JULY 2015 OFFICE OF THE STATE ENTOMOLOGIST VOLUME XVIII, ISSUE IV COTTONY CAMELIA SCALE PAGE 2 INSPECTOR FINDINGS

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1 COTTONY CAMELIA SCALE PAGE 2 DOGWOOD POWDERY MILDEW PAGE 4 DOGWOOD SAWFLY PAGE 12 INSPECTOR FINDINGS Skeletonized oak leaf photo by Lee Townsend University of Kentucky Department of Entomology Office of the State Entomologist S-225 Ag Science Ctr N Lexington, KY Phone: (859) Fax: (859) !1

2 Cottony Camellia Scale by Lee Townsend, Extension Entomologist Cottony camellia scale is a sap-feeding insect that infests camellia, holly, yew, euonymus, and maple. Infested plants usually have a significant amount of black sooty mold growing on the sugary honeydew or liquid waste produced by these insects. Heavy infestations may cause leaves to turn light green in spring (Figure 1). The easily overlooked flat females live on undersides of leaves and are about 1/8 inch long, oval, and yellowish-tan with a brown margin. However, they produce very noticeable elongate white cottony sacs containing several hundred eggs (Figures 2).! Figure 1. Cottony camellia scale causes sparse foliage and yellowed leaves on this holly, and white egg sacs of cottony scale are present. (Photo: A. Heisdorffer)!2

3 ! Figure 2. White egg sacs of cottony Camellia scale (400 to 600 eggs per sac) on holly leaves. (Photo A. Heisdorffer) Management Alternatives Light infestations often can be managed by hand-picking and destroying infested leaves. Remove any cottony egg masses found on leaves in mid- to late May. Prune and destroy more heavily infested leaves and branches when practical. Crawlers hatch from eggs from late May through June. They settle on the undersides of the leaves to feed on sap and grow through winter. This stage is most vulnerable to control with insecticides or insecticidal soap. Use of insecticidal soap helps to preserve natural enemies of the scale. Use a superior dormant oil spray during winter to kill overwintering scales on foliage.!3

4 Dramatic Dogwood Symptoms Draw Attention By Julie Beale, Plant Disease Diagnostician For the past week, questions of what s going on with the dogwoods? have inundated county Extension offices, but until yesterday only a few of these samples had been submitted to the UK Plant Disease Diagnostic Laboratory (PDDL) for diagnosis. Concerned homeowners reported symptoms ranging in severity from mild leaf scorch to sudden, alarming defoliation. Other symptoms included leaf distortion, marginal burn, brown blotches, and a white, powdery coating on leaves. The dozen or so dogwood samples I examined in the PDDL yesterday and another dozen I surveyed during a neighborhood walk yesterday evening had two common foliar diseases: powdery mildew and anthracnose. Both of these diseases are caused by fungi that are quite hostspecific, meaning the powdery mildew fungus that infects dogwood can spread to nearby dogwoods, but does not infect other, unrelated plants. Likewise, the anthracnose fungus on dogwoods is different from the anthracnose of other shade trees, even though symptoms are similar. Dogwood Powdery Mildew On dogwood, young expanding leaves infected with powdery mildew are often crinkled and distorted and fail to reach a normal size. In addition to white, powdery fungal growth easily visible on leaves, foliage often becomes scorched, either along the leaf margins or in patches on the leaf blade, sometimes even before the powdery growth is obvious. Later in summer, heavily infected trees may appear droughtstressed due to excessive moisture loss through the leaves. Powdery mildew was clearly visible on all of yesterday s dogwood samples as well as all the neighborhood trees I surveyed (Figure 1). Figure 1. White fungal growth (left) as well as scorching may be apparent on dogwood leaves with powdery mildew. (Photo: Julie Beale, UK)!4

5 High humidity favors powdery mildew, therefore, cycles of wet, followed by hot, drier weather this spring promoted exceptional early development of powdery mildew. Dramatic scorching occurred in some trees when infected leaves were exposed to sudden, intense heat at the end of May. Dogwood Anthracnose Some of the browning and leaf drop reported recently, however, did not fit the typical symptoms associated with powdery mildew. Close examination of samples confirmed what I suspected: dogwood anthracnose disease, caused by the fungus Discula destructiva, was present, too, on about half of the samples in the mini-survey (Figures 2 and 3). Figure 2. Symptoms of anthracnose and powdery mildew together. (Photo: Julie Beale, UK)!5

6 Figure 3. Close-up of glossy, brown bumps within necrotic leaf tissue, fungal structures of Discula destructiva; also note fine, white webbing of the powdery mildew fungus. (Photo: Julie Beale, UK) Symptoms of anthracnose include blighting/blackening and collapse of leaves, and/or large, irregular brown patches, often (but not always) with a dark purple border. These symptoms tend to be worse in the lower canopy. Other shade trees such as ash or maple readily drop anthracnose-infected leaves, but such extensive leaf drop on dogwood is less common. (Only a few trees in my survey were defoliating, but homeowners have reported dramatic leaf drop in some landscapes). Cool, rainy weather during leaf expansion favors anthracnose, thus, weather patterns this spring also promoted anthracnose infections. Management and Prognosis Returning to the current dogwood drama, at this point the anthracnose disease must run its course. The window of treatment with fungicides is past once symptoms are apparent, and treating large trees can be difficult and expensive. Raking up and removing fallen leaves will reduce disease risk next!6

