Landscape - Oystershell Scales

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

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

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

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

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

Information from Brian Kunkel, Ornamental IPM Specialist, UD.

Compost Use Considerations

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

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

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

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

Greenhouse and Nursery - Chrysanthemum White Rust

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

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

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

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

Information from, Nancy Gregory, Plant Diagnostician, UD

Landscape - Lacebug Feeding Damage

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

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

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

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

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

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

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

Landscape - Wetwood and Slime Flux Disease of Trees

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

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

Symptoms and Cause.

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

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

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

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

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

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

Landscape and Nursery - Japanese Maple Scale Observations

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

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

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

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

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

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

Turf - Causes for Turf Deterioration

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

Causes of turf deterioration

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

Shade problems

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

Poor drainage

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

Soil fertility and acidity

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

Pests

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

Thatch

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

Mowing

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

Species and management

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

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

Landscape - Pine Needle Scale

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

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

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

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

Greenhouse and Nursery - Wet Weather Means Diseases in Mums

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

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

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

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

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

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

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

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

Landscape - Dogwood Sawflies

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

Dogwood Sawflies.

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

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

Information from Brian Kunkel, Ornamental IPM Specialist, UD

Nursery and Greenhouse - Controlling Phytophthora

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

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

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

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

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

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

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

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

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

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

Landscape - Fall Webworms

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

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

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

Information from Brian Kunkel, Ornamental IPM Specialist, UD

Turf - Brown Patch Now Appearing

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

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

Information from Bob Mulrooney, Extension Plant Pathologist, UD.

Education - 4-H'ers and FFA Students and Horticulture at the Delaware State Fair

The Delaware State Fair offers 4-H'ers and FFA students many opportunities to learn about horticulture through 4-H and FFA horticulture contests, demonstrations, and exhibits. The following are a few pictures.

Landscape - Backyards a Focus for the Cooperative Extension at the Delaware State Fair

Backyards were a focus for at the Delaware Cooperative Extension Tent at the Delaware State Fair. This included many horticultural ideas. Commercial landscapers can use this theme in designing landscapes and providing services for their clients - show your clients what their backyard can do for them.

Landscape - Mugwort Control

The following is information on control of mugwort in landscape beds.

Many landscape beds have problems with mugwort (Artemesia vulgaris), also know as wild chrysanthemum. This is a perennial weed that is difficult to control due to its ability to spread by underground rhizomes. Leaves are similar to appearance as chrysanthemum, 2-4 inches long, 1-3 inches wide, simple, alternate, deeply lobed, and are covered with soft, white to gray hairs underneath. Leaves will also have a distinctive smell. Mugwort is most commonly introduced as a weed with nursery stock. It rarely produces viable seed and spreads almost exclusively by rhizomes.

Hand weeding is often only partially effective because complete control requires removal of all the underground rhizomes. One fairly effective control approach is to use directed applications of glyphosate, one in late summer and one in early fall. Dichlobenil (Casoron) granular herbicide, winter applied, has given good mugwort control in beds with woody plants such as junipers; however, Casoron is not labeled for all species and injury can occur on newly planted trees and shrubs. Clopyralid (Lontrel) has given up to 95% control of mugwort in some trials as a selective application. However, clopyralid is only labeled for use around the following woody species: dogwood, oak, fir, pine, red maple, spruce, sycamore, arborvitae, boxwood, juniper, some Rhododendron species, spirea, and yew. A better fit for Lontrel is suppression of mugwort in ornamental grasses where it can be used as an over-the-top application for many grass species.

Gordon Johnson, Extension Horticulture Agent, UD, Kent County

Landscape - Velvet Ants

You may come across velvet ants in the landscape. The following is more information on these insects.

Velvet ants are striking insects covered with red and black or orange and black "hairs". Females are wingless; males have two pairs of black wings. The female have very long stingers, the potency of the punch is reflected in the common name "cow killer wasps". Picking one up can provide a memorable experience. These wasps, seen walking determinedly across the lawn, do not have a home, so there is no place to treat. They pose no threat unless handled or stepped on by bare feet.

Velvet ant. Photo by Johnny N. Dell, Bugwood.org

Information from "Yard Wasps" By Lee Townsend in the current edition of the Kentucky Pest News http://www.uky.edu/Ag/kpn/kpn_09/pn_090728.html

Turf - Grub Control With Beneficial Nematodes

The following is information on grub control in lawns using beneficial nematodes from the University of Maryland.

