Greenhouse - Eriophyid Mites

Eriophyid mites can cause distortions in flowers and other plant parts. The following is information on this pest of greenhouses and nurseries.

Eriophyid mites are extremely tiny (0.3 mm in length), microscopic, spindle-shaped mites with elongated bodies. They resemble sausages with the head and legs located on one end of the body. Eriophyid mites only have 4 legs, which is a unique characteristic among mites. All other mites have 8 legs as adults.

These mites are a specialized group of plant feeders. In general, many eriophyid mites feed on a few closely related species or genera of plants. Eriophyid mites feed deep within the plant tissues sucking out plant juices with their stylet-like mouthparts and transferring a substance, which causes deformation of plant growth. Eriophyid mites live and reproduce within the folds of plant tissues. The eggs are spherical and generally laid in groups. They hatch in less than two weeks into young mites that may take approximately two weeks to a month to mature into adults. Several generations may occur throughout the growing season.

Eriophyid mites can easily come in on plant material from a supplier. If you are a grower examine your plants for eriophyid mites in September and make sure you are not selling customers infested plants. Once damage is evident, it is too late because the mites are already established within the plant. The number of miticides for controlling eriophyid mites is limited. Pest control materials with translaminar properties are your best choices for "managing" eriophyid mites. These would include abamectin (Avid) and chlorfenapyr (Pylon) which can be used in greenhouses only. Additional pest control materials that may work on eriophyid mites, if you can make contact, are pyridaben (Sanmite), fenpyroximate (Akari), and endosulfan (Thiodan).



Reprinted in part from the September 4, 2009 edition of the Greenhouse TPM/IPM Bi-Weekly Report from the University of Maryland Cooperative Extension Central Maryland Research and Education Center http://www.ipmnet.umd.edu/09Sep04G.pdf

Landscape - Current Pests

The following are some current pest problems in Delaware landscapes.

Septoria leafspot is one of several common diseases showing up now on flowering dogwood (Cornus florida) and silky dogwood (Cornus amomum). Some trees have numerous small angular spots on the lower branches that look like small dogwood anthracnose spots. It is too late for any chemical control.

This time of year we often see an increase of anthracnose on oak, maple and walnut. On oak and maple, look for large brown spots that follow the veins and some round spots as well. This late in the season no control is necessary. On walnut, the spots are irregular in shape, numerous and can cause premature defoliation. Again it is too late in the season for any control and the fungus does little to harm the health of the trees.

Puss caterpillars and other stinging caterpillars are actively feeding. Puss caterpillars have been found on Ilex and Acer.

Ground nesting wasps, yellowjackets, and hornets are active and becoming more of a nuisance as we approach fall.

Slime molds have been appearing on lawns especially after recent rains. Slime molds produce a gray growth over the blades of turf that give it a dark appearance from a distance. What you see is the reproductive stage of this primitive fungus. It is not harmful to turf and can be removed by cutting the grass. These are related to the slime molds that appear in mulched beds as white, pinkish red, and yellow blobs often referred to as the “dog vomit fungus”.

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

Landscape - Managing Cool Season Mites

The following is information on managing cool season mites in the landscape. These pests are now active in Delaware.

Cool Season Mites.

This year has been unusually cool, so cool season mites may become active sooner than previous years. Cool season mites such as spruce spider mites and southern red mites become more active as temperature are consistently in the 60's and 70's. Shake a branch or small portion of the plant against a clipboard with a white sheet of paper to monitor mite populations. Mites will begin to move a few moments after shaking and will appear as dots the size of periods. Predatory mites usually move quicker than herbivorous mites and a hand lens will be helpful to recognize the pests. Predatory mites and small lady beetles are common predators of pest mites. Miticides available for controlling these mites include: hexythiazox (Hexygon, Savy), bifenazate (Floramite), abamectin (Avid) and others. Research has shown bifenthrin (Talstar) to cause mite resurgences because it also kills many of the beneficial arthropods helping to keep populations low.

Information from Brian Kunkel, Ornamental IPM Specialist, UD

Landscape - Spruce Spider Mites

Spruce spider mites can build up during cooler weather in late summer. The following is more information.

Spruce spider mites feed on fir, arborvitae, spruce, and other conifers. This mite feeds on older foliage first and damaged foliage has a yellow to bronze coloration. Spruce spider mites begin to feed about 2301- 3957 [3094 peak] GDD base 50 and usually continue until a hard frost. The mite is dark green to dark red after initial feeding and overwinters as a reddish colored egg. The
damage found during the summer on plants is the result of heavy feeding by this mite the previous fall and spring.

Spruce spider mite infestation with webbing. Photo from the USDA Forest Service - Northeastern Area Archive, USDA Forest Service, Bugwood.org

Information from Brian Kunkel, Ornamental IPM Specialist, UD

Landscape - More on Botrytis Blight in the Landscape

The following is more information on botrytis blight (gray mold) in the landscape.

As the weather cools and more dew forms in the evenings, conditions become ideal for the development of Botrytis blight or gray mold. To reduce this fuzzy, gray fungus, keep rose gardens and flowers beds dead-headed and spray with Daconil or Fungonil (chlorothalonil), Cleary's 3336 (thiophanatemethyl) or other labeled fungicide. Other fungicides for commercial use include Chipco 26019 (iprodione) and Decree (fenheximide) or other labeled fungicides. Often the fungus causes a stem canker when infected flowers fall into the plant canopy. Black or caramel-colored, sunken and elongated lesions, with a definite outline, frequently appear on succulent stems or stalks of such ornamentals as begonia, geranium, annual vinca, peony, rose, snapdragon and many other annuals and perennials. Infection also may spread through the stem causing it to be weakened, girdled, and collapsed at the point of infection followed by wilting of the foliage above the lesion.

Information from Bob Mulrooney, extension plant pathologist, UD.

Landscape - Southern Red Mites

Watch for increased southern red mite activity as cooler weather continues. The following is more information.

