Turf - Brown Patch Season

Summer means brown patch disease season in turfgrasses. The following is more information.

Brown patch disease will be coming active in Delaware soon, especially in tall fescue. Warm, humid weather will promote brown patch activity on cool- season turfgrasses. Perennial ryegrass is probably the most susceptible host; creeping bentgrass and tall fescue are both relatively susceptible. Sometimes we see brown patch on Kentucky bluegrass, as well.

On all grasses, affected patches are often somewhat circular and can range from several inches to two or more feet in size. On tall fescue and Kentucky bluegrass, leaves exhibit tan, irregular lesions with a thin, brown border. On creeping bentgrass and perennial ryegrass, a ring of olive- green leaf blades appears on the outside margin of the patch; these blighted leaf blades dry to a tan color. On humid mornings, the mycelium of the fungus often appears as a sparse, very light tan webbing in the lower canopy. This can be best seen with a hand lens. In some situations on perennial ryegrass, the mycelium can be quite dense, cottony, and fluffy, and grow all over the leaf blades. In this condition, it can look quite a bit like Pythium cottony blight. Since different fungicides are used against Pythium cottony blight and Rhizoctonia brown patch, knowing the identity of the disease can be quite important from a management standpoint. Laboratory diagnosis is the best option if a case of perennial ryegrass has dense mycelium that looks like Pythium blight.

Management: During the next 8-10 weeks or so, be careful with postemergence herbicides, some of which have been shown to increase brown patch activity on cool-season turfgrasses.

Tall fescue. Generally brown patch can be managed through cultural means in established tall fescue lawns. However, recent seedings of tall fescue often can suffer severe outbreaks of the disease during humid weather in summer months. These should be monitored carefully and treated with fungicide if necessary. Once these swards make it through their first summer and are well-established, they often do not need fungicide treatment to maintain sward density, although fungicides do improve overall greenness during summer. Be aware that products containing chlorothalonil and iprodione are no longer labeled for use on home lawns.

Kentucky bluegrass. Although brown patch may be active in adapted varieties of Kentucky bluegrass, brown patch rarely develops aggressively enough on this host to justify fungicide treatment.

Perennial ryegrass and creeping bentgrass. High- maintenance perennial ryegrass and creeping bentgrass swards should have preventive fungicide applications on at this point, and putting greens should continue to receive preventive applications for brown patch control through August (and possibly later, depending on weather).

There is a wide selection of fungicides with very good activity for brown patch control. See the Extension publication PPA-1, Chemical Control of Turfgrass Diseases (http://www.ca.uky.edu/agc/pubs/ppa/ppa1/ppa1.pdf) for options.

Adapted from "Brown Patch Activity" By Paul Vincelli in the current edition of the Kentucky Pest News http://www.uky.edu/Ag/kpn/kpn_09/pn_090630.html

Turf - Controlling Crabgrass Breaks

The following is general information on controlling crabgrass breaks in turf.

With the heavy rains and cool weather conditions this spring I’m expecting that a significant number of preemergence herbicide applications will fail. Above average rainfall will result in an increased dissipation of preemergence herbicide out of the crabgrass germination zone while the cool temperatures are prolonging the crabgrass germination cycle. As always, maintaining a dense and healthy turfgrass stand throughout the summer is our first and best line of defense to prevent preemergence crabgrass herbicide failures. However, if summer stresses which thin and weaken the turfgrass stand occur; postemergence herbicides may need to be utilized to control crabgrass that germinates later in the season.

Both Acclaim Extra and Drive herbicides can be used to control crabgrass breaks. However, crabgrass cannot be too large (ideally less than 2 tillers, but no more than 4 tillers). Both herbicides are most effective when applied to young actively growing crabgrass in good soil moisture conditions. Applying either herbicide to sites under drought and/or heat stress may result in reduced control of crabgrass and other summer annual grasses as well as increased potential for turfgrass injury. Weed control with both herbicides is most effective when applied with flat fan nozzles producing a fine spray droplet. I do not recommended the use of flood jets with either herbicide. Both herbicides may be applied in combination with residual preemergence herbicides. However, applying residual herbicides late in the season may interfere with overseeding operations in late summer/fall.

Information adapted from an article from Dr. Steve Hart, Extension Weed Science Specialist, Rutgers University.

Turf - Drive for Postemergence Crabgrass Control

Crabgrass breaks are occurring in landscapes this year due to the previous wet weather. The following is information on using quinclorac (Drive) herbicide for postemergence crabgrass control.

Drive Herbicide

Drive herbicide (quinclorac) is safe on Kentucky bluegrass, perennial ryegrass and tall fescue. Consult the label carefully for use on bentgrasses and fine fescue. Drive can be effective on 2-4 tillered crabgrass but for the most consistent control Drive should be applied to crabgrass prior to two tillers. Drive is also highly active on large multi-tillered crabgrass but only when it has entered its reproductive phase (visable seedheads). Drive will not control goosegrass. Drive is tank-mix compatible with broadleaf weed herbicides. For optimum activity Drive must be applied with methylated seed oil (MSO). Two formulations are available: Drive 75 DF and a new liquid formulation Drive XLR8 1.5 L. In some studies we have observed more consistent crabgrass control with Drive XLR8 compared to Drive 75 DF.

Combination Products: A number of combination products are currently being marketed such as Q4, Quincept, and Onetime, which contain Drive in combination with broadleaf weed herbicides or in the case of Q4 also contain sulfentrazone for suppression of yellow nutsedge. Consult labels carefully to determine if a spray adjuvant is recommended. Also determine the use rate of quinclorac (the active ingredient in Drive) you will be applying. Applying quinclorac at less than 0.75 lbs ai/A and/or without a spray adjuvant such as methylated seed oil may reduce the consistency of crabgrass control especially if the growth stage has exceeded one-tiller.

