Turf - Thatch

Thatch buildup can be a problem in some turf, especially bluegrass. The following is more information.

Excessive thatch accumulation is a problem on many turfgrass sites. Thatch is a layer of organic material consisting of tightly intermingled, living and dead plant tissues derived from crowns, stems, and roots. These parts of a turfgrass plant have a relatively high lignin content. Lignin is an organic compound that is highly resistant to microbial breakdown. Accumulation of a thatch layer occurs when the production of organic material (such as lignin) exceeds the rate of decomposition within the zone between green leaf tissue and the soil surface.

To assess thatch accumulation, remove a section of grass and soil from the turf using a knife, soil probe or shovel, and measure the depth of accumulated thatch. Depths greater than 1/2 inch indicate that corrective measures may be needed to reduce the thatch layer. Measurements from several locations through the turf area are needed because of the variable nature of thatch.

A thatch depth less than 1/2 inch can be beneficial because it improves turf resiliency and wear tolerance, and insulates the soil from extremes in air temperature. However, as thatch accumulates beyond 1/2 inch, the disadvantages begin to outweigh the benefits. Excessive accumulation tends to increase the susceptibility of a turf to heat, cold, and drought stress. Localized dry spots, scalping, disease, and insects may also be enhanced by excessive thatch. Such difficulties may develop as excessive thatch accumulates because the turfgrass plants will tend to have a greater portion of their crowns, rhizomes, and roots growing within the thatch rather than the soil. A weakened, poorly rooted turf is also more prone to injury and requires increased management.

Turfgrass species differ in their tendency to accumulate thatch because they have different growth rates, growth habits, and percentage of various cell wall components (Table 1). Lignin is one cell wall component that resists microbial breakdown. Vigorous species and cultivars with high lignin content accumulate thatch more readily than those with slower growth rates and lower lignin content.


Information from "Thatch Management in Turf" Rutgers University Extension Factsheet FS740 by James A. Murphy, Ph.D., Extension Specialist in Turfgrass Mamagement

Turf - Fairy Rings

You may see circular areas of diseased turf during late summer. These are called fairy rings. The following is more information.

Fairy Rings in Turf

This disease, caused by a group of fungi known as basidiomycetes, is visible on many golf greens and home lawns in late summer. Symptoms typically appear as continuous or interrupted rings of dark-green turf. Mushrooms, which are often associated with fairy ring, usually develop in the spring and fall. Although fungicides are not effective against all species of the fungi that cause fairy ring, Bayleton, Headway, Heritage, Insignia and Prostar have provided good control in many university tests. For best results, maintain adequate soil moisture and fertility to mask symptom expression. Spike affected turf prior to irrigation and the application of fungicides to enhance water movement into the soil profile. The use of surfactants may enhance fungicide efficacy and aid in symptom suppression.

Fairy rings. Photo by Lester E. Dickens, Bugwood.org

Information taken from the August 21, 2008 edition of the Plant & Pest Advisory, Landscape, Nursery & Turf Edition, from Rutgers University.

Landscape - White Mold in Perennials and Annuals

In beds that are over-irrigated or in cool, wet periods, you can have problems with white mold in perennial and annual beds, especially in very lush plantings. The following is more information.

White mold, a disease caused by the fungus Sclerotinia, is a common problem on many vegetable crops. However, this fungus infects more than 370 species of plants, including many common landscape annuals and perennials. Ornamentals known to be susceptible are aster, begonia, daisy, delphinium, hydrangea, marigold, pansy, peony, petunia, salvia, snapdragon, and zinnia. Often, the first symptom noticed on infected plants is wilting. Upon closer inspection, a white, fluffy mycelium can be seen on infected plants. This white growth soon (in 7 to 10 days) develops into sclerotia, fungal resting structures specialized to withstand harsh environments such as winter. The sclerotia initially are white but mature as hardened, black structures ranging in size from 1/16 to 1/2 inch.

The sclerotia can be found both on external plant parts and also inside the stem. It is these structures that germinate and cause new infections in future years, so diseased plants should be immediately removed from the garden.

Other characteristic symptoms caused by this disease are water-soaked, brown lesions on stems. The characteristic white mold develops only during wet weather and often disappears as the plant dries down, leaving tan (bleached-looking) lesions and stems.

Initial infections need moisture and relatively cool temperatures to occur. However, the microclimate in irrigated flowerbeds can be ideal for disease development even in dry seasons, especially if planting densities are high. There is no control once infections have occurred; however, protective fungicide sprays of materials such as thiophanate-methyl can be effective if timed correctly. Remove diseased plants to reduce chances of infections in future years. The sclerotia can survive for 3 to 5 years in the soil, so consider planting nonhost species if an area was heavily infested.

The presence of a white, fluffy mold and dark sclerotia are diagnostic for this disease. This growth is very white and wispy, compared to the dense gray mold of Botrytis. Southern blight, a disease caused by the fungus Sclerotium rolfsii, also produces a white mold, usually present on the base of the stem. However, the sclerotia produced by this fungus are small and tan to brown in color, greatly resembling mustard seeds.

White mold in zinnia bed. Photo from the University of Minnesota Yard and Garden News.

Information taken in part from the University of Illinois, Home, Yard, and Garden Newsletter (July 17, 2007).

Landscape - Getting Hydrangeas to Turn Blue

The following is a good article on getting some Hydrangeas to turn blue in the landscape.

With so few true blue flowering shrubs for our landscape, it is no wonder so many of us are drawn to the beauty of blue hydrangeas! Only one species of hydrangea we commonly see for sale and in our northern landscapes include cultivars that can be coaxed to bloom a true blue or, if desired, a pure pink. It is Hydrangea macroplylla which is also known as the bigleafed hydrangea. Endless Summer® is the most common cultivar of this hydrangea we see for sale in the north as it is able to bloom off of both old and new wood. This is unlike most other H. macrophylla cultivars which bloom on only old wood.

So, what makes bigleaf hydrangea turn blue , pink, or a shade in between? The primary contributor is soil pH. Soil pH ultimately influences the pH within the plant cells. The critical part of the plant cells for pH and color are the large watery vacuoles within the bract cells (colorful portion around the small true flowers that look like petals). The pH in the vacuoles influences the configuration and how light reflects to our eyes from the pigment anthocyanin. Anthocyanin is a plant pigment that ranges in color typically between blue and pink and can appear cream or colorless in the transition between blue and pink. The color the tissue appears depends on the pH of the cellular fluid and also other factors including presence and association of metal ions such as aluminum. There are multiple anthocyanins and they all share a common core chemical structure and are distinquished by placement of side chains and sugars connected to the core structure. Different anthocyanins have slightly different properties and color ranges. Different plant species and even cultivars within a species can have a different types of anthocyanins and different relative concentrations. Anthocyanins generally appear more towards the blue end of their range when the cellular pH is more alkaline (or higher in number) and more pink when the cellular pH is more acidic or lower.

What??? Doesn't this seem counterintuitive and contradictory? We have been told to lower the pH of the soil we have our hydrangeas planted in with elemental sulfur or aluminum sulfate to make the bracts turn blue and the opposite with lime or gypsum to make them turn pink. Interestingly, the pH within the vacuoles of petal cells moves the opposite direction as the pH of the soil. So, in order to raise the pH within the vacuoles of bract cells and make our hydrangeas turn blue, we actually lower the pH of the soil around our plants and visa versa for pink.

