Inspector Findings in Kentucky

Transcription

1 Volume XIV, Issue VI Inspector Findings in Kentucky Office of the State Entomologist September Inside this issue: Thousand Cankers Disease Found in Tennessee Walnut Trees 2 Emerald Ash Borer Found in Tennessee 3 Hydrangea Cercospora Leaf Spot 4 Spruce Fungi Causing Needle Loss 5 Sawflies vs. Caterpillars 6 Kentucky Pest Survey Updates - Emerald Ash Borer, Gypsy Moth, LBAM 7 Sting Pain Index 8 Picture key: 1: thousand cankers, 2: emerald ash borer, 3: hydrangea leaf spot, 4: fall webworm, 5: cedar apple rust, 6: fall armyworm Pictures from and Kentucky Pest News

2 Page 2 Walnut Thousand Cankers Disease A Potential Threat to Kentucky By John Hartman and Lee Townsend Thousand Cankers Disease (TCD) is a recently recognized disease of walnuts (Juglans spp.). The disease results from the combined activity of the walnut twig beetle (Pityophthorus juglandis) and a canker producing fungus called Geosmithia. TCD has been active in the western United States for a decade but the cause was only recently described. TCD has been involved in several large scale dieoffs of walnut, particularly black walnut (Juglans nigra), growing in the west. Within the past few weeks, investigators in Tennessee have found the first case of TCD in an eastern state. This finding surely represents a threat to black walnut plantings in Kentucky. Disease vector. The walnut twig beetle (Pityophthorus juglandis), the vector of Thousand Cankers Disease (TCD), is native to New Mexico and Arizona where its distribution follows that of Arizona walnut, the likely native host. This 1.5 to 1.9 mm long yellow brown bark beetle aggressively attacks black walnut and carries the pathogens associated with TCD. Contrary to its common name, beetle attacks are not confined to twigs; tunneling is most commonly seen in branches greater than 0.7 inches in diameter and sometimes in trunks. The adult female begins to tunnel in walnut by early May to form a nuptial chamber with 1 or more radiating egg galleries. The small, white legless larvae develop below bark. A generation from egg to adult takes a little less than 2 months. However, adults can be present from mid-april through early October. Symptoms. Trees infected with the causal fungus first develop yellow leaves and eventually twig and branch decline and dieback (Figure 25). The fungus causes a canker, visible by peeling back the bark, corresponding to the activity of the insect vector in the branch or limb (Figure 26). When multiple cankers develop on the limbs (Figure 27) the vascular system is so disrupted that the limb dies. The combination of disease-causing fungus and insect vector is a lethal combination for walnuts. Figure 1 and 2. Dorsal and lateral views of the walnut twig beetle, the head is completely hidden from view, a characteristic of many bark beetles (Photo by J. LaBonte, Oregon Dept of Ag) Urban and parkland trees have been infected with TCD. Kentucky arborists, homeowners, and woodlot owners need to be alert to the possibility of TCD and report suspicious cases of walnut decline to local County Extension Agents and foresters.