Information from Dr. Stephen E. Hart, Associate Extension Specialist, Weed Science, Rutgers University

Turf - Evaluating Turf for Complete Renovation

Problem grass weeds in cool season turf often cannot be controlled except by complete renovation. The following is an article on the subject.

Assessing Turf for Complete Renovation.

Mid-summer is the time to assess turf areas for the need to do a complete renovation. In particular, where problem perennial grasses such as wiregrass, nimblewill, zoysiagrass, bentgrass, orchardgrass, or coarse type tall fescues have become established in desired cool season turf, a complete renovation needs to start in summer with herbicide applications to kill them. Other reasons for a complete renovation include heavy traffic, disease pressure, insect damage, or general loss of stand due to other stresses.

If you have heavy infestations of problem perennial grasses, one option is to apply 2 applications of glyphosate herbicide, three weeks apart. You need to allow sufficient time for any remaining weeds to die after the second application before seeding in late summer; therefore, the first application should go on in late July through early August. For heavy infestations of Zoysiagrass or wiregrass, 3 applications may be needed starting in mid-July. For orchardgrass, bentgrass, coarse tall fescue, or other undesired cool season perennial grasses, turf areas should be irrigated to encourage growth prior to applying glyphosate as it will not work on drought stressed or heat dormant plants. For troublesome perennial weed patches, Basamid soil fumigant may be another option. Basamid is applied as a granule and is watered in. It performs best if it is tilled in or is tarped with plastic. Research has shown good control of nimblewill, bermudagrass, and creeping bentgrass by fumigation with Basamid.

Gordon Johnson, Extension Horticulture Agent, UD, Kent County

Turf - Acclaim For Crabgrass Control

One of the materials available for postemergence crabgrass control in turf is Acclaim Extra. The following is more information.

Acclaim Extra: The recommended use rate of Acclaim Extra is highly dependent on turf grass species and growth stage of crabgrass. Consult the label carefully, especially for use on bentgrasses. Although the label states that 28 oz/A may be used on well established Kentucky bluegrass, I generally do not recommend exceeding 20 oz/A. Tall and fine fescue as well as perennial ryegrass are very tolerant to Acclaim Extra. At 20 oz/A Acclaim Extra is effective on crabgrass up to 2 tillers. However, under favorable environmental conditions, I have observed that this rate can control crabgrass up to 3-4 tillers. Tank-mixing or applying Acclaim Extra prior to or following a broadleaf weed herbicide application (especially herbicides containing 2,4-D and/or MCPP) may reduce weed control. Although the formulation contains a built in spray adjuvant system, depending on application equipment the addition of non-ionic surfactant (NIS) may be recommended.

Information from Dr. Stephen E. Hart, Associate Extension Specialist, Rutgers University.

Landscape - Juniper Scales

The following is information on Juniper scales that have been hatching in the landscape.

Juniper Scale

This imported armored scale insect is found on the foliage and twigs of juniper (occasionally arborvitae). The female covers are circular and white (1/16 inch in diameter); the male covers are white and elongated and are even smaller in size. With light infestations there is often no apparent symptoms. Significant populations of 10 or more scales per ½ inch of twig can result in yellowed foliage and needle drop. Dieback can occur with high populations. Scales usually build up first on the south side of shrubs or on the side against buildings. Adult females over-winter on the foliage and there is only one generation each year. Crawlers start hatching by mid-June and can continue well into July.

Controls may not be required if many beneficials are present (monitor for parasitoid exit holes in covers and for dustywings and ladybeetles). Dormant oil sprays can be used and summer oils or insecticidal soaps can be targeted against the crawlers. A late summer systemic insecticide such as acephate (Orthene) can be applied if the crawler stage is missed.

Juniper scale. Photo by United States National Collection of Scale Insects Photographs Archive, USDA Agricultural Research Service, Bugwood.org.

Information from Steven K. Rettke, Ornamental IPM Program Associate, Rutgers University in the June 11, 2009 edition of the Plant and Pest Advisory, Landscape, Nursery and Turf Edition from Rutgers University http://njaes.rutgers.edu/pubs/plantandpestadvisory/2009/ln061109.pdf

Landscape - Closeup of Spittebugs

We have recently had an influx of spittlebugs in the landscape, expecially on Leyland Cypress. They are mostly a nuisance pest and rarely damage plants enough to warrant control. The following are some closeup pictures of the spittle they create and what these insects look like when uncovered.




Photos by Tracy Wootten, Extension Horticulture Agent, UD, Sussex County

Landscape - Honeydew Means Aphids

Honeydew presence means aphid infestations in landscape plants. The following is more information.

You or your clients may notice honeydew on cars and sidewalks. This is a sign of aphid infestations in nearby trees or shrubs. There are a number of aphid species that feed in landscape trees and go largely unnoticed until honeydew rains down on surfaces where it is not wanted. Many tree species and large shrubs can be attacked by aphids. Fortunately, aphids are often “cleaned up” by ladybugs and other natural enemies and do not cause permanent harm to the trees. However, on nursery stock, landscape specimen plants, or trees that shade a client’s fancy car, control may be needed. Luckily there are a number of products such as imidacloprid, Tristar, Safari and others that can provide long term aphid suppression and can often be applied in foliar or drench applications.

Adapted from an article in the North Carolina Pest News http://ipm.ncsu.edu/current_ipm/09PestNews/09News7/pestnews.pdf

Turf - Grub Control

The following is a good article on grub control in turf from Rutgers University.

