Anthracnose Disease Symptoms Appearing in Landscape Trees John Hartman, Extension Plant Pathologist, Univ. of Kentucky. Volume X, Issue III.

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1 Volume X, Issue III O F F I C E O F S T A T E E N T O M O L O G I S T June 2006 Pests susceptible to controlbased on degree day forecasts ( )=Degree day ranges Bagworms ( ) Birch leaf miner ( ) Bronze birch borer ( ) Euonymus scale several overlapping generations ( ) European elm scale ( ) European pine shoot moth ( ) Flat headed apple tree borer ( ) Fletcher scale ( ) Japanese beetle emergence ( ) Lecanium scale ( ) Lilac borer ( ) Taxus mealybug repeat applications necessary ( ) Peach tree borer ( ) 2-4 sprays during this period Round headed apple tree borer ( ) 3 applications at 3 wk intervals San Jose scale ( ) repeat applications necessary Two spotted spider mite ( ) Wooly apple aphid ( ) Gladiolus rust Left: woolly apple aphids; Top: peach tree borer damage note gummy resin oozing from larval tunnels under bark; Right: Asian ambrosia beetle frass tubes; Below: adult female peach tree borer Potato leafhopper Inside this issue: Gypsy Moth Traps Going Up Fungus Gnats Are Serious Pests Gladiolus Rust Found In The United States Pg 2 Pg 3 Pg 4 Woolly Apple Aphid Pg 5 Iron Chlorosis Pg 5 Degree Day Totals Pg 6 Anthracnose Disease Symptoms Appearing in Landscape Trees John Hartman, Extension Plant Pathologist, Univ. of Kentucky Cool, wet weather in spring favors the fungi that cause anthracnose diseases in landscape trees. Symptoms of infections that occurred during recent weeks are appearing in several tree species. Although anthracnose diseases are common this year on landscape trees and also on some fruit crops, they are not all caused by the same fungus. Each host plant has its own anthracnose fungus, so, for example, don t assume that anthracnose of sycamore or grape is a threat to nearby dogwoods. The incidence and severity of anthracnose diseases of landscape trees varies with the season, and this year, symptoms appear to be at moderate levels. Ash anthracnose. Brown blotches along leaflet edges have been visible for the past week or so on new ash foliage. Many of these infected leaflets will begin to drop soon and carpet the walks and lawns nearby. Ash anthracnose is not normally a threat to ash tree survival, however,

2 PAGE 2 INSPECTOR FINDINGS IN KENTUCKY VOLUME X, ISSUE III and the ash trees will simply put out a new set of leaves. The ash anthracnose fungus is a species of Discula. Dogwood anthracnose. Caused by the fungus Discula destructiva, dogwood anthracnose is appearing this spring in many Kentucky flowering dogwoods (Cornus florida). Dogwood anthracnose causes leaf spots, leaf blight, and lower branch dieback and is most commonly observed in forested regions where native understory dogwood trees are threatened. This spring, anthracnose is also present in landscape trees, especially those growing in shaded locations. Maple anthracnose. Symptoms can range from leaf spots to shoot blight and shoot cankers. Maple anthracnose may be caused by Discula sp. or by Kabatiella apocrypta. Leaf spots with brown, somewhat angular symptoms associated with Kabatiella are being observed most commonly now. There is considerable variation in maple susceptibility to anthracnose. In some cases, sugar maple leaf spotting may be heavy on one tree while the adjacent tree is barely affected. Oak anthracnose. This disease is less common here and is caused by the fungus Apiognomonia quercina. Sycamore anthracnose. Anthracnose symptoms have become noticeable on sycamore in the past week. On infected green, expanding leaves, look for irregular dark, necrotic blotching centered along the leaf veins or