Inspector Findings in Kentucky

Nursery License Renewal

You should have received your nursery license renewal form within the last week.  We apologize for not getting those out to you sooner.  Hopefully you will the new application process simple and easy to use.  Let us know what you think.

Calico Scale Update

Dr. Dan Potter has observed that the calico scale is in the settled crawler stage on leaves.  This means that egg hatch is complete and the young crawlers from these eggs have found a place on a leaf and have begun to feed.  While feeding, they are beginning to produce their waxy covering which will protect them.  Oils and insecticidal soaps will provide control during this stage.  They should also be susceptible to insecticides although control may not be quite as good.

Stem Blights Can Kill Vinca Ground Covers

by John Hartman, Extension Plant Pathologist

Landscape beds containing vinca, a leafy ground cover, are showing symptoms and signs of stem blights and shoot dieback.  Recent warm humid weather has promoted the two main diseases that cause stem blights of vinca.

Stem blight, caused by the fungus Phoma exigua var. exigua is a serious disease of Vinca minor (periwinkle) in Kentucky.  Stem blight causes wilting and dieback of shoots.  Black lesions girdle the base of affected shoots and tiny black pycnidia, fruiting bodies of the fungus, are found in the lesions.  The fungus overwinters on old infected runners, often hidden from view by the new growth.  Shoot dieback symptoms may progress to death of entire clumps or patches of vinca, resulting in an uneven ground cover.  Stem blight can be mistaken for root rot caused by Rhizoctonia, which can also develop black stem lesions.  However, stem lesions from root rot infections do not contain the tiny black pycnidia. 

Infected plants should be removed from the bed.  Thinning of vinca beds and reduction of overhead shade will help reduce stem blight.  Chipco 26019, Cleary's 3336, Domain, or Zyban can be used if fungicides are needed for control.

Spider Mites

From American Rose Society web site Author:  Jolene Adams

Two-spotted spider mites can be rusty green, greenish amber or yellow and they have eight legs. Overwintering females are red or orange. These mites have two (sometimes four) black spots on top. They are very small, but still visible. The best way to see them is with a small magnifying glass.  The eggs vary from transparent and colorless to opaque straw yellow.

If spider mites infest your roses, you will begin to notice a dull appearance to the leaves. The undersides will feel "sandy" or rough. Fine webbing will appear on the undersides of leaves and in leaf axils. Leaves will begin to lose their color and become dry and lifeless. The leaves soon die and dry up.

Biology

Two-spotted spider mites are widely distributed in the United States and feed on over 180 host plants, including roses. Once a plant is infested, the mites spread onto nearby crops and ornamentals. Two-spotted spider mites pierce the epidermis of the host plant leaf with their sharp, slender mouthparts. When they extract the sap, the tissue of the leaf collapses in the area of the puncture. Soon a spot without green color forms at each feeding site. After a heavy attack, an entire plant may become yellowed, bronzed or killed completely. The mites may spin so much webbing over the plant that it becomes entirely covered.

Though insects and mites are in a group called the Arthropoda (meaning jointed foot), because jointed legs are common to both, spider mites are not actually insects. Being more closely related to spiders, they derive their name from the thin web that some species spin.

Two-spotted spider mites overwinter as adults in the soil or on hosts such as violets and hollyhocks. In mild winter weather, two-spotted spider mites continue to feed and lay eggs, although development in the winter is much slower than in the summer. In warm weather, six-legged larvae      hatch from the eggs. They develop into eight-legged nymphs, which pass through two nymphal stages. After each larval and nymphal stage, there is a resting stage. The adults mate soon after emerging from the last resting stage, and in warm weather the females soon lay eggs. Each female may lay over 100 eggs in her life and up to 19 eggs per day. Development is most rapid during hot, dry weather. A single generation may require as many as        20 or as few as 5 days to reach adulthood and begin producing offspring.

Control

Control of spider mites depends heavily upon an understanding of the biology of the mites. The mites are usually found on the underside of leaves.  Thorough application of a miticide to the underside of the plant foliage is essential for good control. An alternative to chemical controls is a strong water spray applied to the undersides of the leaves every three days during hot weather. Miticide applications may be needed 7 to 10 days apart to kill mites that were in the egg and resting stages during the first application. In hot weather, an eye should be kept on the plants to check for reinfestation or for the offspring of mites missed on the first application.

If you choose to use a miticide, read the label carefully and apply as directed. Mites easily become resistant, so NEVER dilute the miticide – this will only ensure that future generations of mites can resist the miticides you use.

