saline soil damage

Plant damage due to saline soils becomes evident more slowly than plant damage due to salt spray. At elevated levels, soil salts are harmful to seed germination and plant growth. General symptoms include stunted growth and reduced yields. All parts of the plant, including leaves, stems, roots and fruits, may be reduced in size. The signs and symptoms displayed by deciduous and broad-leaved trees and shrubs include leaf necrosis (death), marginal leaf or needle burn, leaf drop, and eventual plant death. Entire leaves can be affected and drop prematurely. Buds may fail to open or grow, and branches may die. Sometimes deciduous trees may exhibit early fall color and leaf drop. Salt damage on deciduous trees and shrubs usually becomes evident in late summer following the growing season, or during periods of hot, dry weather (summer drought).

On conifers (firs, junipers, pines, spruces), damage appears as brown needle tips. The brown discoloration progresses toward the base of the needles as salt exposure increases. Salt damage on evergreen trees and shrubs [both conifers and broadleaf (hollies, photinia, southern magnolia)] usually first appears in late winter to early spring and becomes more extensive during the growing season. In extreme situations, trees and shrubs will die due to soil salt damage.

When trying to diagnose plant damage, keep in mind that all of the above signs and symptoms can also be caused by a variety of other factors including root damage, drought, diseases, chemical misuse, etc. Try to eliminate these other possibilities, and use tools such as soil and water analyses, and weather data to help you arrive at a correct damage diagnosis.

Reducing soil salinity or soil salt damage

Numerous options exist for reducing salt damage including:

Improving soil structure, drainage and moisture holding capacity by adding organic matter.

Planting salt sensitive plants uphill or on berms where salty water will not drain or accumulate.

Leaching the soil with thorough irrigation after salt exposure. Flush salt through the soil by applying 2 inches of water over a 2-3 hour period, stopping if runoff occurs. Repeat this treatment three days later if salt levels are still high.

Irrigating thoroughly (deeply) rather than watering lightly (shallow watering). For established landscapes, one inch of water applied once a week is generally adequate.

Mulching to prevent evaporation and subsequent build-up of salt in the soil.

Keeping plants healthy because healthy plants are more tolerant of salt damage.

Selecting and planting salt tolerant trees and shrubs.

Adapted from "Trees and Shrubs that Tolerate Saline Soils and Salt Spray Drift"
Authors: Bonnie Appleton, Extension Specialist; Vickie Greene, Graduate Student; Aileen Smith, Graduate Student; Hampton Roads AREC, Virginia Tech; and Susan French, Virginia Cooperative Extension, Virginia Beach from Virginia Tech Cooperative Extension.