Soon they will be flying again, the adults of those pesky white grubs, like oriental beetle, Japanese beetle, masked chafers, Asiatic garden beetle, European chafer, and green June beetle. Adult oriental beetles typically peak in abundance from late-June into early July, followed by Japanese beetles about mid-July. Peak adult activity means peak egg-laying which is followed 2-3 weeks later by peak hatching off the eggs.

The young first stage larvae are the stage that is the most susceptible to insecticides, and numbers of this stage peak from mid-July to early August. If an applicator chooses to preventively treat turf for white grubs, the ideal time to do an application would be somewhat earlier than the time of peak first larval stage density to allow the insecticidal active ingredient to reach peak concentration in the target zone, i.e., the thatch and top 1-2 inches of the soil. How much earlier depends on how fast the active ingredient will move through the thatch. Generally, the more water soluble an active ingredient is, the faster it will move downwards into the soil with rain and irrigation water.

However, the application window of most of the newer white grub insecticides is rather wide and many of them can be applied from May into August with little differences in control rates. Reasons for these wide windows are that (1) the active ingredient has a long half-life in the soil allowing earlier applications, (2) the second larval stage of the white grubs is generally still very susceptible to the active ingredient allowing later applications, and/or (3) the recommended application rates are high enough to compensate for 1-3 months of slow active ingredient breakdown in the soil or the lower susceptibility of the larger white grubs.

Imidacloprid (Merit) and thiamethoxam (Meridian) seem to be very effective when applied from May through August, clothianidin (Arena) even from May into September, halofenozide (Mach2) from June through August, and chlorantraniliprole (Acelepryn) from April at least into mid-August.

An interesting new finding is that chlorantraniliprole (Acelepryn) actually tends to be more effective when applied earlier. Due to its very low water solubility (> 5 ppm) chlorantraniliprole takes around 50 days to reach peak concentration in the thatch and 100 days to reach peak concentration in the soil. However, chlorantraniliprole clearly is effective enough to compensate for this slow movement. Averaged over dozens of research trials for each application timing, chlorantraniliprole at 0.1 lb active ingredient per acre applied in April, May, June, July, and August has provided 96%, 94%, 91%, 88%, and 79% control, respectively, of all the major white grub species. However, even the 79% control in August is at least as good as what one can expect with an application of trichlorfon (Dylox) and certainly good enough to suppress white grub damage.

As always, keep in mind that repeated application of the same insecticide class year after year could lead to insecticide resistance and/or enhanced microbial degradation of the compound. Enhanced microbial degradation would be particularly problematic if the compound is applied several weeks to months before the presence of the target (i.e., before July). Therefore regularly rotate insecticides from different insecticide classes. Earlier applications are also more likely to interfere with naturally occurring predators and parasites of white grubs and other turfgrass insect pests. Applications before July or even June should therefore be reserved for cases where there is some additional benefit such as suppression of other insect pests with damage potential.

Reprinted from "Timing of White Grub Treatments in Turfgrass" by Albrecht M. Koppenhöfer, Ph.D., Specialist in Turfgrass Entomology in the June 11, 2009 edition of the Plant and Pest Advisory, Landscape, Nursery, and Turf Edition from Rutgers University http://njaes.rutgers.edu/pubs/plantandpestadvisory/2009/ln061109.pdf

Landscape and Turf - Low pH and Poor Plant Performance

The following is information on low pH and poor plant performance in the landscape.

Over the years, I have observed plant growth problems in the landscape associated with low pH. In most of these cases, the soil in the poor growth area was quite acidic, pH in the 5.2 or lower. Available soil nutrient levels were often adequate. However, the plant tissue analysis in these samples showed low phosphorus and magnesium levels and in some cases elevated levels of iron and aluminum. Without soil pH information, one may have concluded that the plant growth problem was due to inadequate available phosphorus or magnesium in the soil.

The remedy is applied needed lime to those individual spots, not applying phosphorus or magnesium. When the soil pH is below 5.2, availability of aluminum, iron and manganese increases significantly. This results in increased uptake of these three elements. Aluminum and manganese begin to accumulate to the point of becoming slightly toxic and reducing root growth. Reduced root growth results in greatly reduced uptake of phosphorus, which is relatively immobile in the soil. Uptake of other nutrients will also be reduced, resulting in poor growth. Magnesium availability decreases as the soil pH decreases, especially below 5.2, resulting in low levels in the plant. Also, under acidic soil conditions microbial activity is reduced, resulting in reduced mineralization of nitrogen and sulfur from soil organic matter and organic soil ammendment.

It is not unusual to see acid spots in landscapes even with overall soil pHs in the 5.8 to 6.5 range. These spots can vary greatly in size. Theses spots are usually found in newly developed properties where subsoil was exposed or inadequate topsoil replaced, in the sandiest areas, or in turf were excessive N fertilizer is being used. Subsoil is naturally acid in DE and exposed subsoil or inadequate replacement of topsoil will result in acid spots. Excessive applications of N fertilizers results in areas becoming acidic more quickly. In very sandy spots, excess leaching of basic cations results pH dropping rapidly. When diagnosing plant growth problems, be sure to check soil pH first and look at the plant roots.

Adapted from "Soil pH, the source of plant growth problems" from Darryl Warncke, Crop and Soil Sciences, Michigan State University on the MSU Field Crop Advisory Alert web site.

Landscape and Nursery - New Resource for Perennial Diseases

The following is information on a new resource for perennial diseases. Landscapers and nurserymen should consider adding this reference to their libraries.