Bailey Nurseries, the introducers of Endless Summer® produces tens of thousands each year and most of them are grown and sold with blue flowers. There are actually three different cultivars in the series now and they all share the ability to bloom on both old and new wood. There is Endless Summer® original, Endless Summer® Blushing Bride, and now the latest addition, Endless Summer® Twist and Shout. For the Endless Summer® original being coaxed to turn blue, the flowers first appear white and then turn blue from the outside of the large colorful bract inward towards their middle until the whole bract is blue. A question arose if it would be possible to make the petals color up and turn blue sooner (being white for less time). Doing so would reduce production time. In order to work towards answering this important question, we started by doing a series of bract pH tests to understand if bract pH is consistent during expansion and coloration or if it changes and is the trigger or somehow associated with when the bract can turn blue.

We collected mature and immature heads of Endless Summer ® original from plants grown to be pink and other plants being grown to turn blue. We also collected heads of Endless Summer® Blushing Bride (it is a cultivar that has a little bit of blush to it and is stays primarily white). Throughout our bract pH tests, we took a uniform amount of bract tissue and put it in distilled, deionized water. We spun it at 14,000 rpm in a centrifuge. This very fast motion broke the cells and allowed the liquid content within cells to mix with the purified water. After spinning in the centrifuge it was amazing to see the bracts holding their form, but appearing clear or white no matter what color they started as. The solution then appeared the color of the bract before we spun it. We tested the pH of the solution with a standard pH meter.

We sampled fully expanded pink and blue bracts of Endless Summer® original. The solution from the blue bracts had a pH of 6.10 and the pink bracts 5.94. We also took immature florets of Endless Summer® original that were white at the base and their tips were starting to turn blue. We cut a number of small florets separating the white bases from the blue tips and measured the pH of bract tissue of these different colors separately. The white bases were a pH of 5.59 and the blue tips were 5.84. Therefore, for the Endless Summer® original grown to be blue with low soil pH, we saw a clear transition in pH from 5.59 for the white base of an immature bract to 6.1 when the bract was fully blue and mature. We didn't explore all the same stages and color transitions for Endless Summer® original grown to be pink. This is something worth pursuing in the future. It is interesting the pH of a mature pink floret was 5.94. This strangely happens to be a higher pH than that of the blue portion of a bract as it first began to turn blue (5.84).

We also decided to look at the pH in Endless Summer® Blushing Bride. This hydrangea does not turn blue or pink even when pH is altered. It likely produces very little anthocyanin in general and therefore basically remains cream to white regardless of pH. The sample taken from young expanding bracts of Endless Summer® Blushing Bride were a pH of 5.82 and the fully expanded florets were 5.96. A trend of an increase in bract pH was also observed in Endless Summer® Blushing Bride as it matured. The pH of a mature bract of Endless Summer® Blushing Bride was intermediate of that of mature bracts of pink (5.96) and blue (6.1) Endless Summer® original.

In the end this initial experiment helped us learn that there is a strong and clear association with blue bract color and bract pH in Endless Summer® original. The blue color seems to go hand in hand with an elevated pH as it starts out white, begins to turn blue, and then matures as a stronger blue. A subsequent question we would like to answer is if anthocyanin is already present in the white bract tissue and cannot turn from white to blue until the petal pH is further elevated, or if anthocyanin is just not present in the white tissue yet and is synthesized at the point in bract development when we typically begin seeing blue coloration. If the latter is true, it is likely that we cannot speed up blue coloration of bract tissue in Endless Summer® original. The limiting factor in that case won't be the pH, but when anthocyanins are synthesized.

The next steps in this study would be to directly test for anthocyanin pigment in different aged bracts to learn when it is synthesized as well as to possibly do some simultaneous tests growing Endless Summer® original hydrangeas in a range of different low soil pH's. Growing plants in a range of different low soil pH's would be the most direct way to see the effect on coloring rate of florets based on soil pH and also to learn the effect of such pH levels on overall plant growth.

Reprinted from "Getting Hydrangeas to Turn Blue" by David C. Zlesak and Gail Soens, University of Minnesota Extension Educator and Bailey Nurseries New Variety Coordinator / Section Grower Bud and Bloom Hydrangeas & Roses in the University of Minnesota Yard and Garden News http://blog.lib.umn.edu/efans/ygnews/2009/08/

Landscape - Cercospora Leaf Spot of Hydrangea

The following is information on Cercospora leaf spot of Hydrangea which is now present in the landscape.

Cercospora leaf spot on hydrangea is appearing in the landscape again. The irregular purple to purple- rimmed spots with gray centers infect both Hydrangea macrophylla and Hydrangea quercifolia. With lots of rain or overhead irrigation, this fungus disease can cause spotting that detracts from the overall appearance of the plants. If defoliation occurs, which does not happen often, plant health can be compromised. Most of the time fungicides are not warranted.

Fallen diseased leaves are the primary source of spores of the causal fungus Cercospora hydrangeae. These spores are spread to the healthy lower leaves by splashing water. Once C. hydrangeae is introduced into a planting of hydrangea, yearly outbreaks of this disease are likely to occur. Frequent late summer rain showers will not only greatly increase the rate of disease spread, but also intensify the level of leaf spotting and defoliation. Extended periods of drought will usually suppress disease development and spread.

In the landscape and container nursery, removing dead diseased leaves, applying enough nitrogen to maintain a moderate growth rate, and surface watering will help slow the development and spread of Cercospora leaf spot. Since the appearance of symptoms is usually delayed until late summer to early fall, protective fungicide sprays are rarely needed for the control of this disease on hydrangea in the landscape or nursery. For effective control of Cercospora leaf spot with a fungicide, begin applications when spotting of the leaves is first seen and continue applying that treatment as needed. Typically, protective fungicide treatments are suggested only on highly valued plants that suffer noticeable damage every year. Fungicides registered for the control of Cercospora leaf spot include azoxystrobin, chlorothalonil, myclobutanil, and thiophanate-methyl.

Cercospora on Hydrangea. Photo from the University of Arkansas.

Information from Bob Mulrooney, Extension Plant Pathologist, UD and "Diseases of Hydrangea" by Austin K. Hagan, Extension Plant Pathologist and Professor, and Jackie M. Mullen, Extension Plant Pathologist and Diagnostician, both in Entomology and Plant Pathology at Auburn University.

Landscape, Nursery, and Greenhouse - Neem Based Products

The following is information on products from the neem tree that are used for insect and disease control.

Neem pesticides are derived from seeds of the neem tree (Azadirachta indica syn. Melia azedarachta a relative of the mahogany tree), a subtropical shade tree growing or cultivated in many developing nations. Many different forms are available commercially and knowing what's out there can really help. Seed extracts (oils) are common and may contain certain insecticidal ingredients. Soaps or just the general seed oil are also available.

Neem pesticides containing azadirachtin (AZA) kill insects by disrupting their growth and development. They are also strong insect repellents. Neem products with AZA control a broad range of pests, providing superior control of chewing insect pests such as caterpillars, leaf beetles, and sawflies. The amount of AZA present in a formulation varies and may reflect whether the product is a Ready-to-Use (RTU) formulation or a concentrate. Commercial applicators can buy AZA containing brands such as Azatin, Azatrol, Azamax, etc. Home Garden trade names include Safer BioNeem, Neem-Away Insect Spray, and others.