Southern red mite adults and nymphs are active from 1913 -3518 [2933 peak] and 240 -3584 [3034 peak] GDD base 50 respectively. This mite feeds azaleas, camellias, hollies, photinia, and many others. Southern red mites generally feed on the underside of leaves causing them to turn brownish to grayish and damaged leaves may drop prematurely. This mite is dark red to brownish and has a pale stripe. Eggs are brownish to reddish and have a fine hair coming off the center.

Southern red mite highly magnified. Photo by Jim Baker, North Carolina State University, Bugwood.org

Information from Brian Kunkel, Ornamental IPM Specialist, UD

Landscape and Nursery - More on Japanese Maple Scale

The following is more information on Japanese Maple Scale from the University of Maryland. This pest is on the increase in the region.

Japanese Maple Scale

We are finding 2nd generation crawlers of the Japanese maple scale active this week. The crawlers are purple and if you flip over the female covers you will see the purple colored females and the purple eggs she lays (as hown in photo). If you plan to make an application of Distance or Talus now it is the time to do it.

We are conducting trials at two Maryland nurseries for control of Japanese maple scale. Back in June these nurseries applied the insect growth regulator Talus and horticultural oil at the 1% rate for control of Japanese maple scale crawlers and early instars. The material worked well in killing newly settled crawlers and 2nd instars for about 3 weeks. The interesting thing is that the first generation females continued to lay eggs past this 3 week period. What we are seeing at the sites where Talus was used is that the 2nd generation crawlers are not present yet. We suspect that since we wiped out the early developing scale this took out the population that is producing crawlers at other locations. We plan to delay the next application at these two sites until crawlers start to show up.

Reprinted in part from the August 28, 2009 edition of the TPM/IPM Weekly Report for Arborists, Landscape Managers & Nursery Managers from University of Maryland Cooperative Extension

Landscape - Botrytis Blight

Watch for Botrytis blight in annual and perennial beds. The following is more information.

Botrytis flower blight and stem canker is often present this time of year on annuals and perennials. The cooler weather and prolonged dews will favor Botrytis. Remove spent infected blossoms to prevent the fungus from moving from the flowers to leaves or stems. Stem cankers can develop on roses if old flowers are not pruned and the fungus proceeds to the stems. Look for the tan to gray fluffy fungal growth on the flowers or stems. Fungicide applications of Daconil, or thiophanate-methyl can be helpful in controlling Botrytis in the landscape along with sanitation measures.

Information from Bob Mulrooney, Extension Plant Pathologist, UD.

Landscape - Azalea Caterpillars

Azalea caterpillars can be active this time of year. The following is more information.

The female Azalea caterpillar moth lays clusters of eggs on the underside of leaves, and caterpillars feed gregariously. Early instars appear red with four white to yellowish longitudinal lines down each side. Older larvae have read heads, red legs, and black bodies with white to yellowish 'broken' longitudinal lines down each side. This gives older larvae a spotted appearance. Young caterpillars skeletonize leaves, and as larvae age, they consume entire leaves. Caterpillars will raise both ends off of leaves when disturbed, thus displaying a C shape. Control options when larvae are small include Bacillus thuringiensis (kurstaki), Conserve SC, Sevin, or pyrethroid insecticides.

Azalea caterpillars in mass. Photo by Arnold T. Drooz, USDA Forest Service, Bugwood.org

Information from a past issue of the UD Ornamentals Hotline Newsletter.

Landscape - European Hornets Out Now

European hornets are now active in Delaware landscapes feeding on ripe fruits. The following is more information on this insect.

The European hornet is a large wasp resembling a yellow jacketsbut much larger. The European hornet is about 35 mm (1.5 inches) long and is brown with yellow markings. Nests are rarely constructed in open areas and are more likely to be found in protected areas such as tree cavities, bird houses, barns, or sheds. During the summer, these hornets feed on large insects such as caterpillars, grasshoppers, flies, and bees. European hornets damage a number of ornamental trees and shrubs including, lilacs, rhododendrons, birch, ash, and dogwood. The hornet gains nourishment from the plant sap and the bark may be used as nesting material. Workers expand the nest throughout the summer, and in the fall the next season's queens mate with newly emerged male hornets. European hornets feed on substances high in carbohydrates in the fall. These food sources include overripe fruits, tree sap, soft drinks, juices, and possibly honeydew produced by insects such as aphids or scales. This hornet is also known to attack small fruits such as grapes and consume the sugars. European hornets do not reuse nests and populations die off with the onset of cold weather. The only effective method of control is nest removal. A pressurized wasp and hornet spray with a range of 10 15 feet is desirable. Treatments should be made at dusk or after dark to ensure most of the hornets are in the nest. Caution should be used when treating hornet nests since hornets guard the nest, can sting repeatedly, and can fly at night.

European Hornet. Photo by Jessica Lawrence, NC State Entomology Department, Bugwood.org

Information from Brian Kunkel, Ornamental IPM Specialist, UD

Greenhouse and Nursery - Pythium Rot on Mums

We often see Pythium problems on mums in Delaware. The following is an article on this disease that is a problem this year in many areas of the Northeast due to the wet weather.

The 2009 growing season for fall mums has presented real challenges for the growers. The cool and wet weather of June and early July were less than ideal conditions for growing fall mums. As the summer progressed many growers pushed the mums with fertilizer trying to keep the mums in a vegetative state. Now in late August the varied weather has brought on diseases common to fall mums. A Pythium species, most likely Pythium aphanidermatum, was observed in roots and stems of the specimens from several growers. Symptoms of Pythium attack vary with temperature, moisture, and the species of Pythium involved. The first symptom is often a wet, black basal rot which extends several inches from soil surface. Affected plants wilt and collapse rapidly. Often the fungus invades leaves touching the soil and progresses into the stem at the node, causing a black lesion. In such cases, plants may not exhibit root and basal stem rot. Root rots are also common in Delaware.

Pythium is favored by high fertility and high moisture; avoid overwatering and overfertilizing. Pythium is a natural inhabitant of the soil and can survive there indefinitely as well as in dirt and debris in the greenhouse. Use soilless growing media media. Keep hose ends off the floor and avoid contaminating growth medium with soiled hands, tools, or flats. Fungicides for controlling Pythium include Aliette, Alude, Banol, Banrot 40 WP, Subdue Maxx, Stature DM (drench) Terrazole 35 WP, and Truban 30 WP. Many greenhouse isolates of Pythium are resistant to Subdue. Recommend a drench with a systemic chemical, followed by a sprench to target lesions above soil line. Avoid consecutive applications of fungicides within the same chemical class: rotate among different active ingredients' mode of action for best results.