leaf edges. These dark blotches may turn a tan color as the diseased areas of the leaves dry out. In the same trees, tips of young shoots with newly expanding leaves are wilting and dying because of twig or shoot infection. With continued rainy weather, the disease should continue to spread in the foliage. Symptoms are not as severe as we see some years when trees are heavily defoliated by now. As the weather gets warmer and drier, sycamores normally put out new, healthy foliage. However, the legacy of crooked branches (because lateral shoots take over when terminals are killed by anthracnose) and multiple shoots arising from the base of a killed branch may still be visible many years later. Sycamore anthracnose is caused by the fungus Apiognomonia veneta, and the fungus attacks both sycamore and London plane. Kentucky growers and gardeners should know how to grow and maintain healthy landscape trees. For most trees, anthracnose disease is not lethal, but it can be for dogwoods. Good growing practices are important in reducing the effects of anthracnose and in preventing loss of dogwoods from anthracnose. Consider the following: *Rake up and compost fallen leaves. Leaves can be a source of inoculum. *Prune out and destroy dead twigs and branches, because for many of the anthracnose fungi, branches harbor fungal inoculum. Although it is difficult to prune large trees, small trees are at greater risk, so prune out dead twigs and branches from them. For dogwoods, pruning out dead branches and water sprouts is especially important where anthracnose might be a threat. *Avoid unnecessary wounding and avoid construction or other activities which could injure the roots or the branches. *Provide mulch as needed. Maintain a 2-3 inch layer of mulch over the root zone of the tree (but not against the trunk) to help maintain soil moisture and to protect trees from lawnmower injury. *Protect trees from drought by watering at least once a week during dry periods. Do not use overhead sprinklers for watering; wet foliage favors infection. *Do not transplant dogwood trees from the wild. Purchase healthy trees from a reputable nursery. *Anthracnose is favored by a moist environment. Select a planting site with a sunny eastern exposure to promote rapid foliage drying early in the day. *Diagnose and treat insect and disease problems appropriately. *Plant disease resistant dogwoods such as C. florida Appalachian Spring or oriental dogwoods (Cornus kousa) for high risk sites such as those with heavy shade and nearby diseased trees. *Although most anthracnose diseases can be controlled using fungicides, the attempt is usually more costly than the benefit. Dogwoods which are threatened by anthracnose may benefit from early spring fungicide applications. Gypsy Moth Traps Going Up As you travel throughout Kentucky this summer, you may notice some green or brown colored triangular traps on the sides of trees. These traps are used by the University of Kentucky Entomology Department, USDA and the Kentucky Division of Forestry to detect Gypsy moths within the state. This year nearly 10,000 traps will be placed in 102 counties. These traps contain a pheromone lure which attracts the male gypsy moths. The pheromone is a mimic of the natural pheromone that virgin female moths use to attract males. Under ideal conditions, male gypsy moths are able to detect the pheromone at distances up to one mile. As the male moths fly around they detect the scent of the pheromone with their antennae. They will then fly towards the source and try to mate with the female. However, in the case of the artificial pheromone, as the moths fly toward the scent they fly into a trap and then become entangled on the sticky sides of the trap.