Clarified hydrophobic extracts of neem oil are products that do not contain any AZA and are similar in use pattern to insecticidal horticultural oils and powdery mildew fungicides. Trade names include Green Light Neem Concentrate, Trilogy, and many others. This is the type most often found on retail store shelves.

Fatty acids from neem seed are insecticidal soap (potassium salt fatty acid)/neem blends that vary in their concentration of AZA and should be used with the same care as any insecticidal soap. Trade names include Bon-Neem and Organica K+ Neem.

Many neem products carry OMRI listings that also allow them to be useful tools in organic production. Formulations (particularly those with AZA) provide a level of pest management equal to that of many synthetic counterparts from a botanical source.

Information from Casey Sclar, IPM Coordinator, Longwood Gardens

Landscape - Daylily Leaf Streak

The following is information on daylily leaf streak, a disease of daylilies now present in the landscape.

Daylily leaf streak has made a real resurgence during this hot, humid, rainy period the last couple of weeks. The foliage will get diffuse brown spots and develops into long steaks of dead tissue bordered by yellow tissue. The old dead leaves will make the plants look unsightly until the weather changes and new healthy leaves replace them later in the month. This is a fungus disease caused by Aureobasidium microstictum. Avoid damage to the leaves, which is one of the ways it enters the plant. Avoid highly susceptible varieties and limit overhead irrigation. Fungicides can be helpful if applied preventatively (before symptoms appear). I have had success with some of the triazole fungicides such as myclobutanil (Systane, Eagle, Immunox) and Banner MAXX.

Daylily leaf streak. Photo by Tom Creswell, Purdue University.

Information from Bob Mulrooney, Extension Plant Pathologist, UD

Turf and Landscape - pH Management

Managing pH is one of the most important aspects of soil fertility and soil health in turf and landscapes. As fall planting season approaches, take measures to assess soil pH and ammend soils as needed.

Late summer/fall planting season for turfgrasses, perennials, and cool season annual beds is coming up. It is important to not to forget pH management as you prepare soils for planting. If you have not done so already, take soil samples from areas to be planted and send to an accredited lab (such as the UD Soil Testing Lab) for pH and mineral nutrient testing. The test results will provide information on lime requirements – both rate and type of lime to use for standard plantings (or soil acidifying requirements for acid loving plants).

Most woody plants can tolerate a wide range of pH’s; however, perennials, annuals, and turfgrasses are more sensitive to pH. For the majority of these plants the ideal pH range is 6.0-6.5. If pH values are below 5.3 root growth will be impacted, toxic levels of Aluminum and Manganese may be present, and you may see deficiencies of Magnesium and Calcium. If an area has been over-limed in the past and the pH is above 6.8 you may see micronutrient deficiencies such as Manganese or Iron (especially in turf). For acid loving plants (blueberries, Azaleas, Rhododendrons) that thrive in pH’s below 5.4, elevated pH can result in poor growth and micronutrient deficiencies.

Gordon Johnson, Extension Agriculture Agent, UD, Kent County.

Weather - August Rainfall

We have had considerable rainfall over the first 2 weeks of August across mid-state. The following are some August rainfall totals:

Blackbird = 2.20 inches
Bridgeville = 1.56 inches
Dover = 1.01 inches
Ellendale = 1.49 inches
Georgetown = 1.14 inches
Harrington = 2.17 inches
Kitts Hummock = 1.45 inches
Milford = 3.19 inches
Sandtown = 1.11 inches
Smyrna = 7.06 inches
Townsend = 0.31 inches
Viola = 2.21 inches

As you can see, rainfall still is extremely variable. Smyrna continues to receive significant rainfall. However, not far away in the Townsend area there has been little rain. Milford also has had considerable rainfall this month.

The humid, wet weather along with heavy dews have set up conditions for many diseases in ornamental plants and turf. For example, we are seeing more downy mildews this year and Pythium in turf.

Gordon Johnson, Extension Horticulture Agent, UD, Kent County

Greenhouse and Nursery - Fascination Growth Regulator and Mums

In cases where mums are too short or compact late in the season is there any remedy? You might try the growth regulator Fascination. The following is more information.

Some growers have asked about using Fascination [a cocktail of two plant hormones, gibberellic acid (GA4+7) and benzyladenine (BA) in equalproportions] to increase plant height. Fascination increases height by stretching the distance between the leaves. Trials using Fascination on poinsettias have shown that it will stretch soft tissue about an inch per application. Response is quick, within one week of application you will know how much additional growth the treatment produced. Application can be repeated as needed but results are best when shoot growth is still soft and several of the upper internodes have not yet expanded. Once stems harden they will be less responsive to treatment and late treatments may just cause the flower buds to stretch above the foliage. Trials using Fascination on garden mums has been minimal at this time but preliminary results show increased stem length with a 10ppm spray application.

For more information (and photo) of Fascination on mums: GroLink July Newsletter
http://www.grolink.com/pdf/Belgian%20Mums%20Newsletter%20July%202009.pdf

Information from the current New England Greenhouse Update posting http://www.negreenhouseupdate.info/index.php/updates

Landscape - Saddleback Stinging Caterpillars

One common stinging caterpillar you may encounter this time of year is the saddleback caterpillar. I have been "stung" many times by these critters when working in corn research plots in Maryland in the past. They are also found in the landscape. The following is an article on the subject from the University of Kentucky.

Caterpillars are tasty morsels for predators so many species rely on camouflage to stay off the menu. Those that can protect themselves, stinging caterpillars for example, stay in plain sight and advertise with bright or distinctive markings. They are covered with sharp, brittle bristles that break off and stick in the skin like so many cactus spines. Unfortunately, that’s not all, the bristles are hollow and contain an irritating substance that produces a very unpleasant skin reaction.

Saddlebacks are relatively common and are among the most venomous species in North America. A full grown caterpillar is brownish red, about 1.25 inches long, and has several distinctive characteristics which include two fleshy horns studded with spines on each end, shorter armed bumps along both sides. The back carries a bright green "blanket" trimmed in white, with brown-to-purple central spot or "saddle", also trimmed in white. Saddlebacks occur on many plants including apple, basswood, cherry, chestnut, dogwood, elm, maple, oak, plum, and even corn. They are most abundant at this time of year.

A brush with a saddleback results in immediate pain followed by swelling and blistering if the spines are not removed. The irritation should be gone in 8 hours or less if the spines are removed. They can be stripped cellophane or adhesive duct tape. Wash the area with soap and water and apply an ice pack to relieve the irritation. Contact a physician immediately if the irritation does not subside of if other symptoms appear.

More information on stinging caterpillars is available in www.ca.uky.edu/entomology/entfacts/entfactpdf/ef003.pdf

Saddleback caterpillar. Photo by Herbert A. "Joe" Pase III, Texas Forest Service, Bugwood.org


Reprinted from "Caterpillars That Pack a Punch" By Lee Townsend in the current edition of the Kentucky Pest News from the University of Kentucky http://www.uky.edu/Ag/kpn/kpn_09/pn_090811.html

Greenhouse and Nursery - Mum Premature Budding and Short Plants

The following is information on premature budding in mums and why plants may be shorter than normal from the New England Greenhouse Update.