Non –Chemical Control of Grubs in Lawns

The interest in non-chemical control of white grubs in lawns is increasing. Japanese beetles are laying eggs in the soil in late July through early August. The newly hatching larvae will be very susceptible to control using beneficial nematodes. Nematodes are microscopic, non-segmented worms which occur naturally in soil all over the world. Beneficial nematodes attack soil dwelling insects and leave plants alone. These predators enter the host through body openings or by penetration of the body wall. Beneficial nematodes are considered safe and EPA has waived the registration requirements for application.

When Heterorhabditis bacteriophora (Hb) nematodes sense the temperature and carbon dioxide emissions of soil-borne insects, they move toward their prey and enter the pest through its body openings. The nematodes carry an associated symbiotic bacterium (Xenorhabdus species) that kills insects within 48 hours. The bacteria is harmless to humans and other organisms and cannot live freely in nature. Several generations of nematodes may live and breed within the dead pest before emerging and seeking more pests in the soil.

Heterorhabditis bacteriophora nematodes are a good choice for white grub control at this time of year. The key is that they need a lot of water to survive in turf areas. Irrigate the day of the application or apply during periods of rain. The lawn area must be keep moist for a couple of days after an application to keep the nematodes alive. Infected grubs become slimy and discolored and turn from white-beige to red-brown within 3 to 5 days after application. Nematodes leave the grub when they reach the infectious third stage to search for new larvae. The nematode population will slowly decrease when no new hosts are present.

Checking to Make Sure Nematodes Are Alive is Essential: It’s critical when using beneficial nematodes to check the population to make sure they are alive at application time. Draw off a small sample and examine the water with nematodes under a magnification of 20X. Live nematodes will be slightly curved and moving. Dead nematodes are still and straight as a board.

Information from Stanton Gill, University of Maryland http://www.ipmnet.umd.edu/09Jul24L.pdf

Greenhouse and Nursery - Mum Fertilization Revisited

With mum season in mid crop, I thought it would be good to do a reprint of recommended fertilizer programs for garden mums.

It is mid season and it’s a good time to revisit your fertilizer program. Mums are heavy feeders during the first few weeks. After flowers are formed, nutrient demand diminishes. Your fertilizer program and fertilizer selection should be based on irrigation water quality, so have your irrigation water tested if it hasn’t been done and conduct regular soil tests to monitor soil fertility.

There are several ways to fertilize mums. Some growers use 100% water soluble fertilizer through a drip system, some use 100% controlled-release fertilizer and some use a combination of water soluble and controlled-release.

1) 100% Water Soluble Fertilizer Using Drip Irrigation

After plants are established using 20-20-20 the first few weeks, switch to 200-250 ppm of 20-10-20 constant feed for 3-4 applications and then rotate to a calcium nitrate based fertilizer such as 15-0-15 for 1 application, then repeat. Once plants start to show color, reduce to 100 ppm constant feed.

2) Combination of Water Soluble Fertilizer and Low Rate of Controlled Release Fertilizer

Use 250 ppm of 20-20-20 at time of planting and constant feed for first two weeks then change to 20-10-20, 300 ppm once per week and use clear water from first color until sale.

Information from the June 5, 2008 edition of the New England Greenhouse Update. http://www.negreenhouseupdate.info/greenhouse_update/index.php

Landscape - Cedar-Quince Rust on Callery Pear

The following is information about a rust disease attacking Callery pears in Delaware.

CEDAR-QUINCE RUST

Samples of 'Bradford' Callery pear fruit and 'Redspire' have been diagnosed with cedar-quince rust. Since pear is in the same family as hawthorn and serviceberry--usual hosts of this rust, it stands to reason that pears could be infected as well. But, pear is a new host for this common disease. Infected fruit have the elongated white tube structures that protrude and turn orange with time. It is a superficial disease that only infects the fruit. So only the appearance of plants are affected not overall health. Since Bradford pears don't set lots of fruit anyway it may be hard to spot infected ones. Since there is concern over Bradford pears setting fruit and escaping into the landscape it will be interesting to learn if infected fruit can produce normal seed and germinate.

Information from Bob Mulrooney, Extension Plant Pathologist, UD

Landscape - Leaf Drop in Trees

The following is information on leaf drop in trees in midsummer. This is a common occurance during dry periods in many species. However, excessive premature leaf drop can be a cause for alarm indicating too much plant stress. the following is some additional information.

MID-SEASON LEAF DROP

When the leaves of large shade trees drop during mid-season, it typically causes alarm to concerned homeowners/clients. With the ground littered with spent foliage, the conclusion often is that “their favorite shade tree is dying!” Linden, birch, and sycamore trees are often most susceptible to mid-season leaf drop. In a majority of cases, this is a normal physiological growth habit for these species. The trees commonly drop foliage in mid-season in order to reduce leaf surface area and subsequent water loss. This leaf shedding ability is especially important during typical summer droughts or when water availability in soils is limited. Neither tree health nor tree growth is usually affected.