3 PAGE 3 INSPECTOR FINDINGS IN KENTUCKY VOLUME X, ISSUE III Fungus Gnats Are Serious Pests Leanne Pundt, Extension Educator & Greenhouse IPM Coordinator, Commercial Horticulture, Univ. of Connecticut Fungus gnats were once thought to be a nuisance pest only in the greenhouse. However, as fungus gnats were shown to cause direct feeding damage to crops, they are now considered a serious pest. Identification Fungus gnats and shoreflies both thrive in the damp, moist greenhouse environment. Correct identification is needed because management tactics vary according to the insect present. Adult fungus gnats are small (1/8 inch long), mosquito-like insects, with long legs and antennae. Their two wings are delicate and clear with an Y-shaped vein in the wing pattern. Adults tend to fly in a zigzag pattern and are attracted to fungi so might be observed near plants with Botrytis sporulation. Females lay their eggs nearby so the larvae have access to a fungal food source. Fungus gnat larvae are small, translucent to white in color with a distinctive black head capsule. Shore fly adults resemble a small housefly with stockier bodies, plus shorter legs and antennae than fungus gnats. Shore fly larvae are white, wedge-shaped and do not have a distinctive head capsule. Larvae may be found near algae, a primary food source. They do not feed on plants. Fungus Gnat Damage Fungus gnats are most damaging to seedlings, cuttings and young plants. As fungus gnat larvae feeding on tender young roots, this feeding injury provides an entryway for pathogens. Larvae also feed on the developing callus of direct stuck cuttings, delaying rooting. Fungus gnats are general feeders. Plants with succulent stems, such as geraniums, sedum, coleus and poinsettias, are especially prone to injury and suffer serious losses. As the young feeder roots and stems are damaged, affected plants wilt. Leaves may turn yellow and drop. In laboratory studies, adult fungus gnats carried spores of Pythium, Botrytis, Verticillium, Fusarium and Thielaviopsis as they moved from plant to plant. Spores have also been found in their droppings. It is unclear how important this disease transmission is in commercial greenhouses. Life Cycle The fungus gnat's life cycle from egg to adult may be completed in as little as three to four weeks depending on temperature. Eggs are laid in cracks and crevices in the media surface and mature in four to six days. Fungus gnat larvae feed and develop for about two weeks at 72 o F. Pupation occurs in the soil. After four to five days, adults emerge. Overlapping and continuous generations make control difficult. Cultural Controls Adults are attracted to newly planted crops, making it important to thoroughly clean the greenhouse before introducing new crops. Dry, level, weed-free, well-drained floors help eliminate breeding areas. Keeping compost piles away from the greenhouse and cleaning up any spilled media on the floor also helps eliminate breeding areas. Inspect incoming plugs for fungus gnat larvae or their feeding damage. Recent studies have shown that fungus gnats may be introduced into a greenhouse from soilless media or rooted plant plugs. Adults are attracted to mixes with high microbial activity, or with high amounts of peat moss or hardwood bark. Avoid using mixes with immature composts less than one year old. However, no potting mix is completely immune to fungus gnat infestations. Adult females prefer to lay their eggs in protected, humid crevices in the media. How the media is handled and stored may be more important than the type of mix used. If the mix is stored outside and stays moist, it may support more fungus gnat activity. Tears or openings in the bags enable resident fungus gnat populations to gain entry into the media bags. Store the media so that it stays dry. Monitoring Monitoring is especially crucial if you are planning on targeting biological controls or insect growth regulators against the fungus gnat larvae. Inspect incoming plugs for fungus gnat larvae or their damage. Place yellow sticky cards in samples of growing media to monitor for any emerged adults. Yellow sticky cards, placed horizontally at the soil surface, can be used to detect adults. Check and change the cards weekly to determine population trends. Use potato plugs (at least one inch in diameter) placed on the soil surface to monitor for larvae. When using potato plugs, place the plug so there is contact with the media to ensure that the potato plug does not dry out. To look for larvae, first check the growing media under the plug and then the surface of the potato itself. Check the potato plugs after 48 hours. Be sure to mark the pots where you placed the potato plugs, so you can easily find them! If not