Inspector Findings in Kentucky

Purdue University website: http://hermes.ecn.purdue.edu:8001//http _dir/acad/agr/extn/agr/acspub/acsonline/%23E-11%23

The mimosa webworm attacks both mimosa and honeylocust trees. Widespread use of the thornless honeylocust as an ornamental has heightened interest in the control of this insect, because all clones (varieties) of the tree are susceptible to attack.

The damage is done by webworm larvae, which web the foliage together and skeletonize the leaflets, causing infested trees to turn brown as if scorched by fire. The insect has two generations each year. However, injury is most noticeable in August, when second generation larvae are at the peak of activity.

DESCRIPTION AND LIFE HISTORY

The adult mimosa webworm is a small, silvery-gray moth which has wings stippled with black dots. Moths of the first generation appear in early June, while those of the second generation are seen in late July and early August. Adults lay eggs on foliage and in the old webbing. The eggs are tiny, oval and at first pearly-white, but then turn pink as hatching time nears.

The full-grown larva is about l inch long and grayish-brown in color with five white stripes running length- wise down the body. It has a dark head, and the body is sometimes tinged with pink.

The mature larva pupates on the ground, on tree trunks, in old webbing left by feeding worms and in other sheltered places. In the case of the honeylocust, pupae are often hidden in a mass of thorns. The two generations often overlap, and all stages can be found during the summer. The second generation overwinters in the pupal stage.

SUSCEPTIBILITY OF HONEYLOCUST

Of all the thornless honeylocust clones, the Sunburst variety seems to be the most susceptible to webworm attack. This tree is often completely defoliated by the end of July. The varieties Shademaster, Skyline, Moraine and Imperial are less susceptible but still subject to severe injury.

The variety Sunburst should probably not be planted where the mimosa webworm is abundant. Also, mass plantings of any of the thornless varieties should be avoided unless the trees can be sprayed.

CONTROL RECOMMENDATIONS

Mimosa webworm can be controlled by a combination of sanitation practices and spraying. Since many of the webworm pupae overwinter in debris on the ground, leaves should be raked from under infested trees in the fall and corn- posted or burned. A number of insecticides are labeled for webworm control.

Ohio State website http://www.ag.ohio-state.edu/~ohioline/hyg-fact/3000/3054.html

Crown gall is characterized by growth of galls on roots or stems. While mostly found on woody plants, it affects some herbaceous plants as well. Although found on more than 600 plant species in over 90 families, the disease is of economic importance on relatively few ornamental plants. Some commonly affected ornamentals include rose, Prunus, (flowering cherry, flowering almond and ornamental plums), willow, and certain Euonymous species, especially wintercreeper.

Crown gall can reduce the productive life of plants. Deformation of tissues due to gall formation disrupts the movement of water and nutrients between roots and leaves. Stems are weakened and growth may be reduced with a general decline in vigor. The severity of the disease depends on the size, number, and location of the galls, and also on the susceptibility of the plant and age when infected. Galls at the crown of young plants have the greatest adverse effect and can cause stunting and failure to produce healthy leaves and blossoms. This disease may have little noticeable effect on older plants.

Galls may develop anywhere on stems and roots, but are usually found near the soil line. They vary from pea size up to several inches in diameter. Young galls are light colored and smooth.

Older galls become discolored, hard and woody, and eventually crack, decay and slough off. The texture at first is softer than the normal host stem or root tissue. The galls consist of disorganized host tissues. Secondary galls sometimes form above the sites of the primary gall on stems of some hosts. The secondary galls are usually smaller and occur as separate or unbroken elongated masses of tissue breaking through the bark surfaces. Unlike insect galls, crown galls are a solid mass of tissue all the way through.

Crown gall is caused by the soil-borne bacterium, Agrobacterium tumefaciens. The bacteria can persist in the soil for two or more years even in the absence of susceptible plants. Sometimes the bacteria are carried on seeds. Fresh wounds in stems or roots are essential for the bacteria to invade host tissues. These wounds commonly occur during planting, cultivation and pruning, and during propagation when grafting and taking cuttings. Soil insects and nematodes can also cause root wounds providing entry sites.

There are no effective chemical controls for this disease in the landscape. Cultural controls include:

1. Avoid unnecessary wounding (protect from injury).

2. Sanitation-remove infected plants.

3. Plant resistant plants in crown gall-infested areas.

4. Do not purchase plants with suspicious swelling near the soil line or on the roots.

By Lee Townsend and Ric Bessin, Extension Entomologists

Several large caterpillars can be seen in late summer. Often they are caught as the crawl across lawns in search of a pupation site. The common ones being sent in to us now are the cecropia caterpillar and the hickory horned devil. Both are spectacular, neither is harmful.

The cecropia moth caterpillar takes most of the summer to mature and is up to four inches long when fully developed. They are bluish green and there is a pair of yellow projections along the back on each body segment. The first three pairs are yellow balls with black spines. Cecropia caterpillars feed mainly on cherry, plum, apple, elderberry, box elder, maple, birch and willow, but will also feed on linden, elm, sassafras and lilac.