Stem rot on mum caused by Pythium. We also see root rots caused by Pythium in Delaware. Photo by P. Lopes, University of Massachusetts.

Information from M.Bess Dicklow, Extension Plant Diagnostic Clinic and Paul Lopes, Floriculture and Greenhouse Crops Program in the New England Greenhouse Update http://www.negreenhouseupdate.info/index.php/august/508-chrysanthemum-garden-pythium-stalk-rot

Landscape - Orangestriped oakworms

The following is information on Orangestriped Oakworms from North Carolina State University. This is an occasional pest in Delaware.

Orangestriped oakworms are sometimes very abundant on oaks in summer. They occasionally feed on other hardwoods as well. The moth is brown in color with a white spot and a dark stripe on each forewing. The moths emerge in June and July and deposit their eggs in clusters of several hundred on the underside of oak leaves. The eggs hatch in about a week. The tiny, green caterpillars eventually grow into attractive black caterpillars with yellow or orange stripes running lengthwise along their bodies. Young caterpillars feed in groups whereas older caterpillars tend to be solitary, although there may be thousands of caterpillars on a single tree. Small trees are sometimes defoliated completely by midsummer.

As the caterpillars mature, they are often seen crawling along sidewalks, driveways and yards. These caterpillars may wander for a considerable distance while searching for a place to pupate. You can step on these without fear, as long as you have on shoes. They dig into the soil three or four inches and pupate there. There is usually one generation per year, and the caterpillars overwinter as pupae in the soil. Control is complicated by the size of many of the infested trees. Most people do not have sprayers that can reach very high into shade trees, and by the time the caterpillars descend and crawl about on the soil they are extremely resistant to pesticides. Fortunately, late summer defoliations are much less damaging to the health of trees than early spring defoliations. In most cases it is probably better to rely on birds, diseases and parasites to lower the population next year.

For more information, see http://www.ces.ncsu.edu/depts/ent/notes/O&T/trees/note139/note139.html. If you would like to consider boosting the paper wasp predator population with nest boxes in the spring, see http://www.ces.ncsu.edu/depts/ent/notes/Other/note121/note121.html.

Orangedstriped oakworm. Photo by David Cappaert, Michigan State University, Bugwood.org.

Information from Steve Bambara, Extension Entomologist in the August 28, 2009 edition of North Carolina Pest News http://ipm.ncsu.edu/current_ipm/09PestNews/09News20/pestnews.pdf

Landscape - Powdery Mildew Showing Up on Crape Myrtles This Year

Powdery mildew has been showing up on crape mrytles this year, even in resistant varieties. The following is more information.

Powdery mildew on crape myrtle has not been a problem for many years since the introduction of new cold tolerant varieties (devl. at the National Arboretum and other places) that also happen to have powdery mildew resistance. But, this season has been so favorable for powdery mildew (especially the last several weeks) that we have seen powdery mildew on flower trusses of some of these cultivars. Remember resistance is not immunity. While levels have been low, homeowners have probably never seen powdery mildew on their crape myrtles before. While infection doesn't affect overall plant health, it may be severe enough to prevent flower buds from opening.

Information from Bob Mulrooney, Extension Plant Pathologist, UD

Landscape - Leopard Moth Caterpillar Damage

The following is information on damage from Leopard moth caterpillars, a pest you may see in Delaware.

At 2-3” long, the leopard moth (Zeuzera pyrina) is a large moth, introduced from Europe/N. Africa and found May-September in Delaware. Adults have black and white spots on their wings. Early symptoms of damage from Leopard mothe caterpillars are girdled or broken twigs and branches with wilted/yellow foliage. Monitor trees for branch and limb dieback, which may be mistaken for squirrel activity. Scout dead limbs for exit holes (possibly with silk coverings and resin flow) at the end of broken stems. Fine white frass pellets and possibly pupal skins may be left in bark crevices and inside these galleries.

Larvae damage over 125 tree species incl. oaks, maples, lilacs and apples. They have an unusual life cycle (2 years or longer). Several yellow eggs are laid in small clusters usually in bark crevices. After 10 days, newly hatched larvae crawl some distance before burrowing into a young branch and tunneling into the heartwood to begin feeding. When a branch is too small, the caterpillar exits the branch, migrates along the outside, and tunnels into a larger branch to complete its next caterpillar stage. At the end of the first year, caterpillars are 1” long, yellow with dark spots. At maturity (2”), tree branches up to 3.5 inches and tree trunks may have been fed upon. Pupation occurs in its final gallery.

Leopard moth seems to strike only individual trees and does not spread rapidly. Female moths are not strong fliers. Spread may be through infested nursery stock. Control by pruning out affected limbs/branches. Woodpeckers, other birds and squirrels are important biological controls. As with all borers, growing a healthy tree is the best defense against injury. Chemical control is not practical because of the lengthy flight time. Note that this species shouldn't be confused with the Great/Giant Leopard Moth (Hypercompe scribonia) a native woolly bear caterpillar.

Leopard moth. Photo by James Solomon, USDA Forest Service, Bugwood.org

Leopard moth caterpillar tunnelling in wood. Photo by James Solomon, USDA Forest Service, Bugwood.org

Information from Casey Sclar, IPM Coordinator, Longwood Gardens and Emma Seniuk, Professional Gardener Student, Longwood Gardens

Landscape - Diplodia Tip Blight in Pines

This time of year, tip blight in some pines is very evident. The following is more information:

Austrian and Mugo pines growing in landscapes are showing the effects of infections by the Diplodia tip blight fungus, Diplodia pinea. The disease is noticeable in landscape pines now. Austrian, Mugo, and Scots pines are often planted in landscapes because of their dense, green foliage and symmetrical shape. When healthy, a grouping of Austrian pines can form an attractive year-round screen. Diplodia tip blight, also known as pine tip blight, or Sphaeropsis tip blight, is a devastating disease worldwide, but especially here on exotic two-needle pines such as Austrian pine (Pinus nigra), Mugo pine (P. mugo) and Scots pine (P. sylvestris) in landscape settings and Christmas tree plantations.