removed, potato chunks can "melt out," sprout or be fed upon by mice. For smaller cuttings or plugs, potato slices, resembling a French fry can be placed in the media. Biological Controls Bacillus thuringiensis var. israelensis, sold under the trade name of Gnatrol, is most effective against the young first instar larvae. The bacteria must be ingested by the larva, after which a toxic protein crystal is released into the insect's gut. Larvae stop feeding and die. Gnatrol is only toxic to larvae for two days. Repeat applications, i.e. two or three applications at high rates, may be needed to provide effective control. Steinernema feltiae(scanmask, NemaShield, Nemasys or Entonem) are beneficial, insect killing nematodes that are also applied as a drench treatment against fungus gnat larvae. After entering the target insect through various openings, the nematodes multiply within

4 VOLUME X, ISSUE III the host and release a bacterium whose toxin kills the larvae. These beneficial nematodes reproduce within the fungus gnat larvae; exit the dead body and search for new hosts to infect. Fungus gnat larvae are killed in one to two days. Early treatments of rooted plant plugs and cuttings with beneficial nematodes provide better control than later treatments. A small, soil-dwelling predatory mite, Hypoaspis miles, feeds on fungus gnat larvae. It is shipped in a vermiculite/peat carrier with all stages of the predatory mites. The vermiculite/peat carrier can be distributed over the media surface, especially when pots are placed close together. These predatory mites are best used when fungus gnat populations are low and are compatible with Gnatrol and S. feltiae. Insect Growth Regulators Insect growth regulators (IGR s) are most effective against the young developing larvae and will have no Gladiolus Rust Found In The United States John Hartman, Extension Plant Pathologist, University of Kentucky The following information is adapted from communications received recently from the USDA Animal Plant Health Inspection Service - Plant Protection and Quarantine and the National Plant Diagnostic Network. Gladiolus rust, caused by the fungus Uromyces transversalis, is of plant quarantine importance in Europe and the United States. This fungus primarily attacks hybrid cultivars of gladiolus grown for flower production and could have significant impact if it became established or was transported into greenhouses or nurseries. This rust is apparently indigenous to eastern and southern Africa. It has also been reported from other parts of Africa, Europe, South America, Australia, and New Zealand, and has recently been intercepted from Mexico. The fungus name, U. transversalis is derived from the transverse arrangement of pustules INSPECTOR FINDINGS IN KENTUCKY direct activity against adults. Commercially available IGR's include Adept, Azatin XL, Aza-Direct, Ornazin, Citation, Distance and Enstar II. Adept (difluorobenzamide) is an insect growth regulator that is labeled for fungus gnat and shore fly larvae. In 1998, New England growers reported marginal leaf burn on poinsettia crops. The injury seemed to be rate related, especially if the volume of drench applied exceeded the recommended labeled rates. Injury symptoms did not occur until four to six weeks after the application. Please note that the Adept label has been changed. The label now reads:" Warning: Exceeding label rates, volumes or number of applications of Adept can cause serious foliar injury to crops, particularly to poinsettias, hibiscus and Reiger Begonias. Do not apply Adept to poinsettias, hibiscus and Reiger Begonia. No sensitivity has been observed with other bedding or pot crops including plugs and liners, however, tests should be that develop across the width of the leaves, as compared to most rusts on monocots whose pustules burst through longitudinally along the veins of the leaf. Gladiolus rust was found in April, 2006 in Hawaii on leaves of cut gladiolus flowers coming from Florida. Dr. Mary Palm, USDA National Mycologist, confirmed this initial identification. Trace-back of the interception in Hawaii indicated that the rust-infected gladiolus originated from a gladiolus production farm located in Florida. PPQ authorities and Florida Department of Plant Industries officials found rustinfected gladiolus plants in much of a grower facility. This is the first find of gladiolus rust in Florida. A group of quarantine experts is being convened to provide technical support for mitigation and eradication of the rust. In addition, local survey and trace-back activities are underway. Kentucky nursery and greenhouse flower growers will want to inspect gladiolus plants for rust diseases. conducted to insure safety to any crop before