3 Page 3 Emerald Ash Borer Discovered in East Tennessee By TN.gov Newsroom Plans underway to survey and restrict movement of ash material in Knox, Loudon counties NASHVILLE The Tennessee Department of Agriculture announced the discovery of emerald ash borer (EAB), the first detection of the destructive tree pest in the state. The discovery was made in late July at a truck stop in Knox County near the Loudon County line. We knew EAB could potentially reach Tennessee, and we re prepared to help slow the spread of the infestation and protect our forest resources. said state Agriculture Commissioner Ken Givens. We will be working closely with federal officials and other stakeholders to determine the extent of the infestation and to take steps to limit its spread. After receiving a report of a suspected find, state and federal officials collected specimens from infested logs for submission to the U.S. Department of Agriculture for positive identification. USDA confirmed the find late last week. EAB attacks only ash trees. It is believed to have been introduced into the Detroit, Mich. area 15 to 20 years ago on wood packing material from Asia. Since then, the destructive insect has been found also in Illinois, Indiana, Iowa, Kentucky, Maryland, Minnesota, Missouri, New York, Ohio, Pennsylvania, Virginia, West Virginia and Wisconsin. In response to the find, TDA plans to issue a quarantine in Knox and Loudon counties prohibiting the movement of firewood, ash nursery stock, ash timber and other material that can spread EAB. TDA plant inspectors and foresters will conduct a thorough survey of trees in the areas to assess the extent of the infestation. The USDA Animal and Plant Health Inspection Service is working closely with TDA in response and will likely issue a federal quarantine in the coming days in support of national efforts to control the spread of EAB. Typically, the Emerald Ash Borer beetles can kill an ash tree within three years of the initial infestation. Adults are dark green, one-half inch in length and one-eighth inch wide, and fly only from April until September, depending on the climate of the area. In Tennessee, most EAB adults would fly in May and June. Larvae spend the rest of the year beneath the bark of ash trees. When they emerge as adults, they leave D-shaped holes in the bark about one-eighth inch wide. The Tennessee Department of Agriculture Division of Forestry estimates that five million urban ash trees in Tennessee are potentially at risk from EAB. The risk represents an estimated value loss of $2 billion. There are an estimated 261 million ash trees on Tennessee public and private timberland potentially valued as high as $9 billion. TDA officials urge area residents and visitors to help prevent the spread of EAB: Don t transport firewood, even within Tennessee. Don t bring firewood along for camping trips. Buy the wood you need from a local source. Don t bring wood home with you. Don t buy or move firewood from outside the state. If someone comes to your door selling firewood, ask them about the source, and don t buy wood from outside the state. Watch for signs of infestation in your ash trees. If you suspect your ash tree could be infested with EAB, visit for an online symptoms checklist and report form or call TDA s Regulatory Services Division at

4 Page 4 Hydrangea Cercospora Leaf Spot is Active By John Hartman Cercospora leaf spot of hydrangea is being observed more often than usual this summer in home landscape plantings throughout Kentucky. This disease, caused by the fungus Cercospora hydrangeae, also has the potential to damage plants growing in the nursery. The common landscape hydrangeas, including bigleaf, oakleaf, panicle, and smooth-types are all susceptible. Although plants are not killed by leaf spot, it can cause premature defoliation which may reduce flowering and plant vigor. Cercospora leaf spot is favored by warm weather with frequent rain showers such as that experienced here this summer. Symptoms. Infected leaves in the lower part of the plant may first be observed in mid-summer with small circular purple spots scattered across them. As the purple spots enlarge, the centers of the spots turn tan or gray. The spots are usually about one-fourth inch in diameter and the fungus produces spores in their tan centers. Spores produced in the spots can be rain-splashed or wind-blown to other hydrangeas nearby to begin new infections. Heavily spotted leaves may turn light green or yellow and drop from the plant. These infected, fallen leaves can be an overwintering site for the fungus and a source for new disease the next year. During the growing season, disease development and spread are slowed significantly by extended periods of drought. Disease management. Provide good plant spacing so that air movement and sunlight penetration can dry the leaves quickly. Avoid use of overhead watering of the plants or water early in the morning so that leaves can dry off during daytime. Remove and destroy dead diseased leaves (when they are dry) to reduce disease spread. Clean out plant debris in winter to prevent overwintering of the fungus. Fungicide treatments are suggested only on valuable plants that incur noticeable damage every year. Fungicides containing active ingredients such as azoxystrobin, chlorothalonil, mancozeb, myclobutanil, or thiophanate-methyl are suitable for managing this disease. Fungicide applications would need to begin just before or just as spots are beginning to appear. Repeat applications may be needed.