Tip blight symptoms on Austrian pines first appear on the newly elongating candles (shoots) in late April to early May. As its name indicates, the shoot tips are killed very quickly and by late May, the diseased tips are noticeably necrotic and stunted. Needles, even before they are out of the needle sheaths, start to turn a straw brown color and droplets of resin can be seen exuding from these dead needles. Some of the diseased needles may begin to break out of their sheaths, but often their growth is halted resulting in stunted, dead needles. Symptoms on Austrian pines are most characterized as progressing from the shoot tip inward. Over a few days to a week all of the needles on infected candles will turn brown and die and shoots will appear brown through late summer. The candle as a whole will be stunted, necrotic, and eventually brittle from resin exudation. The necrotic shoot and needles can sometimes give these dead tips a gray color.

As the fungus progresses from the tip back towards the trunk, older needles will turn straw color and die. This generally happens later in the year or the following year. Progression of the fungus can lead to branch dieback and eventually death of the tree. These symptoms typically start in lower branches of the tree and progress toward higher branches year after year until the tree dies or is so damaged it needs to be removed. On landscape Austrian pines disease symptoms generally begin to appear after trees reach cone-bearing age, typically 12-13 years old. Close examination of infected shoots will often reveal the presence of tiny black dots (pycnidia) on the base of infected needles. Pycnidia are black fungal structures embedded in and protruding through the host tissue, and in D. pinea are only produced on dead host tissue, such as cone scales and dead needles. Pycnidia are tiny but can be seen with the naked eye, resembling black pepper sprinkled on the dead cones and needles. It is not uncommon to see dead cones and needles from infected trees covered with pycnidia. The pycnidia release spores in warm, rainy spring and summer weather which we have had in abundance this year. These spores are dispersed by rain splash and windblown rain.

Pines are most susceptible to D. pinea infection in spring when shoots are just elongating and not yet lignified. As the fungus colonizes the host, it kills the host cells resulting in necrotic symptoms and sometimes resin production. An additional field symptom, canker disease, also is often accompanied by excess resin. After the fungus has killed the host tissue, it can produce pycnidia which can overwinter and be a source of inoculum the following spring.

Information from "Diplodia Tip Blight Is Causing Dead Shoots on Pines" By John Hartman in the current edition of the Kentucky Pest News. For the full article with pictures go to http://www.uky.edu/Ag/kpn/kpn_09/pn_090825.html#Landscape

Landscape - Current Pests

The following are pests you should be on the watch for now in Delaware landscapes.

Clearwing borer populations (Lilac/Ash, Dogwood, and others) are prevalent. Protect trees as needed with pyrethroids like permethrin or bifenthrin.

Watch for building whitefly populations on annuals and select perennials. Parasites may move in and turn the normally yellowish nymphs black or other management strategies may be required.

The USDA has initiated a citizen survey for the Asian longhorned beetle (not yet ID’d in DE). Interested persons may receive a letter and identification sheet, along with a card to return to report findings. Call the PLSC office (302-831-2534) for materials.

Japanese maple scales have been found in egg & crawler stage in Kent County.

Puss caterpillars were found feeding on Ilex & Acer. This caterpillar has a nasty sting associated with its hairs, so be careful moving plant material. Feeding damage is not severe on plants so treatment is not often warranted.

Tuliptree & magnolia scale crawlers are approaching peak crawler activity. Horticultural oil, Insecticidal soap, Distance are good products for crawler control.

Information from the "What's Hot" section of the Ornamentals Hotline Newsletter from the UD Cooperative Extension Ornamentals Group.

Turf and Landscape - Weed Seed Bank

With the ample moisture provided by recent rains, I see many turf areas and landscapes with weeds going to seed at this time. This will add to the weed seed bank and make weed management more challenging in the future. The following is more information.

Weed Seed Bank is a term used to describe the reservoir of viable weed seeds on the surface or in the soil profile. One major weed management goal in turf and landscapes should be to reduce the weed seed bank. Late summer is a major challenge because many weeds such as crabgrass are going to seed, especially in low maintenance areas. This adds to the weed seed bank and will make future weed control more challenging. It takes several years with no additions to the seed bank to reduce weed pressure. This is because of dormancy mechanisms allowing some weed seeds to remain viable for years.

The key to managing the weed seed bank is to not let weeds go to seed. For crabgrass, to get a 75% reduction in the seed bank, it will take 3 years of active control measures making sure there is little seed head production. To reduce weed seed head production in turf, mow more frequently using very sharp blades. This is especially critical in late summer. One challenge is low growing weeds that produce seed heads below the height of mowing. Herbicides will be your best option in that case (for large multi-tillered crabgrass use quinclorac – Drive herbicide). There are also some growth regulators registered for seed head suppression in specific weeds such as annual bluegrass.

Gordon Johnson, Extension Agriculture Agent, UD, Kent County

Landscape - Dog Day Cicada

You often will see dead or dying cicadas at this time of the year in the landscape. This is the dog-day cicada. The following is more information.

Annual Cicadas Are Very Active in August

In August you will often hear pockets of male annual cicadas drumming on their abdomens to attract female mates. The dog day cicada was given this common name because they are active during the celestial occurrence of the dog star formation in the sky. These large, greenish cicadas are an annual event and really do not cause the extensive damage that the 17-year female cicada does to tree branches. In late August your customers will find the annual cicada on the ground dying after mating and egg laying. Control is not necessary for the dog day cicada.

Dog Day Cicada. Photo by David Cappaert, Michigan State University, Bugwood.org

Information from the August 21, 2009 edition of the TPM/IPM Weekly Report for Arborists, Landscape Managers & Nursery Managers from the University of Maryland Cooperative Extension

Greenhouse and Nursery - Early Flowering in Mums

We are seeing earlier flowering in mums this year. The following is more information.