With this said, excessive premature leaf drop can be a sign that trees are undergoing too much stress. Plants with compromised root systems will be the most affected. If you suspect such a problem, examine the root system and take measures to reduce stress. This might include use of a tree spade to aerate compacted areas, additional watering where rooting is poor, or site corrections such as improving drainage (poor drainage can affect roots in wet periods leading to additional stress when soils dry out).

Some information from the Plant and Pest Advisory newsletter from Rutgers University, other from Gordon Johnson, Extension Horticulture Agent, UD.

Landscape and Nursery - Safari for Armored Scale Control

Safari, a systemic insecticide in the neonicotinoid class has much better action on armored scales than other products. The following is more information.

SAFARI (Dinotefuran)= New Armored Scale Control

Unlike Merit, the relatively new neonicotinoid insecticide named Safari (dinotefuran) has shown promise as an effective control against armored scales. Although both Safari and Merit (imidacloprid) have systemic capabilities with the same general mode of action, Safari is significantly more water-soluble. The high water solubility is thought to be the reason for the increased armored scale controls. Armored scales primarily feed by inserting their piercing-sucking mouthparts into parenchyma cells containing chlorophyll. Since Merit predominately moves through plants by vascular tissues (phloem and xylem), it does not readily enter into cells where armored scales feed. Consequently, Merit has not shown good efficacy against pests that feed within plant cells (typically less than 30-40% control). Recent University efficacy trials have shown dramatically improved results against armored scales with soil injection or drench applications of Safari insecticide. Although this material continues to be translocated by vascular tissues, it also appears to have the ability to permeate through cell walls and membranes. Some efficacy trials have shown controls exceeding 80%!

Information from Steven K. Rettke, Ornamental IPM Program Associate, Rutgers University in the recent edition of the Plant and Pest Advisory from Rutgers University http://njaes.rutgers.edu/pubs/plantandpestadvisory/2009/ln070909.pdf

Landscape - Lecanium Scales

Control opportunities exist now for controlling Lecanium scales. The following is more information.

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

Lecanium scale adults appear like little brown lumps grouped along branches. They feed on plant sap and leave a clear sticky substance (honeydew the scales' excrement) that gets on leaves, cars, etc. A black fungus called sooty mold often grows on it. European fruit lecanium has eggs (1000-3500/female) by May 9 and production occurs from 319-1328 GDD (median=654).

For Fletcher scale, eggs were noted by April 16 and continued from 171-1438 GDD (median=592). There is one generation per year. The crawler (hatchling nymph) stages look like tiny yellow-orange dots when tapped onto a white sheet of paper. Crawlers were seen in our area this past week and are later this year than the normal median crawler observations (between 850-900 GDD). The crawlers will migrate to the undersides of leaves/needles and spend the summer months there then migrate back to the branches to spend the fall and winter. They will resume growth, mate, and lay eggs the following spring.

The settled crawler stage is the best time to control lecanium scales. Many insecticidal products are registered for this purpose. Horticultural oil (1-2% v:v) applications work quite well. Occasionally, a re-application of oil is needed about 3 weeks after the initial application to ensure all crawlers have emerged and settled. Many naturally occurring parasites also control lecanium scales look for tiny holes in the adult scale's cover. Many predators like lady beetles also feed on lecanium scales. Insecticides sprayed well after crawlers have settled provide only limited effectiveness. Soil systemic insecticide applications of neonicotinoids such as imidacloprid (Merit) and Dinotefuran (Safari) work well against lecanium scales if applied in advance.

Information from Casey Sclar, IPM Coordinator, Longwood Gardens

Greenhouse - Bacterial Soft Rot on Poinsettias

As poinsettia season gets started with cuttings being rooted, greenhouse growers should watch out for bacterial soft rot. The following is more information.