7 year. However, small twig tips may harbor the anthracnose fungus, increasing the risk of disease on a given tree in subsequent years, providing weather conditions are cool and wet during leaf expansion. Since humidity favors powdery mildew, we are likely facing severe dogwood powdery mildew situations all season. Leaves may become more scorched as the summer progresses, and although powdery mildew is not considered a lethal disease, reduced leaf function may weaken trees over time, leaving them vulnerable to borer infestation and opportunistic diseases. Mulching and irrigation directed at the root zone will reduce moisture stress to infected trees. For more information on dogwood anthracnose and powdery mildew, refer to UK Extension Plant Pathology factsheets: Dogwood Anthracnose (PPFS-OR-W-6) Dogwood Powdery Mildew (PPFS-OR-W-13 What To Look For:!7

8 Emerald Ash Borer in Three New Counties Joe Collins, Senior Nursery Inspector in the Office of the State Entomologist, captured an emerald ash borer (EAB) in a trap placed at Fort Boonesboro; this is the first discovery of this insect in Madison County. Jessica Cole, Mercer County Extension Horticulture Agent, reported a finding from Mercer County, as well. An adult was also captured on a trap in Harlan County. The map depicts the known distribution of EAB in Kentucky at this time. Infestation levels and ash mortality are: high (red), moderate (yellow), low (green), and undetected (white). EAB adults should still be active but flight should be declining. Females live about 3 weeks; each lays 30 to 60 eggs, which hatch in 2 to 3 weeks. Newly hatched larvae tunnel through outer bark into the phloem where their galleries disrupt water and nutrient transport. Feeding generally ends in October. Larvae then pass the winter in cells they create in the sapwood or outer bark.!8

9 Nightmare On Oak Street By Lee Townsend, Extension Entomologist Oak Leaf Skeletonizer A leaf attacked by oak leaf skeletonizer (OLS) caterpillars is reduced to a veiny skeleton held in place by thin tissue of the upper leaf surface (Figure 1). Figure 1. Skeletonized oak leaf showing areas containing only veins and the translucent upper leaf surface. (Photo: Lee Townsend, UK) Skull-like empty head capsules littering the lower leaf surface bear mute testimony to molt of these small caterpillars as they grow. Accumulations of black pepper-like waste pellets cling to the silk shrouds (Figure 2) under which the ghostly pale caterpillars retreat to molt or to pupate.!9

10 ! Figure 2. Oak leaf skeletonizer caterpillar with black frass pellets (Photo: Lee Townsend, UK)! Figure 3. Individual feeding sites of oak leaf skeletonizer with silk pads and frass. (Photo: Lee Towsend, UK)!10

11 ! OLS caterpillars are pale yellow green and about ¼-inch long when fully grown. When disturbed, they drop from leaves on silken threads. OLS occurs over much of the eastern U.S., but its activity usually goes unnoticed. Most of the time populations are held in check by weather or natural enemies. A recent sample from south central Kentucky showed extensive damage by this species and could mean population levels are up in other locations. Feeding by the first of two generations is nearing completion, but a second generation occurs during July and August. Management Control of this insect may be warranted on small, newly established landscape trees, but several consecutive defoliations would be necessary to affect the health of larger, established trees. General tree and shrub insecticides that list caterpillars on the label can be used if control is necessary and practical. Support tree health by watering if needed and fertilizing as recommended. Oak Slug Sawfly Larvae Oak slug sawfly larvae cause similar skeletonization of leaves at about the same times that the two OLS generations are present, but there are some noticeable differences. Slug sawflies chew their way across the underside of leaves in a shoulder to shoulder wave (Figure 4) Figure 4. Line of oak slug sawflies chewing their way across a leaf. (Photo: Lee Townsend, UK) while OLS caterpillars feed in isolated patches that can coalesce. In addition, there are no silk pads on the undersurface of infested leaves where sawflies have fed. This can be an important distinction because sawflies are larvae of plant feeding wasps and are not affected by Bt sprays that might be selected for caterpillar control. Infestations usually are confined to scattered leaves.!11

12 ! Dogwood Sawflies By Lee Townsend, Extension Entomologist As with many plant-feeding insects, the dogwood sawfly is one of those pests that rarely draws much attention but occasionally can be very destructive. A report of damage early this week provides a good opportunity to review this interesting and variable group. Individual sawflies have normal appetites for insects their size; it is the group feeding that can cause problems. Sawfly eggs are laid in loose clusters in leaf tissue. Early feeding damage caused by the small caterpillar-like insects is easy to overlook. However, leaf consumption increases dramatically as they grow, so defoliation can occur almost overnight. In addition to the enhanced impact of group feeding, the appearance of these larvae changes as they develop. It can appear that more than one pest species is active. Figure 1. An early stage of the dogwood sawfly sports a white waxy covering. In a few days these larvae will be yellow and black. (Photo: K. Cowherd) Since dogwood sawfly larvae tend to occur in groups, it is often convenient to remove and destroy a few leaves to end the infestation. There is only one generation each year. John Obrycki, Ph.D: State Entomologist Joe Collins: joe.collins@uky.edu Pest surveys & nursery licenses Carl Harper: carl.harper@uky.edu Slow-the-Spread gypsy moth trapping coordinator, phytosanitary certificates Katie Joya: katie.joya@uky.edu Pest surveys, nursery inspections, newsletter editor Jennie Condra: jennie.condra@uky.edu Outreach coordinator, nursery inspections, pest surveys Janet Lensing, PhD: janet.lensing@uky.edu State Survey Coordinator JD Loan: jdloan.1@juno.com Survey supervisor!12