Chrysanthemums Flowering Early

Many greenhouse growers put out their mums this year withput pinching or without Florel applications. The cool nights of late July and August have made many of these mums set flower buds early. The result is that many mums are shorter than normal and the flowers will be opening at the end of August to early September. A couple of growers made multiple applications of Florel this season and their plants are still vegetative and appear to be larger in size. It is a tough call each season whether you should apply Florel or not. This season it would have been a good idea. Hopefully, early mum sales will be good.

Information from the August 21, 2009 edition of the Greenhouse TPM/IPM Bi-Weekly Report from the University of Maryland Cooperative Extension, Central Maryland Research and Education Center

Landscape - Foliar Nematodes on Perennials

The following is information on foliar nematodes in perennials. Be on the look for this pest in the last weeks of summer.

Foliar nematode injury will increase as perennial foliage ages and we get more leaf wetness from dew and rain. Be on the lookout for symptoms of this nematode pest causing premature dying of foliage in the garden. It is easily overlooked or misidentified. The main symptoms are the angular spots on the leaves limited by the vein pattern of the leaf. The wet weather will be getting aids in movement of the nematodes over the leaf surfaces since they swim in a film of water then enter the leaves through stomata. The host range is very large including popular plants such as hosta, peony, anemonies, ferns, bugbane, plumbago, and many others. Remove infected leaves and destroy them. We still do not have any effective chemical controls for the home or commercial landscape.

Information from Bob Mulrooney, Extension Plant Pathologist, UD

Turf - Recommended Turfgrass Varieties

With late summer or fall planting coming up for turfgrasses, I thought I would reprint the current recommended varieties from the Maryland/Virginia turfgrass variety working group. We would recommend these varieties for mid-state and lower Delaware.

2009-2010 Virginia-Maryland Turfgrass Variety Recommendations

Authors as Published: Mike Goatley, Turfgrass Specialist, Virginia Tech; Whitnee Askew, Research Associate, Virginia Tech

The Maryland-Virginia Turfgrass Variety Recommendation Work Group meets each Spring to consider the previous year’s data from Virginia and Maryland National Turfgrass Evaluation Program (NTEP) trials and to formulate these recommendations. Virginia and Maryland variety recommendations are essentially identical except for specialized grasses and research situations that differ due to adaptation and state regulation. To qualify for this recommended list turfgrass varieties: 1) must be available as certified seed or, in the case of vegetative varieties, as certified sprigs or sod; 2) must be tested at sites in both Virginia and Maryland; 3) must perform well, relative to other varieties, for a minimum of two years to make the list as a “promising” variety and for three years to make the recommended category. All test locations in Virginia and Maryland are considered in making these recommendations. Seed availability may vary between turf seed suppliers. Some species and varieties may have limited adaptation.

Kentucky Bluegrass – Individual varieties selected must make up not less than 10%, nor more than 35% of the total mixture on a weight basis. All varieties must be certified. Selections can be made from Category I alone or various combinations of Categories I, II, and III as noted. Kentucky bluegrasses listed as “Promising” (Category III below) can account for no more than 35% of the blend by weight).

Category I – Recommended Kentucky Bluegrass Varieties (65–100% of blend by weight).
Award, Awesome(3), Beyond, Bordeaux(3), Brilliant, Cabernet(3), Courtyard, Diva, Everest(3), Everglade, Excursion, Glenmont(1), Impact, Juliet, Liberator, Midnight, Moonlight(3), NuDestiny, NuGlade, Princeton 105, Quantum Leap, Raven, Skye, Sudden Impact, Total Eclipse(3), and Touche.

Category II – Promising Kentucky Bluegrasses (10–35% on a weight basis) – These grasses have performed in the top statistical quality category for a minimum of 2 consecutive years in Virginia and Maryland trials. Seed may be difficult to locate for some cultivars. Note: Durablue, ThermalBlue, and ThermalBlue Blaze are commonly referred to as Hybrid Bluegrasses, but they are classified by USDA as Kentucky bluegrasses. To date they have had better performance in traditionally warmer areas of Virginia.
Alexa II, Aries, Aura, Barrister, Belissimo, Bewitched, Bluestone, Durablue, Emblem, Everglade, Ginney II, Granite, Mystere, NuChicago, NuDestiny, Rhapsody, Rhythm, Solar Eclipse, ThermalBlue, ThermalBlue Blaze, Wild Horse, Yankee, Zinfandel

Tall Fescue – For tall fescues, both recommended and promising varieties can be used in the VCIA Sod Certification Program.

Category I – Recommended Tall Fescue Varieties (90–100% on a weight basis)
2nd Millennium, Avenger, Biltmore, Bingo, Blackwatch, Bravo, Cochise II(3), Cochise III, Constitution, Coyote II, Crossfire II(3,4), Davinci(3), Daytona(3), Endeavor(3), Falcon IV, Fidelity, Forte, Good-En(3,4), Grande(4), Grande II, Greenkeeper WAF, Guardian 21, Houndog 5, Hunter, Inferno, Justice, Magellan, Masterpiece, Matador(3), Matador GT(3), Onyx(3,4), Padre, Picasso(3), Penn 1901, Raptor, Rebel Exeda, Regiment II, Rembrandt(3), Southern Choice II(3), SR 8250(3), Taos, Tarheel, Tarheel II, Tempest, Titanium, Tombstone, Turbo, Ultimate(3), Watchdog, and Wolfpack.

Category II – Promising tall fescue varieties (may be 90–100% of the mixture on a weight basis)
3rd Millenium SRP, Aggressor, Aristotle, AST 7002, AST 7003, AST 9003, Braveheart, Bullseye, Cannavaro, Catelyst, Cezanne RZ, Cochise IV, Compete, Escalade, Einstein, Essential, Faith, Falcon V, Falcon NG, Fat Cat, Finelawn Xpress, Firecracker LS, Firenza, Gazelle II, Greenbrooks, Guardian 21, Hemi, Hudson, Jamboree, Lindbergh, Monet, Mustang 4, Ninja 3, Raptor 2, Rebel IV, Renovate, Reunion, Rhambler SRP, Rocket, Shenandoah, Shenandoah Elite, Sidewinder, Speedway, Spyder LS, SR 8550, SR 8600, SR 8650, Stetson II, Tahoe II, Talladega, Terrier, Titanium, Toccoa, Traverse, Trio, Tulsa Time, Umbrella, Van Gogh, Wolfpack II

Kentucky bluegrass varieties recommended for mixing with tall fescue sod to enhance sod strength (up to 10% of the seed mixture by weight): All cultivars in Categories I and II above.