5 Page 5 Spruce Fungi Causing Needle Loss By John Hartman During recent weeks, numerous samples of spruce twigs and branches shedding yellow or brown needles have been observed in the Plant Disease Diagnostic Laboratory and in several landscapes. Symptoms have included yellowing, browning and shedding of current and especially last year s needles resulting in twig and branch dieback. Normal needle drop. Spruce and fir trees typically retain their needles for several years. In most years, needle drop is hardly noticeable without careful examination of the inner branches where a few scattered needles may turn yellow and drop in late spring or early summer of their third year. Normal needle drop is a seasonal occurrence and can vary from tree to tree and from year to year. Sometimes these old, yellow needles can harbor saprophytic fungi, but these fungi are unlike the parasitic fungi that appear on younger needles. Two needle cast diseases. The fungi Rhizosphaera kalkhoffii and Stigmina lautti are the causes of needle cast being seen now on spruce trees in Kentucky. Rhizosphaera needle cast symptoms consist of yellowing first-year or older needles in summer which later turn brown and drop (Figure 30), perhaps 15 months after initial infection. Thus, needles dropping now could be the result of infections that occurred last summer, 2009 (a wet season here in Kentucky). Diseased needles contain fungal signs in the form of dark spherical pycnidia which typically emerge from the needle stomata and are thus lined up in rows (Figure 31). These rows of pycnidia protruding through the stomata can be seen with the aid of a hand lens, and are pretty diagnostic for this disease. Damage typically starts on the lower branches and moves up the tree. After 3 to 4 years of severe infection the lowest branches may begin to die. Colorado blue spruce, Picea pungens, is highly susceptible to this disease. White spruce, P. glauca, is intermediate in susceptibility and Norway spruce, P. abies, is relatively resistant. Trees that are stressed from drought, poor planting practices, or other factors are more likely to suffer from Rhizosphaera needle cast. Stigmina needle cast has also been observed on shedding spruce needles this year (Figure 32). Stigmina is associated with spruce needle symptoms and signs almost identical to those of Rhizosphaera. Stigmina produces dark spore-bearing structures in the needle stomata (Figure 33), but under a hand lens or a dissecting microscope, they appear bushy compared to the compact pycnidia of Rhizosphaera. Without some magnification, the two diseases appear to be very similar. Other causes of needle cast. Another spruce needle drop is caused by a newly identified fungus, Setomelanomma holmii. This needle drop disease has not been found in Kentucky as far as can be deter-

6 mined. Yellow, sickly needles can also result from an infestation of spruce spider mites. Although spider mites are found on spruce in Kentucky, they have not been observed as frequently as the Stigmina and Rhizosphaera needle casts this year. Improving the health of landscape spruce trees. Spruce health is enhanced by providing good growing conditions. Provide one inch of water per week during times of drought. Be sure the water is applied over the root zone and avoid getting the foliage wet. Sawflies Caterpillars that are Different By Lee Townsend Caterpillars are familiar leaf feeders on many landscape plants. However, a closer look can avert control problems if the damaging insects are sawflies larvae of plant feeding wasps instead of caterpillars - immature stages of butterflies and moths. It seems that sawflies have been more problematic than normal on deciduous trees and shrubs this year. Troubles usually come from species that attack conifers Mulch underneath the trees to retain moisture. Grass competes very well and can actually contribute to water stress on trees. Prune out diseased and dying branches (only under dry conditions) and take them away for burning or burial. Pruning tools should be sterilized with 70% alcohol between cuts. If needle cast disease has been diagnosed, a spring treatment with a chlorothalonil-based fungicide may provide protection. Timing of the treatment should coincide with needle emergence and be repeated as necessary until full needle emergence has occurred. The number of abdominal legs is the easiest characteristic to use. Sawflies have a pair of fleshy legs on each abdominal segment; caterpillars have four or fewer pairs. Also, sawflies have a single eyespot on each side of the head and sometime it is dark and distinct. The importance of this difference comes in selection of chemical control because Bt (Bacillus thuringiensis) products will control caterpillars but not sawflies. Pyrethroids (permethrin, etc) or carbamates (Sevin) will control sawflies. Avoid unnecessary trunk or branch injuries. Loostrife sawfly