We have had couple of reports of bacterial soft rot, Erwinia carotovora, showing up on poinsettias in greenhouses. E. carotovora is found everywhere and attacks stressed and weakened plants. Often the problem starts because of how the cuttings are handled. Most cuttings are produced offshore and when they arrive in the United States they are cooled by third party companies before shipment. The trucks they are shipped in are cooled to keep the poinsettia cuttings out of stress. If the cuttings are not kept cooled enough at any stage in this process then they become stressed. When the cuttings arrive at your greenhouse, reach into the box to check the temperature of the poinsettia cuttings. If cuttings feel warm, take them out and cool them down using ice packs, by misting them or by moving them into your cooler and lowering the temperature to 50°F. If you have to stick the cuttings right away, soaking them first will help reduce the temperature stress. Watering the oasis cubes or substrate before sticking also helps reduce stress on the cuttings. Do not heat the greenhouse at night for the first 2 - 3 nights. Greenhouse temperatures of 80-85°F/ 26-29°C during the day and 72°F/22°C at night are optimum for poinsettia propagation. Shading the greenhouse to 1500 - 2000 foot candles/16,140 - 21,520 lux will help reduce temperatures and stress on the cuttings. Remove all infected cuttings from the growing area. If you can get the plants past the first 4 to 5 days, you are usually “out of the woods” with this disease.

Reprinted from 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/09Jul24G.pdf

Turf - Weather Changes Mean Added Stress

Following a cool, wet, spring, turf will suffer challenges in the hot summer during dry periods. The following is an article on the subject from Rutgers University. Although it is focusing on golf courses and putting greens, the same effects will be seen on lawns and other turfgrass areas.

As the weather turns, so goes the turfgrass. Beautiful fall-like weather (I know it’s July) over the July fourth weekend really changed the dynamics on golf course putting greens in our region. Endless days of rain and overcast skies through May and June have been replaced with low humidity, high skies, cool breezes and moderate to high temperatures. Superintendents have been talking about super-saturated root zones and poor root mass for several weeks now and worrying about an abrupt change to summer heat. Those plants compromised by the wet spring were suddenly faced with a significant increase in transpiration demand. Over the last few weeks, we have seen plenty of poorly performing turfgrass on tough sites, but now we are starting to see plants that simply couldn’t keep up with the change in the weather. Putting green samples of both annual bluegrass and bentgrass are being submitted to the laboratory at a vigorous pace (25 this week). All of them have the same symptoms – slight thinning, poor growth and leaf tip scorch. The submissions came from Rehoboth Beach, Delaware to the south and out to the tip of Long Island to the north. Some samples, of course, look worse than others. Those where we find slight fungal insults - like Pythium root dysfunction or Curvularia fading out - or site related issues - like shade, compaction, or thatch - have more severe symptom expression. All of the samples; however, regardless of the source have the leaf tip scorch symptom in common. Pay close attention to the moisture needs of your turf areas moving forward and keep a careful eye towards stress related disease. There was a long period of wet and cloudy weather this spring and I think our turf may need to feel a little pain before it overcomes it.

Adapted from information by Richard J. Buckley, Director, Soil Testing and Plant Diagnostic
Services, Rutgers University http://njaes.rutgers.edu/pubs/plantandpestadvisory/2009/ln070909.pdf

Landscape and Turf - Welcome Rainfall

We got some welcome rain over the last 2 days. The following are rainfall totals across mid-state:

Dover = 1.03 inches
Bridgeville = 0.46 inches
Ellendale = 1.72 inches
Georgetown = 0.51 inches
Harrington = 0.08 inches
Kitts Hummock = 0.12 inches
Milford = 0.62 inches
Sandtown = 0.24 inches
Smyrna = 1.94 inches
Townsend = 0.07 inches (they did get 1.0 inches on 7/16)
Viola = 0.02 inches

As you can see, rainfall has been quite variable. Some areas are still dry, others have adequate moisture from rain. It is interesting to note that areas so close can recieve such different rainfall totals. Compare the Dover and Kitts Hummock locations within just a few miles of each other.

Gordon Johnson, Extension Agriculture Agent, UD, Kent County

Landscape - Current Pests

The following are some pests currently active in DE landscapes that you should watch for.

First generation fall webworm is being found on apple, crabapple and persimmon. Don't think it's the old tent caterpillar tents! Mechanical disruption of the web now will lessen the second generation.

The “Shothole” damage from Tortoise beetle feeding is prevalent on annuals (Ipomea ,etc.) and some perennials.

Rose midge is active this year again in many locations. Look for the “blighted” shoot tips on the terminal growth only.

Powdery mildew is all over crepe myrtle, lilacs, and other shrubs and flowering trees due to warm moist conditions combined with succulent new growth. Fungicides and sanitation may be required to prevent spread or overwintering.

Cicada Killer wasps are solitary wasps and are very unlikely to sting. Males fly at people, dogs, cats, other insects, etc. but are unable to sting. Females prefer to dig holes and sting cicadas. Treatments are rarely warranted.

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

Landscape and Turf - Wet then Dry, Bad Combination of Stresses

One of the worse combination of stresses on landscape plants and turf is a very wet spring followed by a drought in summer. The following is an article on the subject.