In early fall the mature caterpillar spins a spindle-shaped cocoon which is about three inches long. The cocoon is attached along its full length to a twig on the host tree. Inside the cocoon the caterpillar changes to a pupa, the life stage in which it spends the winter.

The hickory horned devil is the largest of the silk moth caterpillars, commonly reaching five inches in length. The long barbed horns on the forward end of the body make the caterpillar look intimidating but it is entirely harmless to humans. These rotund caterpillars feed on hickory, sumac, sweet gum, lilac, persimmon, ash and beech. They pupate in the soil.

Information on these and other impressive caterpillars is available in Entfact 008 Saturniid Moths. Color pictures of many can be seen on our web site at - www.uky.edu/Agriculture/Entomology/entfacts/misc/

This year 40 gypsy moths were caught in several Kentucky counties. Confirmed catches have been in Boone, Bracken, Campbell, Carroll, Fayette, Fleming, Franklin, Harrison, Jefferson, Jessamine, Kenton, Madison, Mason, Owen, Rowan, Russell, Trimble and Wolfe. Next year the areas in these counties where moths were caught will be massed trapped to determine if these catches were the result of accidental introductions or an infestation.

by Ric Bessin and Lee Townsend, Extension Entomologists

Numerous reports of large aggregations of ladybird beetles on homes and other buildings were first received in the fall of 1993. Usually we would not be concerned with lady beetles because they are beneficial insects, but these are congregating by the thousands on the sides buildings and if given the opportunity, moving inside. Fortunately, they are not poisonous, do not bite or sting, are not carriers of disease, and do not eat wood. But they can be a nuisance when they gather in very large numbers around windows and doors. This ladybird beetle, Harmonia axyridis, is new to Kentucky. Our first records only date back to a few specimens captured in Hickman county in 1992. This is an introduced species from eastern Asia. It is not known exactly how it became established in the United States. There have been numerous attempts (from 1916 until 1985) to establish this species as a biological control agent. This ladybird beetle is an important predator of scale and aphid pests on trees in Asia. The first specimens recovered in the US were collected in Louisiana during 1988. Since then the beetle has increased its distribution to include Mississippi, Georgia, Florida, South Carolina, North Carolina, Virginia, Oregon, Washington, and now Kentucky.

These oval, convex, 1/3 inch beetles are pale orange in color with 19 black spots on the wing covers. The 19 spots are arranged as a row of five spots just behind the pronotum, followed by two rows of six spots, and a forth row of two spots. The margins of the pronotum are white. They resemble Mexican bean beetles and squash beetles in general appearance, but have a different arrangement of spots. A fraction of these beetles are either without these spots or may only have traces of 4 to 6 spots on the wing covers. In Asia, this beetle occurs in at least 100 different color forms including black forms with orange spots.

The ladybird beetles are congregating on homes in wooded areas in search of overwintering sites. They usually select the west or southwest side of buildings for initial congregation sites. Some county agents have reported that after the beetles settle down on the side of buildings, many leave on their own by nightfall. It is likely these beetles will move into leaf litter, underneath boards or logs, or other protected areas after the first frost as preferred overwintering sites.

As usual, prevention is the key to keeping this ladybird beetle from getting into homes. Make certain that cracks along windows and doors are weatherstripped. Ventilation openings in attics should be screened or sealed as appropriate.

This lady beetle does not have a common name, although the multi-colored asian beetle has been suggested. However, we suggest the "halloween beetle" as a common name, considering the time of year it is most noticeable and its color.

By Bill Fountain, Extension Horticulturist

El Nino, La Nina, it seems like everyone blames these evil twins for everything. It isn't directly the fault of the weather that some of our crabapples and other spring flowering plants are not going to have large numbers of flowers NEXT spring. And no, we do not have the ability to predict late spring frosts and freezes before the preceding summer is over. But, what happens over the next two weeks will determine the potential for flowering for many of our spring flowering trees and shrubs. The key word here is: potential. This (mid-August) is the time of year when many plants form flower buds that will not open until next spring. Fully formed flower buds of apples, crabapples, cherries, plums, peaches, pears, quince, hawthorns, cotoneaster, and so many others will lay dormant inside buds, protected against winter's cold blast. Only after a predetermined number of hours of chilling (below 45 degrees F) to break down chemicals that prevent premature flowering is the flower finally able to open, and then, only after warm weather.

It is important to remember that the whole world runs on sugars made in plant leaves as a result of photosynthesis. Every living organism, including ourselves, is a guest on the planet earth of the plant kingdom. Our demise would be swift and catastrophic if all plants ceased photosynthesizing.

Now, step outside and take a look at the crabapples around your community. Many of them have been defoliated by scab and other pathogens or even insects like Japanese beetles. For what ever reason, if a plant does not have leaves it can't make sugars. It is short and simple - No production of sugars, no flower bud formation. In addition to the loss of foliage other factors that can prevent flower formation include stress caused by drought, low fertility and heavy shade.

Recommendations for improved flowering include:

(1) A good, deep watering (early to mid August) if soils are excessively dry.