Bermudagrass – Varietal differences in texture and winter hardiness are important considerations. If no notation follows the variety name this indicates it has performed in the top statistical category at both Blacksburg and Hampton Roads Research Stations. Varieties with the notation # are only recommended in the warmer regions of Virginia due to concerns regarding their cold tolerance. Note that there are no guarantees regarding winter survival for any recommended or promising variety, and one not noted for cold tolerance might perform well indefinitely in colder regions of the state depending on climate patterns.

Category I – Recommended vegetatively propagated bermudagrass varieties: Aussie Green#, Celebration# , GN-1#, Midfield, Midiron, Midlawn, MS-Choice#, Patriot, Premier, Quickstand, Shanghai, Tifton 10, Tifgreen#, TifSport, Tifway#, Tifway II#, Tufcote, and Vamont.

Category II -Recommended seeded bermudagrass varieties: Blackjack#, Contessa, Transcontinental#, Princess-77#, Pyramid 2#, Riviera, Savannah#, Sovereign, Southern Star#1, Sundevil II#, Veracruz#, and Yukon.

Zoysiagrass – (Varietal differences in texture and winter hardiness are important considerations.)

Category I – Recommended vegetatively propagated zoysiagrass varieties: Meyer. Category II – Recommended seeded zoysiagrass varieties: Zenith, Compadre Category III – Promising vegetatively propagated (V) and seeded (S) zoysiagrass varieties: Cavalier (V), Companion (S), Himeno (V), J-14 (S), J-36 (S), J-37 (S), Marquis (V), Sunburst (V), Zorro (V), ZEN­400 (S), and ZEN-500 (S). Promising for Eastern VA only: DeAnza (V), El Toro (V), Emerald (V), Jamur (V), Miyako (V), Victoria (V), and Zeon (V).

Perennial Ryegrass – (not for use in sod production) Use certified seed.

Category I – Recommended perennial ryegrass varieties:
Affirmed, Applaud, Apple GL, Brightstar SLT, Brightstar II, Buena Vista, Calypso 3, Catalina II, Divine, Exacta, Gator 3, Grand Slam(3), Inspire, Jet, Line Drive GLS, Manhattan 4, Paragon GLR, and Stellar.

Category II – Promising perennial ryegrass varieties (limited data/availability of seed): 1G Squared, Accent II, AllStar 3, Amazing GS, ASP6004, Attribute, Barlennium, Charismatic II, Citation Fore, Dart, Dasher 3, Defender, Derby Xtreme, Exacta II GLSR, Fiesta 4, Fusion, Grand Slam 2, Gray Fox, Harrier, Homerun, Keystone 2, Kokomo II, LS 2300, Manhattan 5 GLR, Notable, Palace, Palmer IV, Phenom, Plateau, Pleasure Supreme, Palmer 5, Primary, Protégé GLR, Prototype, Regal 5, Repell GLS, Revenge GLX, Secretariat II GLSR, Silver Dollar, Soprano, SR 4600, Stellar GL, Transformer, Uno, Zoom.

Fine Fescues – For general use in low maintenance areas or in partial to full shade. Promising varieties have limited performance data or availability as certified seed. Neither blending varieties nor mixing species have been studied extensively in MD or VA. Limited research does not indicate any advantage to blending or mixing varieties from the different fine fescues (e.g.; creeping red, chewings, hard, or sheep fescue). Use only certified seed.

Creeping red fescue – Recommended varieties: None. Promising: Cardinal, Class One, Epic, Fortitude, Garnet, Pathfinder, and Wendy Jean.

Chewings fescue – Recommended: 7 Seas, Longfellow II, SR 5130,. Promising: Ambassador, Compass, Lacrosse, and Zodiac.

Hard fescue – Recommended: Berkshire, Chariot, Discovery(4), Gotham, and Predator. Promising: Firefly, Oxford, Reliant IV, Spartan II, and SR 3000.

Sheep fescue – Recommended or promising: None at this time.

Kentucky bluegrass varieties recommended for mixing with fine fescue sod to enhance sod strength (up to 10% of the seed mixture by weight): All cultivars from Kentucky bluegrass Categories I, II and III

Varieties marked with superscript notations denote the following:
(1) to be considered for removal in 2010 due to declining performance relative to other varieties.(2) to be considered for removal in 2010 due to declining seed quality.(3) to be considered for removal in 2010 due to the absence of recent testing of certified seed lots in MD and VA.(4) to be considered for removal in 2010 due to lack of recent testing in MD and VA.
Rights

Landscape and Nursery - Deep Planting Problems

I recently was called to look at a christmas tree farm with failing plants. The problem was related to planting too deep. The following is more information on this problem.

Many trees and shrubs are set too deeply from the time of planting, or they settle too deeply over time. A planting depth of only one-inch too deep can cause trouble. It is not uncommon to see trees planted as much as three or more inches too deep. Deep planting causes bark deterioration at the soil line, which will eventually kill the plant. It usually takes a few seasons for a newly planted tree or shrub to die from this. Various symptoms point to excessively deep planting. Some new growth may develop each spring, only to die-off during the stress of summer. Advanced symptoms of depth-related stress are cankers and deep cracking of the bark. A canker is an area of dead tissue on a woody stem. Some shallow cracking of bark is normal for many trees as the trunk grows. A tree may survive until fall but may not survive the winter because of an insufficient storage of food reserves caused by the damaged bark.

Information from "Common Abiotic Plant Problems", Home & Garden Mimeo # HG 86, University of Maryland.

Nursery and Landscape - Deal with Circling Roots in Trees and Shrubs in the Nursery and Before Planting

The following is information on dealing with circling roots in trees and shrubs in the nursery and prior to planting in the landscape.