An excellent new reference for plant enthusiasts was just published by APS Press, “Diseases of Herbaceous Perennials”. It will be the 'bible' of perennial disease identification for some time. It is full of excellent full color photos of your favorite diseases comparable to other coffee table books. Horticultural information and pictures of healthy plants are provided by Dr. Alan Armitage, noted perennial plantsman. Ordering information can be found at
http://www.shopapspress.org/hepepl.htm. Price is $79.00.

Landscape - Powdery Mildew on Dogwood

It is powdery mildew season for dogwoods in the landscape. The following are some control recommendations.

Disease management. Powdery mildew can be confronted by using cultural practices, planting resistant dogwoods, and by using fungicides.

Avoid cultural practices that stimulate succulent growth and encourage powdery mildew. These include applying nitrogen fertilizer, pruning heavily, and irrigating excessively.

Use good cultural practices such as mulching over the root system, pruning out dead branches, and providing good air movement and light penetration by judicious pruning of nearby vegetation.

Plant dogwood species and cultivars resistant to powdery mildew.

Susceptible: All Cornus florida, seedling wild types (but individuals vary in susceptibility) and most C. florida cultivars.

Intermediate susceptibility: C. florida ‘Cherokee Brave’ and cultivars of the C. florida x C. kousa hybrids.

Resistant: Four powdery mildew resistant C. florida cultivars have been developed by the Tennessee Agricultural Experiment Station and are available in the nursery trade. They include ‘Jean’s Appalachian Snow’, ‘Karen’s Appalachian Blush’, ‘Kay’s Appalachian Mist’, and ‘Appalachian Joy’. Also resistant: Cultivars of C. kousa, oriental dogwood.

Immune: Cornelian cherry dogwood, C. mas.

If fungicides are to be used, determine which trees in the landscape are most susceptible so that applications are not made unnecessarily. Those trees most at risk for powdery mildew disease then can be considered for preventive fungicide applications. Most fungicides are capable of stopping the progress of powdery mildew infections fairly quickly, but none will restore already discolored or damaged leaf tissues. Good control can be obtained with as few as four fungicide applications made three weeks apart. Begin applications by early June. Delayed application can still help protect some leaves.

Effective fungicides include:
azoxystrobin (Heritage)
fenarimol (Rubigan)
myclobutanil (Eagle, Immunox, Procoz Hoist)
propiconazol (Banner Maxx, Procon-Z, Procoz Fathom, Propensity)
thiophanate-methyl (Cleary’s 3336)
triadimefon (Bayleton, Strike)

Powdery mildew fungicides requiring more frequent applications to be effective include:
neem oil (Triact)
potassium bicarbonate (Bonide Remedy, FirstStep, Kaligreen, Milstop)
paraffinic oil (Sunspray UF Oil)

When using fungicides for powdery mildew management, be sure that dogwoods are listed on the label and carefully follow all label directions.

Information from an article by John Hartman in the current edition of the Kentucky Pest News http://www.uky.edu/Ag/kpn/kpn_09/pn_090623.html

Landscape - Downy Mildews

The wet weather has brought out some diseases we normally do not see in the landscape. The following is information on downy mildews in landscape plants.

Downy mildews that are rather uncommon in the area have been favored by the continued rainy, cool weather. Downy mildew of rose occurs worldwide but is rare here. Infected leaves develop purplish red to dark brown irregular spots and leaflets may turn yellow with ½-inch islands of normal green tissue interspersed. Leaf loss can be severe and symptoms may resemble pesticide toxicity burns. Sanitation is important, since the fungus overwinters in infected leaves. Rake and dispose of fallen leaves, stems and flowers. The other downy mildews have been diagnosed on sunflower and black-eyed Susan, both infected by Plasmopara halstedii. Usually this downy mildew appears in the fall with cool and wet conditions, but not this year. It causes yellow to dark blotchy areas on the upper leaf surfaces and grayish white fuzzy growth on leaf undersides. It can infect most species of Rudbeckia especially 'Goldstrum'. Preventative fungicides can help suppress or control downy mildew. A return to normal weather this week will slow disease development.

Downy mildew on rose. Photo from the Oregon State University Online Guide to Plant Disease Control.

Information from Bob Mulrooney, Extension Plant Pathologist, UD

Greenhouse and Nursery - Flowering Cabbage and Kale Production

Flowering cabbage and kale should be started in mid summer for fall sales. The following is more information on growing flowering kale from the University of Maryland.

Flowering Cabbage and Kale

The flowering kales were very poplar back in the 1990s but have somewhat died-down in popularity since then. Keep in mind this is an 11 week crop so for late fall don’t start your plants until mid- July. The color really comes on when it starts getting cold at night. The seed for most commercial cultivars was developed by Sakata Seed America or Takii America. The seed is available through many different wholesale seed companies.

The shape of the leaf determines whether it is called flowering cabbage and or flowering kale. Cultivars with smooth leaf margins constitute the flowering cabbage group while those with divided or "fringed" leaf margins are considered flowering kale. Within the kale group there are two types: the most common are the "fringed leaved cultivars" which have finely ruffled leaf margins and a smaller number which are called "feather leaved cultivars" have leaves that are finely serrated and deeply notched. A grower should select depending on growth habit and coloration that your customers want.

In each series there is normally a white, pink, and red cultivar.

Flowering cabbage cultivars: Tokyo series, Osaka series, Pigeon (red, pink and white) and Color-up series

Fringe-leaved cultivars – Sparrow series, Chidori series and Kamone series (reds and whites), and Naygoya series

Feather-leaved cultivars – ‘Coral Queen’, ‘Coral Prince’, ‘Red Peacock’, and ‘White Peacock’

Culture: The tough part is that growing ornamental cabbage and kale in summer in Maryland can be challenging if the temperatures are high. Cabbage and kale grow best in cool weather (55º to 60º F) nights. Since outdoor temperatures frequently exceed this range during the summer, select a site which has good air circulation and is "relatively" cool.