Premature budding.

Chrysanthemum flower buds initiate easily and develop rapidly, especially if plants are stressed in any way. Lack of adequate fertilizer and cool nights are causes for premature budding. When grown outdoors, we are relying on natural daylength and temperature to control the timing of the crop. Chrysanthemums are short-day plants. Both flower initiation and development of the flower buds occur more rapidly under short days than in long days. However, temperature has a greater influence than daylength on flowering of garden mums. With several cool nights in a row, garden mums can initiate many buds prematurely which results in early flowering of plants.

Short plants.

Again, short plants are a result of plants setting bud too early. In chrysanthemums, flower bud initiation marks the end of vegetative growth. Garden mums initiate leaves rapidly. Cool weather early in the growing season will reduce the number of leaves formed on each shoot, thereby, resulting in plants with fewer nodes and shorter plants. Another reason for smaller, harder plants may be due to lack of nutrients. Frequent rain made it difficult to keep plants fertilized. As a result, nutrients were leached and plants stopped growing.

Information from the current post on the New England Greenhouse Update Webpage http://www.negreenhouseupdate.info/index.php/august/445-chrysanthemums-early-flowering-and-short-plants

Landscape - Diagnostic Technique Mini-Seminar

The following is information on an upcoming program on practical diagnostic techniques for landscape managers in Maryland.

Practical Diagnostic Techniques (and more!) for Landscape Managers

Date: Wednesday, September 16, 2009
Time: 9:00 am - 1:00 pm
Location: Dave & Busters, White Flint Mall, Kensington, MD
Directions: Dave & Busters is located on the top level of White Flint Mall in Kensington
Registration: MDPREPAYMENT IS REQUIRED FOR ADVANCED REGISTRATION. CANCELLATION POLICY- Cancellations received by September 11th will receive a full refund. No refunds will be given after September 11th. No refunds due to inclement weather.
Go to http://www.lcamddcva.org/memform/september09.cfm for online registration.

Enhance your skills in disease and insect diagnosis-and low risk control methods. Join other landscape managers and gain practical information and skills you can put to use everyday!

9:00 - 9:45 Practical Diagnostic Techniques for Landscape Managers in Landscape Disease Problem Solving. Karen Rane, Director of the Plant Diagnostic Clinic and Extension Plant Pathologist, University of Maryland

9:45 - 10:15 How to use a dissecting scope to examine scale, tree borer and nematode samples. Karen Rane, Suzanne Klick, Stanton Gill and Jeff Gabric

10:15 - 10:30 Coffee break - chance to visit exhibitors

10:30 - 11:15 Scales and borers are two of the most destructive pests of landscape trees and shrubs. Learn how to identify major armored and soft scales and determine when they are most susceptible to control options. Landscape plant material has suffered from a great deal of tree borer damage in 2009. Learn how to identify and monitor the major tree borers, and discover control options. Stanton Gill, Extension Specialist in IPM and Unit Coordinator, University of Maryland Extension

11:15 - 12 Noon Learn how to mix, apply and evaluate the efficacy of beneficial nematodes, and how to make beneficial nematodes work in an IPM or organic approach to landscape management. Jeff Gabric, Becker Underwood, Nematode Field Development Specialist, Becker Underwood Company of England

12 Noon Lunch, networking and chance to visit exhibitors

Program sponsored by the Landscape Contractors Association of MD-DC-VA

Landscape, Greenhouse, Nursery, and Turf - New Insect Control Products

The following is information on some new insect control products available for use in the horticultural industry.

New Products for Ornamental Greenhouse, Nursery, and Landscape Pests

A new product Kontos is available to manage most sucking pests in greenhouses. It is also labeled for use in nurseries. Kontos from OHP is effective against whiteflies, aphids, mealybugs, thrips, and other insects. Kontos has a unique mode of action (IRAC group 23) that makes it an important tool in resistance management programs. This could be particularly important as a product to rotate with Conserve (spinosad) to kill thrips. It is also soft on beneficial organisms. More information on Kontos can be found at: http://www.ohp.com/PIB/PDF/kontos_490_pib.pdf.

In ornamental landscapes we now have Acelepryn by Dupont. This unique chemical has a very low vertebrate toxicity. So low in fact that it does not require a signal word on the label. It is effective on many landscape pests and can be used as a foliar spray or drench to provide translaminar and systemic plant protection. Acelepryn also is soft on beneficial organisms compared to older products. More information about Acelepryn can be found at http://www2.dupont.com/Professional_Products/en_US/assets/downloads/pdfs/H65676.pdf.

As new products become available it is important to begin incorporating them into insecticide programs. These products are less toxic to vertebrates, pollinators, and beneficial insects than products such as organophosphates and pyrethroids. They can also help reduce development of resistance and prolong the effective life of other products.

Reprinted from the current issue of the North Carolina Pest News http://ipm.ncsu.edu/current_ipm/09PestNews/09News17/pestnews.pdf

Turf - Pythium Blight

We sometimes see Pythium blight in our turfgrasses in Delaware during hot humid and wet weather. The following is more information.

Pythium Blight

With the recent hot, humid weather, Pythium blight has been reported on golf and landscape turf. Pythium thrives in low or poorly drained areas, especially when the night temperatures are above 68 to 700F. For best results, improve drainage, water in the early morning hours (midnight to 8 am), avoid over-fertilization, and apply Alude, Banol, Chipco Signature, Disarm, Headway, Heritage, Insignia, Koban, Magellan, mancozeb, Prodigy, Quell, Segway, Subdue MAXX, Terraneb SP, or Terrazole, according to the manufacturer’s recommendations. Caution: Koban and Terrazole can be phytotoxic during hot weather, so follow label directions carefully and experiment on a small area before treating large areas if using either product at this time of year.

Lawn infected with Pythium blight. Photo by William M. Brown Jr., Bugwood.org.

Information from Bruce B. Clarke, Ph.D., Specialist in Turfgrass Pathology, Rutgers University from the July 23, 2009 edition of Plant & Pest Advisory, Landscape, Nursery & Turf Edition from Rutgers University.

Landscape, Nursery, and Greenhouse - Perfect Year for Downy Mildews

This has been the perfect year for downy mildews in ornamental plants. The following is more information.

Symptoms

Symptoms of downy mildew most often appear on the upper leaf surface as a patchy yellow, purple, or brown discoloration bounded by leaf veins. Affected leaves may defoliate prematurely, and stunting may also occur in some species, such as snapdragon, and in seedlings and bulb crops. To see why the disease is called “downy mildew,” turn the leaf over. Evident on the lower leaf surface are the characteristic downy tufts of white to purple/grey fungal growth. This growth consists of spores (called sporangia or conidia) that are easily dislodged and disseminated by wind and splashing water.

Disease development

Downy mildews develop on susceptible crops during cool (58 to 72ºF), fairly humid (> 95% RH) conditions when spores from previously infected tissue are splashed or blown by air currents to colonize new sites. As infection progresses, symptoms develop, and the downy tufts of spores associated with leaf lesions may appear on the lower leaf surface. Fungal development ceases for most downy mildews when weather becomes dry and warmer than 80ºF for 24 hours. In the absence of susceptible plant tissue, downy mildew pathogens in cold climates survive in plant debris, soil, or weeds. Watch closely for symptoms in susceptible crops during periods of cool, humid weather. When you see foliage that is discolored, turn the leaves over to check for mites or downy mildew sporulation. Symptoms of this disease can be confused with other fungal (such as Botrytis blight and powdery mildew) or bacterial diseases, foliar nematode, or some nutritional deficiencies.