Drought Stress after a Wet Spring

A month ago we were very wet in many areas. Now, we are starting into drought stress conditions in parts of the state (as is common in DE summers). This combination of wet-dry can be extremely damaging to landscape plants and turf. In periods of excess moisture when soils are saturated, root growth often ceases due to lack of oxygen and some roots will die. There can also be increased incidence of root rots. Upon onset of hot, dry weather, plants with weakened root systems often will wilt prematurely and will have more severe stress. In addition, planting activities done in wet soils often creates added compaction and as soils dry out, plants will have a difficult time to root out. Cool season turf growth in cool wet springs is often excessive, especially with heavy spring nitrogen fertilizer. Turf in these conditions will increase shoot growth at the expense of root growth and will also deplete energy reserves. With the return of dry weather, this turf will undergo excessive stress. Trees and shrubs that experienced root damage in wet soils this spring will have additional stresses put on them during drought periods this summer. We are seeing premature leaf drop in many trees and shrubs at this time because of this double set of stresses (wet to dry).

Gordon Johnson, Extension Agriculture Agent, UD, Kent County

Pests of Stressed Plants

The following are some common pests of stressed plants. We are seeing drought stress in many parts of the state now.

Aphids and whiteflies are apparently drawnt o plants with yellowing foliage. Plantsunder stress often lose some of their chlorophyll and become yellowish in color. Yellow sticky cards are often hung in greenhouses to monitor for some of these pests.

Some species of caterpillars (not gypsy moth) are “samplers” when they feed. These caterpillars will sample individual leaves to determine if they contain plant defensive chemicals such as tannins or alkaloid toxins. If these toxins are contained within the leaves, the caterpillar may find it distasteful and move on to sample other leaves. A weakened plant unders tress may not have enough energy to produce these defensive chemicals and therefore, be more attractive for these caterpillars.

The greatest concern with stressed plants in the landscape is from borer infestations. The best examples of borer-prone plants are when drought conditions and high temperatures stress non-native plants. Pine bark beetles, bronze birch borers, and the two-lined chestnut borers are all encouraged when stressed tress are forced to “shutdown”their vascular systems (xylem& phloem tissues). When trees have low sap pressure, the borers can easily penetrate and cut through vascular tissue. Furthermore, trees with compromised vascular systems cannot readily transport defensive chemicals to areas invaded by borers.

Adapted from a presentation delivered by Dr. David Shetlar (The Ohio State University Extension)@ the RCE IPM Symposium, Nov. 1995

Landscape - Hot, Dry, Weather Pests

In some parts of down state Delaware, we have not had rain for 3 weeks and drought stress is evident. Hot and dry weather will favor certain pests. The following is more information.

Hot-Dry Weather Pests

It is well known that lacebugs reach their highest populations on plants located in sunny-dry locations. There are few predators in these areas,and the shallow rooted azalea is often under drought stress. Lacebugs typically thrive under these conditions.

Scale insects also generally will do better in hotdryweather primarily because the immatures are notknocked off the plants by raindrop “bombs.” Recently hatched scale crawlers are unprotected for several days as they move about the plant looking for a place to settle down. If rains do cause the crawlers to fall to the ground, it is unlikely they will be able to climb back up the plant before they die (their short-stubby legs do notwork very well). The timing of the rainfall to suppress the scale crawlers is critical, because they typically are active for only a few days. Once they settle down and insert their mouthparts into the plant tissue, they are less vulnerable to the raindrops.

Various leaf feeding beetles and caterpillars usually prefer hot-dry conditions, not because they may get knocked off the plants (they will often simply climb back up), but since they can be infected by fungal diseases if a lot of free moisture is present. For example, the Entomophagafungus that has been decimating most of the Gypsy Moth populations for more than a decade does an excellent job of keeping these caterpillar populations in check in cool, moist springs. However, when warm and dry springs occur, this pest typically returns to become a problem again in certain areas.

One of the most common of the warm season pests is the two-spotted spider mite. These pests thrive in very dry conditions, and they will reproduce more rapidly when it is warmer. Mites are vulnerable to being dislodged by heavy rains unless they are under protective leaf covering. Invariably, the worst spider mite populations within the landscape occur when plants are sited under over-hanging structures. In moist conditions, they also can be attacked by diseases but in dry weather, these diseases are not present. In the landscape, twospotted spider mites can have between 10 to 15 generations per year.

Adapted from an article by Steven K. Rettke, Ornamental IPM Program Associate, Rutgers University http://njaes.rutgers.edu/pubs/plantandpestadvisory/2008/ln0724.pdf