extensive use." PAGE 4 Other Treatment Options DuraGuard ME is a microencapsulated product that may be used for both larvae and adults. The neonictotindoids Safari (dinotefurnon), Flagship (thiamethoxam), Marathon (imidacloprid) and Tristar (acetamiprid) are labeled for fungus gnat larvae. Pylon has contact and stomach activity against fungus gnat larvae. Treatments Against Adults For well-established populations, applications of an adulticide may be of benefit. Some insecticides for use against fungus gnat adults include Talstar Flowable, Attain TR, Decathlon 2O WP, Astro, 1300 Orthene TR, 1100 Pyrethrum TR, Duraplex TR, and Tame/Orthene TR. Contact materials such as insecticidal soap, ultra-fine oil, and synergy super fine spray oil emulsion are also labeled for fungus gnat adults. Be especially vigilant for rust on gladiolus plants being shipped to the nursery or greenhouse. Rusts generally are recognized by the formation of leaf pustules producing orange spores. Pustules can also form on the inflorescence and flower spike of gladiolus. Gladiolus rust disease has resulted in 100% losses and has made production of gladiolus for cut flowers almost impossible without fungicide use in parts of Africa. The initial gladiolus rust pest alert is posted on the internet at: oprdetail.cfm?oprid=198 For more information and photographs of gladiolus rust on the internet, consult the following (long) URL: taxadescriptions/factsheets/ index.cfmthisapp= Uromycestransversalis For information on quarantines and rust diseases of ornamental plants on the internet, consult the following: feature/quarantine/

5 PAGE 5 INSPECTOR FINDINGS IN KENTUCKY VOLUME X, ISSUE III Woolly Apple Aphid Ric Bessin, Extension Entomologist, University of Kentucky The woolly apple aphid differs from other apple aphids in appearance, life cycle, and the type of damage inflicted. A colony appears as a cottony mass generally clustered in wounds and pruning scars on the trunk and branches of the tree. The aphids themselves are purplish in color surrounded by white, cottony, thread-like secretions. Woolly apple aphid is a sucking insect pest that weakens the tree by feeding on limbs and roots. It gets its name from the woolly appearance of its colonies. Long strands of white wax are produced that help to protect the colony of purple aphids from predators and pesticide sprays. Woolly apple aphid is a serious pest of apples, particularly young trees. It is also found on elm, pear, quince, hawthorn, mountain ash, and cotoneaster. Colonies form at wound sites on trunks, limbs, and twigs, where they feed on tender bark. Pruning and hail damage can create the wound sites for attack by this pest. Egg-laying wounds by the periodical cicada are ideal sites for infestation. As populations grow, aphids are commonly found on water sprouts in the center of the tree. The tree will begin to swell and form galls at the feeding sites. As the number of aphids on the above ground portion of the tree increase, many work their way down to the roots and trunk below ground surface. It is the feeding on the roots that produces the greatest Iron Chlorosis David J. Robson, Extension Educator, Horticulture, Univ. of Illinois Extension When a person doesn't get enough iron, we say they have iron poor blood. When plants don't get the necessary levels of iron, the condition could be referred to as iron poor chlorophyll or more correctly iron chlorosis. Iron, an important component of chlorophyll, must be available to plants in adequate damage. Mature trees usually suffer little damage from the root infestations, but the root infestations are very damaging to young trees. Control of these aphids is very difficult when they attack the roots. Yellowish foliage is a sign that woolly apple aphid may be infesting roots. The root systems of nursery stock can be damaged, and severe root infestations can stunt or kill young trees. Infested trees often have short fibrous roots, which predisposes them to being easily uprooted. Swollen galls also form on roots; galls increase in size from year to year and are sites where fungi can attack. Aphid feeding on the root systems also disrupts the nutrient balance of root tissue, which can affect growth of other parts of the tree. Trees can have above-ground infestations of woolly apple aphid but no root infestations. Rootstocks vary in susceptibility to woolly apple aphid and susceptible rootstocks will form galls around the infestation sites. Use M111 or M106 if woolly apple aphid is a serious problem. Rootstocks appearing more susceptible to woolly apple aphid infestation include B9, M9, M26 and the P series. During the summer, repeated woolly apple aphids generations of wingless individuals are produced. In the