Disease management

To manage downy mildew, first “manage the moisture”: space plants to ensure good air circulation and rapid drying of foliage after irrigation. Avoid overhead irrigation when the weather is generally cool. In greenhouses, reduce relative humidity to less than 85% by, again, properly spacing plants, and use horizontal air flow fans to improve air circulation throughout the house. Fill the house with warmer, drier air by venting and heating two or three times per hour at dawn and at dusk. Practice good sanitation techniques. Discard all diseased plants as well as plant debris that may harbor spores, and control weeds that may be another source of downy mildew inoculum. Protect susceptible crops during cool, wet weather with preventive fungicides. Active ingredients labeled for control of this disease include azoxystrobin, Bacillus subtilis, copper, dimethomorph, fosetyl-Al, kresoxim-methyl, mancozeb, phosphite, trifloxystrobin, and triadimefon + trifloxystrobin (Armada). To reduce the possibility of the development of fungal resistance to some of the newer systemic fungicides with single or few modes of action, rotate these chemicals with protectants such as mancozeb. Avoid the sole use of any fungicide for extended periods of time when other reliable products are available, and refer to label for timing, host plants, and rates.


Information reprinted from "Downy Mildew in Ornamental Plants" by Ann B. Gould, Ph.D., Specialist in Plant Pathology, Rutgers University in the July 23 edition of the Plant and Pest Advisory; Landscape, Nursery, Turf edition. Information Source: Gleason, M. L., M. L. Daughtrey, A. R. Chase, G. W. Moorman, and D. S. Mueller. 2009. Diseases of Herbaceous Perennials. APS Press, St. Paul, MN.

Landscape - Current Pests

The following are some current pests active in Delaware landscapes.

Pine needle scale 2 crawlers are actively searching for places to settle and feed. They are active around 1622-2745 [2053 peak] GDD Base 50. Some treatment options include: horticultural oil, insecticidal soap, dinotefuran, acetamiprid, and pyriproxyfen.

White prunicola scale crawlers are also starting to become active this week.

Cicada killers are actively flying about defending territories, paralyzing cicadas, and scaring people. Treatments are seldom warranted because these nonsocial non-aggressive wasps seldom sting.

Catalpa caterpillars are feeding in New Castle County. Smaller (younger instars) can be controlled with B.t., but larger caterpillars may need spinosad, chlorantraniliprole, acephate, or synthetic pyrethroid.

Information from the current Ornamentals Hotline Newsletter from the University of Delaware Cooperative Extension.

Landscape - Oystershell Scales

Be on the look for oystershell scales in the landscape. The following is more information.

Oystershell scales feed on ash, cotoneaster, dogwood, maples, willow, popular and many other trees and shrubs found in the landscape. This scale attaches to twigs, branches, and trunks and feeds on surrounding cells sucking out sap and killing them. Heavy infestations may encrust branches and cause stunting, yellow foliage, bark cracking and branch dieback.

Pennsylvania reportedly has one generation a year, but research conducted by the Penn-DEL research group found two generations st present: 1 generation crawlers at 305-799 [445 peak] GDD base 50 and 2 generation crawlers at 2113-2259 GDD Base 50. The scale is light to 50 dark brown or gray and oyster-shaped in appearance. Adult females are white, crawlers are white to light yellow, and eggs (overwintering stage) are white.

Lady beetles, predatory mites, and parasitoids attack crawlers and adult oystershell scales. Prune out heavily encrusted branches to reduce infested plant material and reduce future crawler populations. Some chemical control options include: horticultural oil or insecticidal soap during crawler activity, acetamiprid, dinotefuran, azadirachtin, acephate or a pyrethroid (e.g., deltamethrin) are other products available for effective scale management.

Oystershell scales. Photo from the United States National Collection of Scale Insects Photographs Archive, USDA Agricultural Research Service, Bugwood.org

Information from Brian Kunkel, Ornamental IPM Specialist, UD.

Compost Use Considerations

The UD IPM program has an extension project looking at the effect of compost on soil health. While this project is focusing on vegetable crops, some initial observations can equally apply to evaluating compost for ornamental and turf usage. The following is more information.

We are evaluating 3 different composts, an agricultural grade compost made specifically for improvement of field soils, a yard waste based compost, and spent mushroom soil compost. These were applied at a ½ inch rate and 2 inch rate and then mixed into the soil. Plant performance and soil quality measurements are being evaluated and compared to fumigated soil and untreated controls

The Ag grade compost was hard to apply due to the high moisture content; whereas the yard waste compost spread easily (well screened and appropriate moisture). Plant performance in the Ag grade compost has been excellent at both rates; the yard waste based compost has shown signs of nitrogen deficiency especially at high rates; and the spent mushroom soil based compost has showed signs of salt injury in the high rate treatment but good growth in the low rate treatment. These observations illustrate the need to evaluate compost sources before application. Some critical factors to consider are compost maturity, C:N ratio, salt content (EC), nutrient composition, pH, partical size and uniformity, moisture content and weight. In these studies the ag grade compost was fully mature, had moderate levels of nutrients, and a low salt content. The yard waste based compost was not mature (thus the N deficiency), had low nutrient content, and low salts. The spent mushroom soil compost was not well screened, had high nutrient content, but also had high salt levels.

Gordon Johnson, Extension Agriculture & Horticulture Agent, UD, Kent County

Greenhouse and Nursery - Chrysanthemum White Rust

Chrysanthemum White Rust has been found in Delaware. The following is more information.

CHRYSANTHEMUM WHITE RUST FOUND IN DELAWARE ON 7/23/2009.

Chrysanthemum white rust caused by the fungus Puccinia horiana affects cultivated chrysanthemum plants in the Family Asteraceae. The disease is not established in U.S, and could have significant impact on chrysanthemum production. Therefore, the pathogen, P. horiana, is a USDA/APHIS reportable pathogen. The disease has occasionally been found in Delaware, but in cooperation with USDA and Delaware Department of Agriculture, it has been easily detected and eradicated. It has recently been determined that the fungus may survive over the winter season in infected plantings of hardy mums. Symptoms include yellow spots on the upper surface of the leaves that are up to 5 mm in size. On the underside of the leaves, raised bumps or pustules develop which have a waxy, warty appearance and are light in color. If you see symptoms of white rust on a plant purchased or in established plantings in Delaware, please take it to your nearest County Extension Office, the UD Plant Diagnostic Clinic, or contact DDA, Bureau of Plant Industry. Plants should be destroyed.

Chrysanthemum White Rust. Photo from the Division of Plant Industry Archive, Florida Department of Agriculture and Consumer Services, Bugwood.org

Information from, Nancy Gregory, Plant Diagnostician, UD

Landscape - Lacebug Feeding Damage

We are seeing considerable lacebug feeding damage in Delaware landscapes at this time. The following is more information on the subject.