Dr. Ed Gilman, tree researcher and professor at Univ. of Florida, suggests we need to take drastic steps to correct tree root defects in container grown trees and shrubs. Rather than just slicing, he advises removing the outer inch of the rootball from container-grown trees. To see photos on how to do this, go to http://hort.ifas.ufl.edu/woody/circleremoving.shtml. Any large diameter surface roots should also be cut with pruners just before the points where they kink or bend. New roots should branch from those cuts and grow outwards as nature intended (unless planted too deep, but that is another topic), establishing a good root system for the long run.

These practices can certainly add stress to the tree during establishment, making frequent watering during the first season more critical than ever. Root defects are most common in container production because hitting the container wall disrupts the natural outward direction of root growth, instead causing the roots to circle and/or dive downwards. However, even B&B trees may have hidden root defects from container growing early in the production cycle, or from roots bent when planting bare-root liners into the production field. Once the roots become woody, their kinked shapes are permanent defects.

Good nursery practice includes root pruning each time the plant is stepped up, but that is not always done. If not corrected when planted into the landscape, the circling roots near the trunk continue to enlarge and may end up girdling the stem. Even if stem girdling does not result, few branch roots develop to the outside of circling roots, which can cause the tree to be unstable and have a reduced feeder root system. Most people don’t realize that tree decline and death in 10-20 year old trees may have been predetermined by the root architecture present when planted.

Root defects are less severe on shrubs because they typically have more fibrous and branched root systems than trees. Most shrub root problems can be prevented by purchasing plants that are not root bound and properly planting them in decent soil. Slicing exterior circling roots and removing any matted root layer at the bottom of the pot should give a shrub a good chance of living a long and productive life.

So, to slice or not to slice? I say “yes”, do slice but don’t stop there. The green industry as a whole needs to address root defect problems from propagation to landscape establishment, to help stem the epidemic of tree failures in the landscape. As a landscaper, retailer or producer, you can help by inspecting roots and refusing to buy (or sell) trees and shrubs which are rootbound or have visible root defects. Growers should consider using containers which have been designed for air-root pruning and step up unsold trees and shrubs into larger containers rather than holding them in the same pots once roots begin to circle. Teach your workers how to prune roots when transplanting, whether the plant is going into a larger container or into the landscape.

Information from Cathy Neal, Ph.D., Specialist in Ornamentals, University of New Hampshire Cooperative Extension Adapted from her article in News & Views for New Hampshire’s Green Industry, University of New Hampshire Cooperative Extension, July 2009.

Landscape - Oak Skelelatonizer

The following is information on the oak skeletonizer, an insect pest of oaks in DE.

The oak skeletonizer is a native insect that has two generations per year in our area and is active from 547--2846 GDD base 50. The second generation is usually sometime during late July to August. The larvae are yellowish green and prefer to eat red oaks, but also feed on chestnuts and other oak trees. Early instars feed as leaf miners, but older larvae feed externally and skeletonize the leaf. Mature larvae drop from leaves on silken threads when disturbed. Populations vary by year, thus some years damage may not be noticed. Severe infestations or repeated attacks by this insect can result in crown thinning, die back, and possibly increase the trees susceptibility to other pests such as borers. Larvae form white ribbed cocoons on the leaves, twigs, or other nearby structures. Control options include B.t., bifenthrin, deltamethrin, cyfluthrin, or cyhalothrin.

Oak skelatonizer larvae, cocoons and defoliation on underside of leaf. Photo from James Solomon, USDA Forest Service, Bugwood.org

Information from Brian Kunkel, Ornamental IPM Specialist, UD

Landscape - More on Bacterial Leaf Scorch on Oaks

The following is more information on bacterial leaf scorch of oaks which can be seen in Delaware landscapes at this time.

Bacterial leaf scorch on oaks in the red oak group can be found now. Infected trees have leaves with brown leaf margins (like drought damage). Since we have not been in a drought, lack of water is an unlikely cause of the symptoms, but since the bacterial infection restricts water flow, drought symptoms appear. This is a debilitating disease that can take several years to a decade to kill the tree and there is no cure. Symptoms can be reduced or masked with oxytetracycline injections, but trees cannot be cured. Plant hoppers vector the bacteria from symptomless weed hosts and transmit it to oaks during feeding. If you have suspect trees, tests will confirm the presence of the bacteria in leaf petioles. Contact the Plant Diagnostic Clinic at 320-831-1390 or on the web for more information on testing. The web has many articles on BLS-- here is a good one http://www.apsnet.org/online/feature/bls/

Leaf scorch symptoms on red oak. Photo from the Minnesota Department of Natural Resources Archive, Minnesota Department of Natural Resources, Bugwood.org

Information from Bob Mulrooney, Extension Plant Pathologist, UD.

Landscape - Yellownecked Caterpillars

You may see yellownecked caterpillars feeding in trees this time of year. The following is more infomation.

Yellownecked caterpillars have a jet black head, yellow and black stripes and some white hairs. Directly behind the head is a bright yellow-orange segment. Oaks are often attacked along with basswood, maples, elms, walnut, fruit and nut trees. Adults emerge during June-July, mate, and females lay eggs on the undersides of leaves. This caterpillar feeds gregariously, skeletonizing leaves as early instars and consuming most of the leaf when they are older. When disturbed, larvae assume a “Ushaped” defensive posture to reduce the likelihood of attack by predators and parasitoids. Larvae actively feed between July through September depending on location and when eggs were laid, but there is only one generation per year. Birds, predatory insects, and parasitoids attack this pest. This pest seldom causes serious harm to trees and treatments are not often warranted. Chemicals available for control include B.t., spinosad, azadirachtin, or one of the pyrethroids.

Yellownecked caterpillars. Photo by Gerald J. Lenhard, Louisiana State Univ, Bugwood.org

Information from Brian Kunkel, Ornamental IPM Specialist, UD

Turf - Seeding Turf

With turf seeding period coming up, the following are some general guidelines to follow.