Scab Has Nearly Defoliated Susceptible Crabapples

by John Hartman, Extension Plant Pathologist

Scab symptoms.  This common fungal disease is a serious problem in Kentucky on many flowering crabapple varieties, causing spotting of the leaves, premature defoliation, and unsightly corky spots on the fruit. Spots on the new leaves appear olive-colored and velvety. Later, the infections appear as olive-green or brown circular spots, with raised or puckered leaf tissue underneath. Scab spots may appear on leaves anywhere on the tree.  Typical fruit lesions are distinct, almost circular, rough-surfaced, olive-green spots, which later turn brown to black. When severe infections take place, the leaves yellow and the tree may lose almost all its leaves by midsummer. This year, because of lengthy leaf wetness periods this spring, defoliation is occurring even earlier than usual.

Scab life cycle.  The apple scab fungus, Venturia inaequalis, overwinters in old, infected, fallen leaves.   In spring, the fungus produces spores which land on crabapple foliage or fruit and infect the plant if the tissue surface is wet for several hours.  The fungal infection results in leaf lesions, where more spores are produced to begin additional cycles of infection throughout the growing season.  Secondary infection may also occur from spores produced on scab lesions found on the twig growth of extremely susceptible crabapples such as Malus 'Almey,' M. 'Hopa,' and M. x purpurea 'Eleyi.'

Control.  Use scab-resistant varieties in new plantings.  Cultivars such as 'Harvest Gold,' 'Louisa,' 'Mary Potter,' and 'Prairiefire' are good choices.  Scab infection on established trees may be prevented by three to five applications of fungicides at 10 to 14 day intervals starting as soon as bud growth appears and continuing until mid June.  Scab is most severe during wet growing seasons, so fungicide applications can be adjusted to weather conditions.

Potato leafhopper

From the University of Illinois website, Author: Raymond A. Cloyd

Potato leafhoppers attack many landscape trees, such as maple, crab apple, birch, and ash. Red maples are most susceptible; silver, sugar, and Norway maples are more tolerant. Potato leafhoppers possess piercing–sucking mouthparts that they use to feed in the vascular                    tissues of plants. As they feed, they inject a toxic fluid into plant tissue. Feeding, especially on maples, causes stunted tree shoots and leaves that curl downward with brown edges. On other plants, such as ash, potato leafhopper feeding creates small white or yellow spots on leaves, resulting in a stippled appearance because potato leafhoppers remove the chlorophyll (green pigment) from the leaves.  Potato leafhoppers don’t overwinter because their eggs are very sensitive to cold temperatures. They winter in the Gulf of Mexico and are blown north into Illinois by prevailing winds from around early May to early June.

Potato leafhopper adults settle into alfalfa fields during the early spring migration; they may then migrate onto ornamental plants during the first cutting of alfalfa. Adults are small (approximately 1/16 inch long), wedge shaped, and pale green with white eyes. Females lay eggs into the veins on the underside of leaves. Eggs hatch in six to nine days into light green nymphs that are found on leaf undersides and tend to move sideways when disturbed. Nymphs may undergo five instars before molting into adults. Adults and nymphs are similar, except that adults are larger, have wings, and can fly. The wings are held rooflike over the body. Empty white cast skins on the underside of leaves provide evidence of potato leafhopper activity. There are three to five generations per year.

Insecticides must be applied before potato leafhoppers cause plant damage. Control can be obtained with the use of pyrethroid insecticides such as bifenthrin (Talstar), cyfluthrin (Tempo), lambda-cyhalothrin (Scimitar), and permethrin (Astro). If damage has already occurred, insecticide applications will prevent further damage, and new growth will appear normal above the damaged leaves.  Regular scouting helps minimize the potential for potato leafhoppers to cause severe foliar damage.

Dogwood Diseases Are Appearing

by John Hartman, Extension Plant Pathologist

Dogwood anthracnose.   The fungus Discula destructiva, cause of dogwood anthracnose has been active in some eastern Kentucky dogwood plantings this spring.  Specimens with dead shoot tips, dead leaves hanging from infected twigs, dead twigs, and dead leaf blotches have been observed in the Plant Disease Diagnostic Laboratory this week and also on recent field trips.  Dogwood anthracnose is most likely to occur in moist, heavily shaded landscapes.

Powdery mildew.  Powdery mildew symptoms and signs are beginning to appear on landscape dogwoods in central Kentucky.  The powdery mildew fungus (Microsphaera spp. and/or Phyllactinia spp.) is active all summer and the foliage of infected dogwood trees will gradually deteriorate.  Humid weather favors powdery mildew.  Because humidity levels were low much of last summer due to the drought, less dogwood powdery mildew was observed last year.  If valuable specimens are to be protected with fungicides, applications must begin now.  Use Immunox, Banner Maxx, Eagle, Cleary's 3336, Heritage, Cygnus, or Compass for best results.