Lace bugs use their sucking mouthparts to feed on plant sap. Damage ranges from a few scattered tiny white to yellow spots on the upper surfaces of leaves to bleached white leaves that drop prematurely in late summer. Lacebugs commonly feed on azalea (azalea lace bug); hawthorn, cotoneaster, pyracantha, Japanese quince (hawthorn lace bug); rhododendron and mountain laurel (rhododendron lace bug); and ash, hickory, mulberry, and sycamore (sycamore lace bug). Lace bugs can be confirmed as culprits by looking at the undersides of spotted leaves for the insects, white cast skins, tarry waste spots, or eggs (larger dark spots along leaf midribs). The adult is about 1/8 inch long with lace-like wings that cover the abdomen. Nymphs are dark and spiny.

Tolerate light to moderate damage as much as possible; often the plant is not harmed by these insects. Prune damaged foliage if practical and follow sound practices to promote plant health. Insecticidal soap and horticultural oils can be used for control with minimal impact on natural enemies; most other insecticides will provide control, as well. Thorough spray coverage to lower leaf surfaces is necessary with all products.

Lace wing eggs are inserted into plant tissue so they are protected from sprays. Consequently, more than one application may be needed for control. These applications must be made at the first signs of leaf spots to be effective. A soil drench with an imidacloprid product can provide good preventive control where chronic infestations are a problem. The drench should be applied in the spring according to label directions.

Azalea lacebug adult. Photo from the Pest and Diseases Image Library, Bugwood.org

Azalea lacebug damage. Photo by Whitney Cranshaw, Colorado State University, Bugwood.org

Information from Lee Townsend in the current edition of the Kentucky Pest News http://www.uky.edu/Ag/kpn/kpn_09/pn_090804.html

Landscape - Wetwood and Slime Flux Disease of Trees

The following is information on wetwood disease and slime flux in trees

Wetwood disease and its associated product, slime flux, may be seen in landscape trees this summer. The sometimes foul-smelling and unsightly seepage from wounds in the bark or wood of various shade trees is known as slime flux. It occurs most commonly on bacterial wetwood-infected trees, such as elm, mulberry, poplar, oak, birch, and maple. Although slime flux development is seasonal, evidence of wetwood and slime flux-stained bark is visible anytime.

Symptoms and Cause.

Tree owners will first notice a vertical streak of wet bark on the trunk beginning at a crack or wound up on the trunk and extending all the way to the ground. This seepage is often accompanied by a discoloration of the bark in the area where the fluid flows. Wetwood seepage originates from infections of the heartwood and inner sapwood by common soil-inhabiting bacteria such as Enterobacter cloacae (Erwinia nimmipressuralis). There are many other bacterial species also associated with wetwood. Wetwood bacteria are capable of growing anaerobically (without oxygen) in the internal wood tissues of the tree and leaving the wood of trunks, limbs, and roots water-soaked. Methane and osmotic or metabolic liquids, two by-products of the bacterial activity, accumulate under pressure and are forced out of the tree through the nearest available opening, usually a trunk wound or branch stub. Pruning a branch or taking a core with an increment borer can sometimes release the materials under pressure, squirting the worker with foul-smelling liquid and gas.

Normally flowing to the wounded bark surface, the wetwood fluid is a clear watery liquid containing several nutrients. On the surface it soon changes into a brown, slimy ooze, as a result of feeding by fungi, yeasts, bacteria, and insects (Figure 6). This surface slime flux may kill injured cambium and bark surface organisms as well as grass growing near the base of the tree. Otherwise, wetwood disease does not appear to be directly harmful to the tree. However, as the internal tissues are infected, the tree may lose some of its stored carbohydrate reserves and have less energy for warding off other diseases or insects or the effects of drought or pruning. Once a tree is infected, the disease does not normally go away.

Wetwood-infected trees have an internal core of wood that is wet but not decayed. These infected branch, trunk, and root tissues also have a high pH. Wetwood-infected wood is resistant to decay by fungi. The extent of wetwood spread in the tree may be limited by tree defenses; however, wetwood can spread into new tissues as new injuries occur. Thus deep injection holes and pruning can expand wetwood infection. Tree workers must take care to avoid pruning live branches on infected trees.

Control. Thus far, no effective preventive or curative measure is known. If the bark is being stained it may be helpful to drain the slime flux away from the branch or trunk so that it drips on the ground. Drilling a hole into the tree and inserting a copper or semi-rigid plastic tube has helped in some cases; however, this results in additional wounding and the threat of expanded wetwood or decay should be considered. Loose dead bark should be carefully cut away so that the area can dry.

American elm tree showing slime flux, evidence of infection with bacterial wetwood. Photo by Mike Schomaker, Colorado State Forest Service, Bugwood.org

Reprinted from "Bacterial Wetwood and Slime Flux of Landscape Trees" By John Hartman in the current edition of the Kentucky Pest News. For the article with associated pictures go to http://www.uky.edu/Ag/kpn/kpn_09/pn_090804.html

Landscape and Nursery - Japanese Maple Scale Observations

Japanese Maple Scale is becoming a bigger problem in this region. The following is an article from the University of Maryland detailing observations on this pest in 2009.

Japanese Maple Scale (JMS) has been in MD for many years with records back to at least 1960. However, in the last 5 or so years the populations of this armored scale have increased to the point where it has become a key pest in nurseries (and landscapes) causing significant economic and aesthetic damage to a wide range of host trees. There are many challenges to monitoring and managing JMS: the life cycle (# of generations, timing of crawler activity) is not clear; wide host range of woody trees and shrubs; and very small size. Therefore, we (Stan Gill, Paula Shrewsbury, our technicians) with the help of growers and scouts have increased our efforts to learn more about JMS biology and management.

Here we provide a quick update on where the JMS populations are in their development this week (based on JMS populations we are monitoring in Frederick and Montgomery Counties MD) to help nursery managers and scouts make better management decisions.

Eggs of JMS from overwintering females began hatching the week of June 8th to start the 1st JMS generation of 2009. Many of you targeted JMS for control around mid-June. This week it appears that about ½ of the 1st generation JMS are immature 2nd instars; the other ½ consists of adult females (no eggs as of yet) and males that are close to emerging as adults (pre-pupal and pupal stages). We will let you know when the 1st generation females lay eggs and those eggs hatch to crawlers which will start the 2nd JMS generation of 2009. This will be the time to apply control measures targeting the 2nd generation crawlers. To our knowledge an application of an IGR (Talus or Distance) with a 0.5-1.0% oil targeting the crawlers should provide the best control. One “fly in the ointment” with JMS is that we have continued to find JMS adult females from the overwintering generation with viable eggs under their covers, although fewer and fewer over the weeks since initial egg hatch in mid-June. What this means is that we have been having continual egg hatch / 1st generation crawler activity since mid-June. It is likely that pesticide applications applied in mid-June may no longer be effective at killing a proportion of these “late emerging 1st generation crawlers”. This is why those of you fighting the battle of JMS should seriously consider a 2nd treatment application when the 2nd generation crawlers become active.

For more information on Japanese maple scale go to: http://ipmnet.umd.edu/09JapaneseMapleScale-UMD.pdf

Information from the current issue of the TPM/IPM Weekly Report for Arborists, Landscape Managers & Nursery Managers from the University of Maryland Cooperative Extension http://www.ipmnet.umd.edu/09Jul31L.pdf

Turf - Causes for Turf Deterioration

Before renovating a turf area, it is critical to assess why the grass declined. The following are potential causes for turf deterioration.