fall, winged individuals are produced which fly to search for elms on which to lay overwintering eggs, while some wingless forms may remain on both above and below ground parts of the apple tree throughout the winter. amounts to keep leaves green and producing food. If iron becomes unavailable, leaves begin to yellow. Iron is taken up by plants only as an iron ion and is available in this form only when the soil ph is between 5.0 and 6.5. If the soil ph is low (acid) or above (alkaline), iron becomes unavailable for plant uptake. A deficiency of available iron is often aggravated by plants under stress from poor root aeration or soil drainage and restricted root growth. Woolly apple aphid colonies produce honeydew, which results in development of black sooty mold. The wax and the honeydew are bothersome to pickers when it brushes off the tree and onto clothing of pickers. Monitoring It is relatively easy to find where the colonies have formed. When monitoring for woolly apple aphid, examine four pruning scars on each of 5 scaffold limbs per tree. Carefully examine woolly apple aphid colonies to determine if live aphids are present. Predators, such as lady beetles, Syrphid fly larvae, and lacewing larvae can completely destroy the colony, but the waxy residue will remain. When examining colonies, blow hard on the branch to remove the waxy filaments to reveal live aphids. Treatments for woolly apple aphid are recommended when 10% of the pruning scars are infested with live colonies. Control There are few insecticides specifically labeled for control of woolly apple aphid. Diazinon, Thiodan and Cygon are recommended for control of above-ground infestations. Insecticidal soap may also be used. For effective control, apply insecticide using a high volume application throughout canopy when aphids are young and beginning to move up into the trees. This may be occur anytime from late-spring to mid-summer. Check plants two weeks after application to determine if a second application is necessary. There are no insecticides to control root infestations on bearing apple trees. Over 250 species of plants are susceptible to iron chlorosis. The plants most commonly affected include blueberry, azalea, hydrangea, silver and sugar maples, pin oaks and rhododendron. The lack of available iron produces a variety of symptoms on trees and shrubs from a partial or complete yellowing (chlorosis) of young leaves to poor growth or the death of the plant. Symptoms may include the death of leaves, premature leaf

6 drop, a stunting and dieback of twigs and branches, and the failure of ornamentals to produce flowers or fruit. Occasionally, only part of a tree or shrub will show symptoms. Chlorosis, the most common symptom, is characterized by a pale coloration of interveinal leaf tissues, yellowish green to golden yellow. The network of veins remains green. If severe, the leaves may be dwarfed, turn ivory colored and appear scorched along the margins; or brown spots may develop between the veins. Such leaves eventually curl, wither, and drop prematurely. Trees under the stress of a high iron deficiency may have severely stunted or dead terminal twigs and branches, while the lower and older branches appear normal. Iron chlorosis can be confused with zinc and manganese deficiencies. Iron chlorosis can often be differentiated because the chlorosis appears first on the younger or terminal leaves, spreading later to the lower parts of the plant. Zinc and manganese deficiencies appear first on the older, basal leaves. Iron chlorosis can be controlled when plants are supplied with available iron. The iron may be sprayed on to the chlorotic foliage, introduced into the trunk, or added to the soil. The most lasting results are obtained through treating the soil. Reminder: Nursery license renewals are due June 16, 2006 Degree Day Totals through May 26, 2006 Bardstown 705 Bowling Green 898 Covington 577 Henderson 788 Huntington WV 766 Lexington 622 London 751 Louisville 689 Mayfield 735 Paducah 999 Princeton 968 Quicksand 751 Somerset 659 Degree Day Totals through May 27, 2005 Bardstown 688 Bowling Green 761 Covington 569 Henderson 755 Huntington WV 709 Lexington 631 London 683 Louisville 681 Mayfield 703 Paducah 836 Princeton 855 Quicksand 712 Somerset 677 S-225 Agricultural Science Center - North Lexington, Kentucky OFFICE OF STATE ENTOMOLOGIST We re on the web! State Entomologist John Obrycki, Ph.D Joe Collins: nursery inspections, newsletter, pest surveys & phytosanitary certificates Carl Harper: Slow-the-Spread gypsy moth trapping coordinator, nursery inspections, web design & phytosanitary certificates Janet Lensing: nursery inspections Phone: (859) Fax: (859) joe.collins@uky.edu carl.harper@uky.edu jrlens2@uky.edu