7 Page 7 Pest Survey Updates for Kentucky Emerald Ash Borer Our trappers have started removing the purple traps that have been hanging in ash trees across the state since May. We will begin screening approximately 6000 traps as soon as we start getting them in. We should be done screening by the end of October, so any new infestations will be known by then. trees around the state. There were roughly 5000 traps placed this year mainly in the Louisville Lake Cumberland, Northern Kentucky, and Eastern Kentucky areas. We also trapped along the Mississippi River. The traps that caught suspicious moths are currently being looked at closer to determine whether any are gypsy moths for certain. If we find new locations outside of the current quarantine area, the area could expand which will effect commerce dealing with ash wood or firewood. If there are any adjustments being made to the quarantine, it may not necessarily be known by the end of October when we finish looking at the traps. Just be aware that changes could take place and it s best to stay watchful of any news as things are changing quite frequently with regard to EAB. The latest find in Tennessee was unexpected considering they weren t even part of the trapping program this year. All updates along with current quarantine and treatment information can be found on our website Gypsy Moth Light Brown Apple Moth (LBAM) In 2010 Kentucky set 350 small white LBAM traps throughout the state targeting high-risk areas that include nurseries, residential and urban landscaping, public parks, orchards, and vineyards. Some of you may have had traps placed in your facilities. Traps were set out in spring, and are being removed in the late summer/ fall. So far, there have not been any positive finds of LBAM in Kentucky. If you would like any further information about these surveys or pests, please visit our website at The gypsy moth trapping survey is concluding for the 2010 season. You may have noticed some of the red or green prism shaped traps attached to

8 Volume XIV, Issue VI Page 8 The Schmidt Sting Pain Index is a pain scale rating the relative pain caused by different Hymenopteran stings. It is mainly the work of Justin O. Schmidt, an entomologist at the Carl Hayden Bee Research Center. Schmidt has published a number of papers on the subject and claims to have been stung by the majority of stinging Hymenoptera. Stings are based on a scale of 0 (least painful) to 4 (most painful). 1.0 Sweat bee: Light, ephemeral, almost fruity. A tiny spark has singed a single hair on your arm. 1.2 Fire ant: Sharp, sudden, mildly alarming. Like walking across a shag carpet and reaching for the light switch. 1.8 Bullhorn acacia ant: A rare, piercing, elevated sort of pain. Someone has fired a staple into your cheek. 2.0 Bald-faced hornet: Rich, hearty, slightly crunchy. Similar to getting your hand mashed in a revolving door. 2.0 Yellowjacket: Hot and smoky, almost irreverent. Imagine W. C. Fields extinguishing a cigar on your tongue. 2.x Honey bee and European hornet: Like a match head that flips off and burns on your skin. 3.0 Red harvester ant: Bold and unrelenting. Somebody is using a drill to excavate your ingrown toenail. 3.0 Paper wasp: Caustic and burning. Distinctly bitter aftertaste. Like spilling a beaker of hydrochloric acid on a paper cut. 4.0 Pepsis wasp: Blinding, fierce, shockingly electric. A running hair drier has been dropped into your bubble bath Bullet ant: Pure, intense, brilliant pain. Like fire-walking over flaming charcoal with a 3-inch rusty nail in your heel. From Wikipedia University of Kentucky Department of Entomology Office of the State Entomologist S-225 Ag Science Ctr N Lexington, KY State Entomologist - John Obrycki, Ph.D Joe Collins: Emerald Ash Borer Coordinator, pest surveys & phytosanitary certificates Carl Harper: Slow-the-Spread gypsy moth trapping coordinator, web design & phytosanitary certificates Address service requested Katie Kittrell: EAB compliance inspections, pest surveys, nursery inspections, newsletter Janet Lensing, PhD: State Survey Coordinator Jennie Condra and Sarah Vanek: nursery inspections, pest surveys Phone: (859) Fax: (859) joe.collins@uky.edu carl.harper@uky.edu katie.kittrell@uky.edu janet.lensing@uky.edu