Causes of turf deterioration

The first step in lawn renovation is to correct the primary cause of turf deterioration. Such things as drought, excessive shade, tree root competition, poor drainage, soil compaction, inadequate fertility, acid soils, weed or insect infestation, disease, thatch build-up, improper mowing, poorly-adapted grass species and cultivars, and others may contribute to poor turf. Most of these problems can be corrected by renovation, proper turfgrass selection, and improved maintenance practices.

Shade problems

Shade problems may require removal of some trees, pruning, and planting turfgrass species that are adapted to shaded conditions. Tree roots may need pruning to reduce competition with grasses for water, air, and nutrients.

Poor drainage

Drainage problems can often be corrected by breaking-up compacted soil or through installation of drainage tile. Where surface drainage is insufficient, the site may have to be regraded so that water is removed from the site.

Soil fertility and acidity

Inadequate fertility or acid soils which can limit turf growth can be determined by testing the soil. Soil testing services are available from the Soil Testing Laboratory at the University of Delaware or through private laboratories. Kit for the soil tests are available at a nominal fee from the cooperative extension office in your county. Soil test laboratories will provide recommendations for the amounts of fertilizer and lime that need to be applied to the lawn.

Pests

Pests that cause serious turf damage need to be identified and controlled. If you cannot identify these pests, take fresh samples to your county extension office or another knowledgeable source to have them identified. The most common pest problem causing decline in Delaware turf is grubs (severa species of beetle larvae such as Japanese beetle).

Thatch

Thatch is a tightly intermingled layer of partially decomposed grass stems and roots which develops beneath the actively growing green vegetation and above the soil surface. Thatch decreases the vigor of turfgrasses by restricting the movement of water, fertilizers, and pesticides into soil. Turfgrass roots also grow into the thatch and may become desiccated as the thatch dries. Thatch builds up over a period of years and must dealt with. The best approach to managing thatch is core aeration that brings some soil up into the thatch layer. The soil will have microorganisms in it that can help the thatch to decay. Thatch removal equipment can usually be rented from garden centers or rental outlets however this is a temporary solution usually

Mowing

Mowing on most lawns should be at two inches or above and on a regular basis as long as the grass is growing. How frequently the grass is mowed depends on the growth rate of the grass. No more than one third of the total leaf surface should be removed at a given mowing. Thus, if the turf is cut at two inches, it should be mowed when it reaches a height no greater than three inches. Clippings do not need to be removed provided the lawn is mowed on a regular basis. All mowing equipment needs to be sharpened and adjusted periodically.

Species and management

Unadapted species and improper management are perhaps the most common causes of turfgrass deterioration. Species and management must be adapted to the conditions present at the site. Other problems include the use of inferior turfgrass cultivars and poor quality seed. Once the reasons for lawn deterioration are recognized and steps are taken to correct the problems, the renovation program can begin. The following three programs are designed to fit most renovation situations. Some operations may need to be altered or omitted depending on the individual situation.

Information adapted from a fact sheet from Penn State University http://cropsoil.psu.edu/Extension/Turf/pdf/ec412.pdf

Landscape - Pine Needle Scale

I recently identified pine needle scale on white pine. The following is information about the life cycle of this common pest.

The pine needle scale, Chionaspis pinifoliae (Fitch), is probably the most common armored scale found on conifers in the United States and Canada. The white, oystershell shaped scales can completely cover needles, causing plant discoloration to needle and branch death.

This scale settles on the needles of its host and forms white, oyster shell-shaped wax covers. These covers or armor are about 1/16 to 1/8- inch long when the scales are fully grown and there is a yellowish spot, the exuvim, on the small end. The male scales are usually smaller and more slender. This scale overwinters as deep reddish colored eggs protected under the female's old armor. The eggs hatch in mid-May into tiny, flat nymphs called crawlers. These crawlers creep to new places on the tree in order to find suitable needles on which to feed. These clumsy crawlers often fall from the trees and may be blown onto nearby trees. Once settled on a suitable needle, the crawler inserts its hair-like mouthparts, and begins to form the new armor. After a couple of weeks, the nymph molts under the armor and continues to increase in size for about three weeks. By this time male scales are smaller and more slender than the females. The males molt into a pre-pupa for a week before emerging as winged adults. The females, however, molt into wingless nymph-like adults. After mating, the females continue to grow for a couple of weeks before laying eggs under the armor. Females produce an average of 40 eggs.
Two generations of this scale occur. The overwintering eggs hatch in mid-May and the summer produced eggs hatch in late July. Unfortunately, the eggs may hatch over a period of two to three weeks.

Information from the Ohio State University http://ohioline.osu.edu/hyg-fact/2000/2553.html

Greenhouse and Nursery - Wet Weather Means Diseases in Mums

The following is excellent information on common diseases of mums. With the wet weather, growers should be watching for these diseases.

The primary diseases of garden mums are bacterial leaf spot, Fusarium wilt, Pythium root rot, and Rhizoctonia stem rot and foliar blight. Bacterial leaf spot is caused by Pseudomonas cichorii which is often more prevalent following periods of heavy summer rains.

Bacterial leaf spot development is favored by moisture, high humidity, high temperatures, and/or use of susceptible cultivars. Symptoms include dark-brown to black irregularly-shaped spots that can cover half the leaf. Small spots expand to large lesions under wet conditions. The disease typically begins with the lower leaves and will spread upward. For control, avoid growing cultivars that have been destroyed by bacterial leaf spot in the past: cultivars vary immensely in their susceptibility. Copper sprays may reduce disease spread, but use overhead irrigation as little as possible, and irrigate early in the day so that foliage dries off as quickly as possible.

Fusarium wilt is caused by Fusarium oxysporum f. sp. chrysanthemi. It may be received with mum cuttings or picked up by the roots of the growing crop if the area has been contaminated in previous years. Some cultivars may show no symptoms, others may exhibit yellowing or stunting, and some will be severely wilted and die. To minimize Fusarium wilt losses, avoid growing cultivars that have succumbed to the disease in your experience. Drenches with thiophanate-methyl may be helpful. A pH above 6.0 and nitrate rather than ammonium forms of nitrogen will reduce Fusarium wilt losses, but may create other cultural problems.

Pythium aphanidermatum is the species of Pythium most commonly causing root rot losses to mums in recent years. The pathogen thrives in hot, summer weather. Avoid puddling around containers, deep planting or overwatering. Provide even moisture and avoid high EC values: any root stress may open the plant up to Pythium attack. For control (New York recommendations), utilize etridiazole-containing fungicides (Truban, Terrazole, Banrol) at a monthly interval. An occasional treatment with mefenoxam (e.g. SubdueMAXX) is advisable in rotation with the etridiazole, but beware of using mefenoxam exclusively because of widespread fungicide resistance issues with that active ingredient. 5

Rhizoctonia solani is occasionally a problem either as a stem rot or a foliar disease agent. Affected plants will show wilting or tan-to-brown lesions on leaves, depending on the nature of the Rhizoctonia attack. Practice careful sanitation to keep Rhizoctonia under control: do not allow contact between the mum crop and field soil, which is a source of inoculum. A number of fungicides are effective against Rhizoctonia, including thiophanate-methyl (in 3336, 6672, Banrot), strobilurins (e.g. Heritage, Insignia, Compass) and PCNB (Terraclor).