Gypsy Moth Trapping

If you happen to drive around certain parts of Kentucky you may notice triangular traps tacked to trees along roadsides.  These traps are used to attract male gypsy moths with a sex pheromone.  The gypsy moth is an extremely important pest and one that we are trying to keep out of the state as long as possible.  This year, along with our normal trapping regime, we are cooperating with the US Forest Service in their Slow the Spread (STS) campaign.  This program calls for trapping ahead of the leading edge of gypsy moth infestation at a high rate.  The counties where this is being done include Boyd, Greenup, Lewis, Mason, Bracken, and Robertson.  This year, over 7,000 traps have been placed in those counties along with the following counties: Rowan, Fleming, Bath, Elliott, Knott, Magoffin, Perry, Floyd, Henry, Gallatin, Carroll, Trimble, Oldham, Owen, Breathitt, Owsley, Lee, Wolfe, Kenton, Campbell, Boone, Carter, Trigg, Livingston, Lyon, Marshall, Calloway, Leslie, Harlan, Bell, Fayette, Madison, Garrard, Wayne, Whitley, McCreary, Lawrence, Johnson, Martin, Morgan, Laurel, Clay, Knox, Grant, Pendleton, Harrison, Boyd, Greenup, Bracken, Lewis, Robertson, Mason, Estill, Powell, Montgomery, Jackson, Nicholas, Menifee, Rockcastle, Letcher, Bourbon and Shelby.

The trappers will check the traps once during the month of July to determine if there are any positive catches.  Beginning the first of August, the trappers will begin removing the traps.  Any area that caught a gypsy moth this year will be massed trapped next year in order to determine if the area has a population of moths or if it was an accidental introduction.

Landscape Plant Diseases Observed At Plant Diagnostic Workshop

by Jen Flowers, Julie Beale and John Hartman, Dept. of Plant Pathology

The tri-state plant diagnostic workshop held in Boone County on June 9 was well attended and many different diseases of landscape plants were observed.   The following list was prepared to inform County Extension Agents and landscape professionals of the current landscape plant disease situation.

Austrian pine - Sphaeropsis tip blight and pine wilt disease caused by the pine wood nematode. 

Flowering crabapple - powdery mildew, scab, and cedar-apple rust.

Holly - black root rot.

Hosta - foliar nematode, bacterial soft rot, southern blight, sun scorch, and black vine weevil.

Maple - anthracnose and root/soil problems causing leaf scorch and excess live seed formation.

Oak - leaf blister and many kinds of insect-caused galls.

Redbud - Verticillium wilt.

Various hosts - crown gall, herbicide injury and eriophyid mite galls.

Barberry Bush Fights Bacteria

By Alternative Medicine Update web site

The barberry bush (Berberis vulgaris), which produces a natural antibiotic called berberine, can combine with antibiotics to make the antibiotics more powerful, according to recent findings published in the Proceedings of the National Academy of Sciences.

So-called super germs – those that resist even the most powerful antibiotics – have evolved as a result of antibiotic misuse and overuse, and are becoming a common problem. In the lab, researchers found that berberine combined with antibiotics to inhibit the growth of staph, one of the most drug-resistant germs.

Holly Leafminers

Univ. of TN Ag Extension Publication SP290-T

Holly leafminers are the most injurious pests of holly in the eastern United States. The holly leafminer was introduced from Europe. This insect is a primary pest of American or Christmas holly. Injury results from the larval mining activity just under the upper leaf surface. Additional damage is caused when females repeatedly puncture the leaves with their ovipositor (egg-laying structure). Punctured leaves become deformed.

Description and Life Cycle

The European species of leafminer, Phytomyza ilicis Curtis, overwinters as a larva in the mines. Larvae are about 1/8 inch long and yellow to white. Pupation occurs in March and April. Small, black, adult flies, 1/8 inch long, begin to emerge in May or about the time holly twigs have three to four new leaves. Adults feed for about 10 days before laying eggs. During this period, females make feeding punctures on the undersides of new leaves. Both males and females then feed on the sap exuding from these punctures. These punctures resemble pinpricks and may be quite numerous (up to 50 on a single leaf). Such injury results in distortion of the leaves. Eggs are laid in the punctures.

After hatching, larvae mine under the upper leaf surface. Mines are threadlike and inconspicuous at first, but by late autumn they widen into blotches or blisters. Another species, the native holly leafminer, Phytomyzail icicola Loew, produces very slender mines packed with frass (excrement) and may be found on the same tree with P. ilicis. Larvae remain in the mines for nine to 10 months before pupating in the spring.

Control

Apply trichlorfon, chlorpyrifos or diazinon for adult fly control in early May when the black flies are seen around new growth. Use acephate, imidacloprid, oxydemeton-methyl or dimethoate for control of mining larvae.  Dimethoate can be used on English and American holly, but should not be used on the Burford holly variety.