With high temperatures in the summer there will be excessive stem elongation due to high temperatures. To prevent stem elongation make a 1500 to 3000 ppm B-Nine application when the plants have developed true leaves and before stem elongation occurs. Several applications (it might be as often as once a week) at the same rate may be made during July and August as needed. Do not apply B-Nine if the crop is going to be marketed as an edible crop. Plant

Nutrition: Maintain the substrate pH levels between 5.8 and 6.5. Many growers have used controlled release fertilizers with cabbage and kale with good success. Begin fertilizing at the rate of 50 to 100 pm N and K after seedlings emerge. Once transplanted, fertilize at the rate of 150 to 250 ppm N and K with periodic applications of a complete fertilizer such as 20-10-20. Make sure you keep the fertility and mist levels correct or the plants suffer. Lack of nitrogen will result in the plants turning yellow and losing lower leaves. Maintain fertilization until night temperatures drop and coloration begins which is October in Maryland. In October reduce fertilization to 50 ppm N and K. Excess nitrogent during this period will prevent good coloration.

Reprinted from the June 26, 2009 edition of the Greenhouse TPM/IPM Bi-Weekly Report from the University of Maryland Cooperative Extension, Central Maryland Research and Education Center.

Landscape and Turf - Japanese Beetles

Japanese beetles are emerging across the state. The following is more information.

Japanese beetles are emerging across the state. Adult activity typically occurs between 1094-2410 GDD (base 50). They are highly mobile and feed on over 300 different types of broad-leaved plants. Last year JB adult populations declined in some locations with drier weather in July. Leaves are skeletonized by beetles feeding in between leaf veins. Preferred plants include roses, cannas, flowering crabapple, lindens, Norway and Japanese maples, and elms.

Many natural enemies attack JB life stages such as: assassin bugs, parasitoids, ants, ground beetles, rove beetles, birds, skunks, and raccoons. Cultural control includes hand removal, removing beetle-damaged leaves, or shaking beetles into buckets of soapy water.

Control adults with insecticides including Orthene, Sevin, or one of the pyrethroids (e.g., cyfluthrin, deltamethrin, etc.). Apply insecticides every 1-2 weeks when adult activity is high. Neem based products typically deter feeding for 3-4 days, although some report longer activity. Last year, we reported wettable powder formulations of some pyrethroids (pyrethrins) may be more repellent than EC formulations. Thorough coverage is required. Insecticidal soaps, plant extracts, and companion plantings are generally ineffective. Since adult beetles are mobile, control of white grubs or adult JB does not ensure control of the other life stages. Treat for white grubs using preventive products such as Merit or Mach 2 in mid-June to mid-July. Acelepryn is a new product with a different mode of action than Merit and may be applied as early as May for effective grub control.

Information from Brian Kunkel, Ornamental IPM Specialist, UD.

Landscape - Two Spotted Spider Mites

As landscapes dry out and hot weather sets in, watch for two-spotted spider mites. The following is more information.

The twospotted spider mite, Tetranychus urticae, is an important pest of ornamental and food crops. They feed on over 100 species of plants by sucking the fluid out of cells in leaves and needles. This “stippling” damage can rapidly cause entire plants to take on a bronzed appearance. It is important to scout for twospotted spider mites now because they reproduce most rapidly in hot dry weather. Under these conditions they can mature from egg to reproducing adult in 5 days! Look on the underside of leaves on susceptible hosts or beat foliage on a white piece of paper to scout for spider mites. If you notice mites or their damage a range of control options are available, the best of which are several new miticides that provide long residuals and efficacy against all mite life stages.

CLICK ON TABLE FOR A LARGER VERSION OF MITE CONTROL RECOMMENDATIONS


Information from North Carolina State University:
http://ipm.ncsu.edu/current_ipm/09PestNews/09News8/pestnews.pdf
http://www.ces.ncsu.edu/depts/ent/notes/O&T/flowers/note25/note25.html

Landscape - Honeysuckle Control

Japanese honeysuckle is a common invasive weed in Delaware. The following are some control recommendations.

Japanese Honeysuckle, Lonicera japonica, is in flower across Delaware. Leaves are mostly oval to somewhat lobed, opposite, in pairs. Honeysuckle often remains evergreen through the winter. Flowers are tube shaped, white to pink, turning yellow with age and occur in pairs along the stem at leaf axils. They have a distinctive fragrance. This invasive woody vine is common along wood edges, ditch banks, roadsides, fence lines, low maintenance areas, and right of ways. It was introduced in the early 1900’s from the Far East. It is an aggressive climber and can smother desired shrubs and trees and cover fences or posts.

Control small patches by hand digging. Mowing repeatedly is partially effective on large areas. Mow twice, one in July, again in September and repeat each year. In areas where it is climbing vegetation,cut at the base and remove vines. Apply a herbicide to cut stems. Use a 50% glyphosate herbicide or 25% triclopyr herbicide solution (based on formulated products such as Roundup or Garlon). Foliar applications of a 1-5 to 2.5 % glyphosate or a 2% triclopyr herbicide (formulated product) sprayed to runoff can provide control but repeated applications may be needed. Treat in the fall, when non-target plants are going dormant. Avoid contact with desired plants that are still in leaf.