Late summer or early fall is the ideal time to seed turf grasses. The following are some points to consider for these seedings. Before seeding, address any problems that would affect turf growth (weeds, fertility, compaction). Purchase high quality seed with a recent germination test. Use improved turf varieties, with good disease resistance, adapted to our transition area (turf-type tall fescue for most general applications). Go to http://pubs.ext.vt.edu/2907/2907-1397/2907-1397.html for recommended varieties from the MD-VA turfgrass working group. Single varieties or mixtures of several varieties of the same species with similar appearance and growth habit are recommended for uniform sites. Mixtures of 2 or more species (such as turf-type tall fescue with creeping red fescue) are often used where multiple environments exist in the same property such as mixture of partially shaded and open areas. However, in a multi-species mixture, the best adapted species will be dominant. Seed into moist soil conditions or provide irrigation to achieve good germination. Soil-seed contact is critical for germination – use a packer type seeder for new seedings or complete renovations; use a slit seeder for partial renovations into existing turf. The ideal seeding period in Delaware is from the last week in August through the month of September. Grass seedling survival is greatly improved if there is 4- 6 weeks of growth before a hard frost.

Gordon Johnson, Extension Horticulture Agent, UD, Kent County

Landscape - Bacterial Leaf Scorch

Hot weather in mid-summer is the time that you often see bacterial leaf scorch on infected trees. The following is more information.

Bacterial leaf scorch (BLS) is a disease with a name that definitely understates the impact on infected trees. It causes far more than leaf scorching. The bacterial pathogen can slowly kill mature trees in 8-10 years.

Here's what you may see. About mid-summer, infected trees appear to have environmental leaf scorch. The same trees appear healthy again the next spring, but scorching returns each summer, becoming progressively worse over 5 or 6 years, thinning the canopy and eventually killing the tree. I have seen the problem on Illinois oak trees, but other trees may also host this disease.

Bacterial leaf scorch is an infectious plant disease caused by a bacterium called Xylella fastidiosa. The pathogen is systemic, living only in the xylem. The most frequent hosts of this disease in the U.S. include elm, oak, sycamore, mulberry, sweetgum, sugar maple, and red maple. At the University of Illinois Plant Clinic we have confirmed BLS on pin, red, shingle, bur, and white oaks. Kentucky pathologists report BLS on pin, red, scarlet, bur, white, willow, and shingle oaks; silver, sugar, and red maples; sweetgum, sycamore, planetree, hackberry, American elm, and red mulberry. Look for scorch symptoms that occur in early summer to midsummer and then intensify in late summer. The scorched leaf edges or tissue between veins may be bordered by a yellow or reddish-brown color, but not in all cases. The symptoms may occur first on one branch or section of branches and slowly spread in the tree from year to year. The pin oaks we have seen infected have general thinning. It is one of those situations that you hope will be better next year but only gets worse.

There is no cure for this disease. Some have tried injections with oxytetracycline, but none have shown more than disease suppression with this antibiotic. Since the pathogen is in the xylem, cleaning pruning tools before moving to another tree is important to reducing spread of the disease. Xylem-feeding leafhoppers and spittlebugs are thought to spread the bacterium in landscape trees. Transmission between trees through root grafts has been reported.

Unlike most other bacteria, Xylella fastidiosa cannot be isolated in the lab. However, it may be confirmed using serological techniques. ELISA (enzyme linked serological assay) testing can be done and is used to help identify the Xylella pathogen. The most reliable test results occur in August and September, possibly because the bacterial population in trees is higher late in the season.

Bacterial leaf scorch on oak. Photo by Randy Cyr, Greentree, Bugwood.org

Information reprinted from an article by Nancy Pataky in the current edition of the Home, Yard, and Garden newsletter from the University of Illinois http://hyg.ipm.illinois.edu/article.php?id=100

Turf - Core Aeration for Thatch Management

Core aeration is a good way to manage excess thatch buildup in turf. The following is more information.

Core cultivation (aeration) can be used to reduce thatch accumulation, modify the physical characteristics of thatch, and remove thatch from the soil-turf interface. A single treatment may not be as effective as dethatching in removing thatch debris, but it is less injurious and disruptive to the turf. The soil cores removed with core cultivation should be redistributed throughout the turf and thatch layer. This can be done by allowing the soil cores to dry and then dragging the cores with a steel mat or chain link fence. A dethatcher can also be used to break up soil cores. The redistribution of the soil cores into the turf modifies the physical and chemical qualities of the thatch, making it a better growing medium. Soil incorporation will also enhance thatch breakdown by improving conditions for microbial activity.

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

Turf - Fall Liming

Late summer and fall are good times to apply lime to turf areas. The following are some considerations in liming lawns and turf areas.

Fall is a great time to address soil fertility issues, including liming. Recent soil tests from a reputable lab will give you some guidance on how much (if any) lime would be needed. Two pH figures are reported on a soil test report: pH and buffer pH. The pH figure tells you whether or not you need lime and the buffer pH value tells you how much is needed to reach the target pH for turf (6.0-6.5 for most turf in Delaware).

Raising soil pH is the goal of liming. If magnesium is deficient or low in the soils, those soils may benefit from the application of dolomitic limestone (Hi Mag), though magnesium availability increases with increases in pH; otherwise use calcitic lime (Hi Cal).

A few other things to keep in mind:

1. Tillage is the best way to incorporate lime when doing a new planting or complete renovation. In existing turf, core aeration is a way to move some lime into the root zone of turf and get better response to liming.

2. If surface applying lime, do not apply urea based fertilizers soon after application of the lime. Urea volatilizes much more quickly on an alkaline surface, and nitrogen is lost to the atmosphere.

3. Calcium deficiencies are extremely unlikely in Delaware and most states in the Mid-Atlantic; apply liming materials to adjust pH up, not to supply calcium (which becomes abundant at optimum pH levels). Most of our soils contain abundant amounts of available calcium, and turf uses only a small amount of calcium.

4. Gypsum does not raise soil pH. This includes waste products like ground wallboard.

Adapted from "Liming Considerations for Late Summer and Fall" Keith Diedrick and Robert Mullen in the current edition of the Crop Observation and Recommendation Network Newsletter from the Ohio State University.