Information from 'Optimizing Garden Mum Production" by Dr. Mark Bridgen, Professor,
Cornell University http://www.canadiangreenhouseconference.com/talks/2008/2008-TK-Bridgen.pdf

Other diseases we see on garden mums in Delaware are Septoria leaf spot which can be controlled with protectant fungicide sprays if started early and foliar nematodes which can be very difficult to control if present and requires the use of systemic insecticides. Gordon Johnson, Extension Horticulture Agent, UD, Kent County

Landscape - Dogwood Sawflies

Sawflies have larvae that look somewhat like caterpillars but are not, they are related to wasps. One sawfly that is active in Delaware is the dogwood sawfly. The following is more information.

Dogwood Sawflies.

Wasp-like adults emerge sometime in May through July and oviposit eggs onto the underside of leaves. Dogwood sawflies are serious pests of Cornus species, but seem to prefer Cornus racemosa and Cornus sericea. Larvae are active 1041-1914 GDD or when Aesculus parviflora is in bloom. First instars are difficult to spot because they are transparent yellow, but later instars are covered with a white chalky powder. Larvae feed gregariously and skeletonize leaves as early instars, but eventually consume entire leaves except for tough mid-veins. The last molt changes the larvae to a yellowish colored insect with a shiny black head and spots. Mature larvae overwinter in decaying wood. Parasitoids will attack dogwood sawflies and cultural control consists of hand-picking larvae from leaves. Chemical control options include horticultural oil, insecticidal soap, spinosad, acephate, carbaryl, imidacloprid, or one of the pyrethroids such as cyfluthrin or deltamethrin.

Dogwood sawfly larvae feeding. Photo by Jerry A. Payne, USDA Agricultural Research Service, Bugwood.org

Information from Brian Kunkel, Ornamental IPM Specialist, UD

Nursery and Greenhouse - Controlling Phytophthora

Phytophthora root rot can be a major problem in nurseries and greenhouses. The following are some recommendations for contolling this disease from Rutgers University.

Phytophthora can be very difficult to eradicate once established. Successful disease management, therefore, requires an approach that utilizes preventive cultural practices. To manage this disease:

• Use only pathogen-free stock. Purchase only healthy, vigorous stock, and inspect these plants carefully for signs of disease. Imported stock should be segregated in the nursery for several months to be sure the plants are free of disease. Propagate only from cuttings taken from disease-free mother plants.

• Plant only in pathogen-free soil or potting mix. Since Phytophthora root and crown rot is easily spread through the movement of infested soil, all potting mix components should be steam-pasteurized before use. Once pasteurized, mix components should not come into contact with fresh soil or plant debris. In the propagation house, containers should be new or surface-sterilized before use. All propagation tools, benches, and beds should also be surface-sterilized. In field sites with a history of this disease, an appropriate chemical fumigant should be applied before planting.

• Select well-drained potting mixes and field sites. Phytophthora root and crown rot tends to be more severe in container plants than in the field because over-watering is a frequent problem and mix temperatures tend to be higher. The disease can also be a problem when soil, peat moss, or sawdust is used as the sole component of the container mix. A mix high in sawdust is more conducive to disease development because drainage is poorer. A good potting medium should generally contain 20 to 25% air-filled pore space. When used as a potting mix amendment, composted hardwood bark releases inhibitors that suppress disease development.

• To prevent the dispersal of spores of P. cinnamomi through splashing in the nursery, place container plants on a well-drained base, such as three to four inches of gravel. Container beds should be graded to allow water to drain away from the pots and prevent puddling. In the field, select planting sites that are most appropriate for vigorous growth.

• Maintain plant vigor. Maintain proper levels of soil nutrients, moisture, and soil pH. Avoid over-watering and cultural practices that promote overly succulent growth, such as heavy fertilization, over-crowding, and low light. Succulent plants and those under stress are more susceptible to disease.

• Utilize disease resistant plants and cultivars when possible. Many well-known azalea and rhododendron hybrids are very susceptible to this disease. Under severe environmental stress, however, even tolerant cultivars may succumb to this disease.

• Apply an appropriate fungicide when necessary. Fungicides such as Banrot, dimethomorph, etridiazole, fenamidone (greenhouse only), fosetyl- Al (drench, foliar spray, soil treatment), Hurricane (enclosed structures only), mefenoxam, phosphite (spray, drench, soil pre-treatment), propamocarb- HCl, or SoilGard are useful when applied as a preventively as per manufacturer's recommendations. Once plants become infected, fungicides may arrest further infection but do not kill the fungi within infected roots and soil. Although fungicides are useful for disease control, they cannot replace good cultural practices.

Information from Ann B. Gould, Ph.D., Specialist in Plant Pathology, Rutgers University http://njaes.rutgers.edu/pubs/plantandpestadvisory/2008/ln0807.pdf

Landscape - Fall Webworms

It is the time of the year to see fall webworms on many trees and shrubs. The following is more information.

Fall webworms feed on over 85 species of trees including, walnut, hickory, fruit trees, maples, cherry, and sweetgum. There are two generations in the mid-Atlantic area. Fall webworm overwinter as pupa in leaf litter, old nests, or in crevices found in bark, and emerge sometime in mid to late June. Females lay eggs on the underside of leaves and egg hatch occurs between 802 and 1517 [1105 peak hatch] GDD. The larvae are pale yellow to pale green with black spots along the back. Caterpillars are covered with long white to yellowish colored hairs. The second generation of fall webworm is seen later in the summer with peak egg hatch at 2723 GDD. Physically remove the nests and tear open nests with pruners, or a stream of water from a high pressure hose. Natural enemies such as birds, predatory insects and parasitoids will take advantage of damaged nests. Chemical control if necessary may include B.t., insecticidal soap, spinosad, tebufenozide, diflubenzuron, or a pyrethroid.

Fall Webworm. Photo from the Pennsylvania Department of Conservation and Natural Resources - Forestry Archive, Bugwood.org

Information from Brian Kunkel, Ornamental IPM Specialist, UD

Turf - Brown Patch Now Appearing

Brown patch season has arrived in turf across Delaware. The following is more information.

Brown Patch disease is active now after recent rains and high night humidity. Turf-type tall fescue and others turf species are susceptible when the weather turns hazy, hot and humid and night temperatures stay in the 70's. This disease, caused by the fungus Rhizoctonia solani, has been present for the past week on landscape turf and golf courses. To reduce the incidence and severity of brown patch for golf courses and other highly managed turf, avoid summer avoid large applications of quick release nitrogen sources (e.g., not more than ¼ lb actual N/1000 sq. ft) during hot weather, irrigate between midnight and 8 a.m. to minimize the leaf wetness period, and spray turf now with Armada, Banner (preventive only), Chipco 26GT, chlorothalonil, Compass, ConSyst, Curalan, Disarm, Eagle, Endorse, Headway, Heritage, Insignia, mancozeb, Medallion, Prostar, Spectro, Tartan, thiophanate-methyl or Trinity per manufacturer's recommendations.

Information from Bob Mulrooney, Extension Plant Pathologist, UD.