Gordon Johnson, Extension Horticulture Agent, UD

Nursery - Phytophthora Root Rot

Phytophthora root rot was recently diagnosed in a container nursery. The media was overly wet, pots were in a shaded area, and water was collecting in the area. The following is information on controlling Phytophthora root rot in the nursery.

Prevention - Select nursery sites with well-drained soils. Phytophthora root rot in nurseries can be greatly reduced by improving soil drainage and limiting irrigation. Do not transplant seedlings from infested nurseries into disease-free ones. Avoid using diseased trees for mulch because chlamydospores or oospores may survive in this host material for several years. Avoid movement of equipment between infested and noninfested areas. Diseased seedlings should be lifted separately and destroyed by fumigation or burning. Any effort to save healthy looking trees within diseased areas will result in the spread of the fungus to other areas of the nursery and to outplantings. After working in infested areas, clean equipment thoroughly with steam or an equivalent method.

Chemical - Fumigate soil with methyl bromide and chloropicrin mixture to reduce damage. Unfortunately, fumigant penetration in heavy soils is often inadequate. Metalaxyl, a selective systemic fungicide, is registered as a seed-bed soil drench for seedlings of Fraser fir and Douglas-fir. Two annual applications of metalaxyl are effective in controlling Phytophthora root rot.

Phytophthora root rot progressing up the stem of a seedling.

Information from http://www.forestpests.org/nursery/phytophthora.html

Landscape - Spittlebugs on Leyland Cypress

We have had a rash of reports of small foam patches on Leyland cypress needles. This is spittlebug. No control in necessary. This is more information

On certain evergreens, pine spittlebugs overwinter in the egg stage. When the nymphs hatch from their eggs, they begin to feed. Spittlebugs suck sap out of the plants with their needle-like mouthparts. As the nymphs feed, they excrete spittle that protects them from predaceous mites and insects and keeps them from drying out. There is only one generation per year. In July and August, female pine spittlebugs lay their eggs in dead wood or under the bark of live stems of pines, spruces, firs, hemlock and other conifers. Control is usually not needed. However, heavily infested Leyland cypress, junipers or pines could be treated with Orthene or some other contact insecticide as spittle masses or when the adults are present in early summer. A strong stream of water from a hose could dislodge them enough to make on impact in the home landscape.


Information adapted from the June 6, 2008 edition of the North Carolina Pest News from NC State University.

Landscape - Bagworm Dispersal

The following is information on how bagworms are dispersed in the landscape.

The bagworm, Thyridopteryx ephemeraeformis, is a common defoliator and pest of arborvitae, spruce, juniper, Leyland Cypress and many other species of woody plants in the landscape and in nurseries.

In bagworms the adult female is both wingless and legless, so that dispersal to new locations is totally dependent on the larval, or immature stage. Bagworm eggs spend the winter inside the maternal bag, which is usually attached to the host upon which the mother developed. In spring, the newly-hatched larvae spin strands of silk and drop from the tip of the mother's bag or from the host foliage. The wind breaks the silk at the point of attachment and lifts the insect into the air with the silk trailing, a process referred to as "ballooning".

Bagworms can also disperse to a lesser degree as older larvae by crawling overground. This occurs mainly when the host foliage becomes depleted before the caterpillars have matured.

About 75% of hatched bagworms first formed a tiny bag from silk and covered it with bits of bark. Newly hatched bagworms generally exited from the maternal bag between 9 AM and noon. Most larvae that ballooned without a bag did so in the morning, while those dispersing with a bag did so mainly in the afternoon.

Larvae ballooning from 15 ft height on an 11 mph wind could easily disperse 245 ft downwind without a bag, and 150 ft with a bag. Although dispersing with a bag makes the larva heavier and reduces the distance it can be blown, dispersing with a bag may help the larvae to survive should it fail to land on a suitable host.

50% of the larvae dispersing with bags survived at least 3.5 days off of a host, whereas larvae without bags survived only 1.5 days. The bag seems to provide protection from desiccation and solar radiation, which would be readily absorbed by the dark-colored larva. This may allow time for a larva that is unsuccessful in landing on a host on its first attempt to climb back up to a suitable vantage point so it can balloon again.

Most bagworms hatching from an egg mass disperse from the "parental" host plant regardless of the degree of defoliation. Since progeny from just a few females could completely defoliate a small host, dispersal may be imperative in order to survive. These findings have significance for nurserymen, landscape managers and homeowners who must deal with bagworm problems.

New bagworm infestations originate mainly from ballooning larvae, so failure to control populations upwind from preferred hosts may leave a reservoir of potential dispersants. Since the ballooning period lasts about a month (June in DE) it may be advisable to wait for several weeks after the first larvae are observed exiting from maternal bags before implementing controls. Bagworms are a potential problem each year since most individuals hatching on hosts in wood lots or hedgerows will be ballooning regardless of host condition.

Information from "AERIAL DISPERSAL BEHAVIOR OF THE BAGWORM" by David L. Cox2 and Daniel A. Potter, Department of Entomology, University of Kentucky in the Journal of Arboriculture 16(9): September 1990

Garden - Late Blight

Late blight has been found in Delaware. Potatoes and tomatoes are at risk across the state. We are asking homeowners, master gardeners, and professionals that work with homeowners to be on the look for this disease. Late blight moves very easily across long distances and commercial tomato and potato fields are at risk. If you find this disease in gardens, plants should be destroyed.

Late blight was confirmed this morning on potatoes in Kent County, DE. Hopefully this is not the aggressive genotype that caused the last outbreak, the fact that the stems were not infected at this time and that the infections were not deep in the canopy suggests that the source was airborne sporangia (spores) and this is not the US8 that was so aggressive on potatoes. Samples will be checked to see what genotype it is.

Late blight on potato leaf. Photo by Nancy Gregory, Extension Plant Diagnostician, UD.

Underside of potato leaf with late blight. Photo by Nancy Gregory, Extension Plant Diagnostician, UD.

Late blight appears on potato or tomato leaves as pale green, water-soaked spots, often beginning at leaf tips or edges. The circular or irregular leaf lesions are often surrounded by a pale yellowish-green border that merges with healthy tissue. Lesions enlarge rapidly and turn dark brown to purplish-black. During periods of high humidity and leaf wetness, a cottony, white mold growth is usually visible on lower leaf surfaces at the edges of lesions. In dry weather, infected leaf tissues quickly dry up and the white mold growth disappears. Infected areas on stems appear brown to black and entire vines may be killed in a short time when moist weather persists.

Non-comercial growers and home gardeners should also be on the look for late blight. If found in gardens, it is recommended that the plants be destroyed as there are no fungicide products registered for control in the home garden.

Report from Bob Mulrooney, Extension Plant Pathologist, Plant and Soil Sciences Dept., University of Delaware. Late blight symptom description from the Ohio State University factsheet "Late Blight of Potato and Tomato" HYG-3102-95.

Landscape - Phytophthora in Rhododendrons

Overly wet conditions will mean an increase in Phytophthora diseases in the landscape. One plant very susceptible is Rhododendron. The following is more information.

Watch for Phytophthora shoot dieback and canker on Rhododendrons in shaded wet areas. Leaf spotting and blighting progresses to a dieback of the branch tip. Often the petiole will be brown or black and a V-shaped wedge of blackened leaf tissue will be evident where the petiole attaches to the leaf. Dead shoots are often seen close to the ground first because the fungus will splash from the soil to the leaves. Prune out any infected shoots, cleaning the shears between cuts with rubbing alcohol, 10% bleach or other disinfestant. Professional landscapers can apply Subdue or Aliette; homeowners should use mancozeb or a copper fungicide. Prune rhododendrons so the lowest branches are not touching the soil.

Rododendron wilt, otherwise known as Phytophthora root rot, is caused by the fungus Phytophthora cinnamomi. This fungus infects rhododendron, azalea, mountain laurel, blueberry, heather, Irish-heath, Leucothoe, spike-heath, wintergreen, Arbutus unedo, bear-berry, and Pieris.

In infected plants the leaves become pale, droop, roll downward parallel to the midrib, and wilt. The leaves eventually die. Death may occur in as few as 14 days in susceptible young plants, or death may not occur for up to a year in older plants or less susceptible varieties. Individual branches may die. These branches usually have a canker at their base if the plant is young. Underground, small roots become infected first and turn brown. The roots die, although the plant may grow more roots if the plant is older and established. The fungus grows into the stem and when the bark is cut away, the region where the bark attaches to the wood is dark brown.Some less susceptible cultivars may not wilt until all the roots have died. The youngest leaves may turn yellow between the veins, near the midrib. These areas eventually turn brown. Large, well-established plants often have few aboveground symptoms.

Some varieties of Rhododendron are resistant, including Caroline, Professor Hugo de Vries, and Red Head. A few others are moderately resistant. Some azaleas are also resistant to this disease, including Formosa, Fakir, Corrine Murrah, and the Indica hybrids. It is important to use resistance whenever acceptable, particularly in sites where P. cinnamomi is known to exist.

Information from Bob Mulrooney, Extension Plant Pathologist, UD and the University of Connecticut IPM Website.

Landscape - Wet Weather Nuisance Fungi

Wet weather means nuisance fungi are appearing in turf and landscapes. The following is more information.

The rains are producing calls about slime molds, stink horns, puff balls, and other mushrooms in mulched beds and turf. All of these fabulous fungi are just a nuisance--not pathogenic to plants in these beds or turf. Just rake them out or spray the slime molds with a hose to remove them. They are utilizing the organic matter present as a food source and are doing what comes naturally to them, decomposing and recycling organic matter.

Slime Mold in Turf

Landscape - Insects Currently Active

The following are some insects now active in the landscape in Delaware to be on the watch for.

Dogwood borers appeared in Longwood pheromone traps this week. Four-lined plant bug damage to shrubs perennials has been noted in one or two spots. It appears as small circular holes that look like buckshot on new, but fully expanded leaves. Damage occurred several weeks ago so the control window is gone. Fletcher scale and white prunicola scale crawlers are emerging.. Control crawlers with a foliar absorbed insecticide. Redheaded flea beetle adults are out and feeding. Bagworms have hatched and are feeding now.

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

Landscape - Photos of Insects Now Active

The following are pictures of insect pests now active in Delaware landscapes.

Four-line Plant Bug Adult. Photo from Plant & Pest Digital Library, Purdue University.

White Prunicola Scale Crawlers. Photo from the Branching Out newsletter from Cornell Cooperative Extension.

Fletcher Scale Adults and Crawlers. Photo from the Kansas Department of Agriculture.

Dogwood borer adult female. Photo by James Solomon, USDA Forest Service, Bugwood.org

Hatching bagworm caterpillars from bag of female. Photo from the Texas A&M Landscape IPM website.

Turf - Grub Control Considerations

Preventative grub control is best done on small larvae after eggs have hatched in July. Curative treatments can be done later if infestations are found. The following are some grub treatmetn decision considerations from Rutgers University.

That time of the year is fast approaching. The beetles will be flying and checking out your turf for nice egg-laying sites. Oriental beetles will come first followed by the more in-your-face Japanese beetles within the next three weeks. This is the time to think about white grub management. The question is whether to apply a preventive application that is more expensive and often not necessary, or to take your chances and apply a curative application later if monitoring suggests damaging grub densities.

July would be the best time to bring out any preventive application. However, such preventive applications should be restricted to areas with very low damage threshold and tolerance, areas with a history of white grub infestations, and areas with high beetle activity (egg-laying) in June-July. Remember that the dominant white grub species may vary in Delaware and may include the oriental beetle, Japanese beetle and Asiatic garden beetle. Other species like northern masked chafer and green June beetle can also cause damage in some locations. Keep in mind that species attacking turf can vary to some extent from year to year and can vary dramatically from site to site.

Information adapted from "To Treat or not to Treat: Update on Preventive White Grub Treatments" by Albrecht M. Koppenhöfer, Ph.D., Specialist in Turfgrass Entomology, Rutgers University in the June 26, 2008 edition of the Plant and Pest Advisory, Landscape, Nursery & Turf Edition, Rutgers Cooperative Extension.

Landscape - Diseases Currently Present

The following are some diseases now active to be on the watch for in the landscape.

CEDAR-QUINCE RUST is present on Washington hawthorn, Crataegus phaenopyrum. Symptoms include old swollen twigs from last year and swollen deformed fruit (very evident now). Fungicide control is rarely needed. The same fungus infects serviceberry-- seen this past week. The alternate host is juniper, especially ground cover species. Cedar-quince rust rarely causes any serious damage to the host, just loss of fruit display and dead shoots, which can detract from overall aesthetics.

POWDERY MILDEW is present in many perennials. Look for infection on peony, Monarda (Bee-balm), garden phlox and other susceptible plants. It is controlled well with a number of fungicides (apply at the first sign of disease) as well as hort oil, neem oil, and potassium bicarbonate products.

SCLEROTINA SHOOT BLIGHT OF FORSYTHIA was diagnosed twice last week-- from a homeowner sample and one from my yard. Look for dead shoots that often have an orange discoloration. The fungus infects the blossoms and flower stalks, then grows into the twigs and kills them for some distance. The black sclerotia (fungus fruiting bodies) develop inside the infected twigs and are the best diagnostic sign at this point. Prune and destroy dead twigs and stems.

OAK LEAF BLISTER caused by the fungus Taphrina is a common disease during wet seasons of many oaks in the red oak group but mostly pin oak and red oak. The fungus overwinters in infected buds and infects the newly emerging leaf tissue. Symptoms include scattered circular raised areas of varying sizes up to ½ inch over the upper surface of the infected leaves causing a depression on the corresponding lower leaf surface. Lesions are yellow-green when new and brown with age. This disease causes no defoliation and rarely requires chemical control.

Information from Bob Mulrooney, Extension Plant Pathologist, UD

Landscape - Photos of Diseases from Recent Post

The following are photos to go with the recent post of current diseases in the landscape.

Oak leaf blister. Photo by Michael Kangas, NDSU - North Dakota Forest Service, Bugwood.org

Powdery mildew on Phlox leaf. Photo from Division of Plant Industry Archive, Florida Department of Agriculture and Consumer Services, Bugwood.org

Cedar-Quince rust on Hawthorn. Photo from the Purdue University Plant Diagnostic Lab.

Cedar-Quince rust on Hawthorn twig. Photo from the Purdue University Plant Diagnostic Lab.

Landscape - Cottony Scales

Cottony scales are common in Delaware landscapes. The following is more information on the subject.

Cottony scales get their name from long, white egg sacspresent now. They all cause sooty mold and isolated branch dieback. For ID check the host range and egg laying site.

Cottony maple scale (Pulvinaria innumerablis) occurs on several plants, but particularly silver maple and hickory. Adults and eggs are almost always found on stems and branches, with crawlers settling on leaves for the summer until they migrate back to the stems to overwinter as female scales. Crawler peak is 1388 GDD.

Cottony maple leaf scale (Pulvinaria acericola) occurs on many plants, but most often on maples, dogwoods, black gum, and Pieris. Adults and egg masses are found all over the plant, but mostly on the leaves. They migrate twice after the crawler stage once back to the twigs in the fall and then from the twigs to the leaves in the spring. It is often confused with cottony maple scale (above) or maple mealybug (Phenacoccus acericola), which does not injure plants as severely as cottony maple leaf scale.

Cottony camellia/taxus scale (Chloropulvinaria floccifera) occurs on hollies, sweet box, Cephalotaxus, and its namesake hosts. Like cottony maple scale, it has two migrations per year and the adult females dry up and die after laying eggs leaving only the cottony egg mass on the leaf. Egg hatch from a single mass can take place over 6 weeks. Crawler peak is 830 GDD.

Many predators and parasites feed on these scales; and provide some control. Crawler treatments are the best option as hort. oil in the dormant stage and foliar treatments directed at the remigrating females are ineffective. For cottony camellia/taxus scale, two treatments of horticultural oil at ½ egg hatch and complete egg hatch (~3-4 weeks later) provides the best control with minimum impact on natural enemies. Spring-applied soil systemic neonictinoid insecticides (i.e. Merit, Safari) are also often utilized.

Information from Casey Sclar, IPM Coordinator, Longwood Gardens

Landscape - Pictures of Cottony Scales

The following are pictures of cottony scales to go with the recent post.

Cottony Maple Leaf scale. Photo from North Carolina State University.

Cottony Camelia scale. Photo from the University of Maryland.

Cottony maple scale (Pulvinaria innumerabilis) on a silver maple (Acer saccharinum). Photo by Eugene E. Nelson, Bugwood.org.