(2) Fertilize in late fall (Thanksgiving to Christmas) to encourage good flowering a year and a few months later. Do not fertilize plants at this time of year. It is too late for improved fertility to encourage flowering this year. High levels of nitrogen may promote late season growth that will not be sufficiently hardy when winter comes.

(3) Control leaf pathogens and insects before excessive damage occurs.

Ohio State website:http://www.ag.ohio-state.edu/~ohioline/hyg-fact/3000/3053.html

Verticillium wilt, caused by the fungi Verticillium albo- atrum and V. dahliae, is a serious vascular disease of hundreds of woody and herbaceous plant hosts. Food crop hosts include everything from raspberries and strawberries, to tomatoes and potatoes.

Some of the many common woody ornamental host plants include ash, barberry, catalpa, elm, magnolia, maple, Russian olive, redbud, smoketree, tuliptree, and viburnum. One group of plants not susceptible to Verticillium wilt are all the gymnosperms, including conifers such as pine and spruce. While many landscape plants are affected, Verticillium wilt is not a major problem in natural forested areas.

Wilting of leaves and dieback of branches, often one at a time or on one side of the tree, are the most severe symptoms. This can occur over a number of years, with remission of symptoms in some years, or can rapidly progress to plant death in a year or two. Other symptoms of Verticillium wilt may include: marginal browning and scorch of leaves, abnormally large seed crops, small leaves, stunting, poor annual growth, and sparse foliage.

Sometimes large areas of cambial tissue die from infections by the fungus and opportunistic fungi such as Nectria develop in elongated cankers. Late season infections may not be noticeable until plants come out of dormancy with branch dieback evident.

All of the above symptoms can also be caused by other stress factors. A good field symptom that can set Verticillium wilt apart diagnostically is the discoloration of xylem and cambial tissue, visible as streaks if you cut into the wood. This discoloration is variable for different plants: generally greenish to blackish on maple, yellowish green on smoketree, and brown on ash.

This streaking is not totally diagnostic on two counts: 1) other fungi and other factors can cause discoloration; and 2) on some hosts and on youngest twigs, infection is not always accompanied by discoloration. However, vascular discoloration is a good field symptom that can then be followed up for confirmation by a diagnostic lab such as The University of Kentucky Plant Diagnostic Lab.

The Verticillium fungus can survive for many years in soil, making effective crop rotation difficult. The fungus infects plant roots through wounds and in some cases direct penetration of root tissue. Verticillium also is transmitted from plant to plant by grafting and budding.

From root infections, the fungus spreads upward in the plant through the vascular stream. The results of infection are tissue damage and plugging of xylem, robbing stems and leaves of needed water and minerals. The fungus is returned to the soil as plant parts fall or die, and tiny resistant fungal microsclerotia are spread by wind, in soil and on equipment. Many weed hosts are also susceptible; therefore the cycle of contaminated soil is hard to break.

Development of Verticillium wilt is favored by factors that stress roots, including wounding and droughty conditions.

1. Disease resistance. If Verticillium wilt is diagnosed at a particular landscape or nursery site it is prudent to replant into that area with a plant that exhibits resistance to this disease. A few common examples of plants typically free of this disease include: crabapple, mountain ash, beech, birch, boxwood, dogwood, sweet gum, hawthorn, holly, katsuratree, honeylocust, oak, pear, London planetree and sycamore, rhododendron, willow, and zelkova. The red maple cultivars Armstrong, Autumn Flame, Bowhall, October Glory, Red Sunset, Scarlet and Schlessinger have also been reported as resistant.

2. Keep plants as healthy as possible. Proper transplanting practices, proper water management to avoid droughts, a good fertility program, and pruning out dead branches are all good plant health care management practices. These can help limit infections and help limit the effects of these infections to some extent. Pruning out infected branches is useful as a general horticultural practice for overall plant vigor and aesthetics, but does not eliminate Verticillium from the plant since infections spread from the roots.

by John Hartman, Extension Plant Pathologist

In some circumstances, rust diseases can be very destructive to pines in Kentucky. Pine rust diseases are found more commonly in forest than in landscape environments. Like most rusts, pine rusts have alternate host plants, dicots such as oaks, currants, and asters. Often, these dicots are little damaged by the rust disease they host.

In general, pine rusts go through distinct growth stages on their different hosts. Beginning on the diseased dicot host plant, the fungus produces a telial stage with teliospores. From the teliospores, basidia and basidiospores develop and are conveyed by air currents to the nearby pine. Some weeks, months, or years after infecting the pine, the fungus produces spermagonia and specialized spores called spermatia which are important for sexual reproduction. Still in the pine, the fungus then develops an aecial stage with aeciospores. This stage is sometimes characterized by swelling of affected pine tissues. Aeciospores carried by air currents then infect the nearby alternate host plant. On the dicot, uredia and urediospores which can reinfect the dicot are produced before the rust fungus life cycle finally returns to the telial stage.

Pine Needle Rust, Coleosporium asterum, affects Austrian, Japanese black, jack, loblolly, longleaf, mugho, pitch, red, Scots, shortleaf, and Virginia pines. Needle rust is not as destructive as some of the other rusts. The life cycle of this fungus takes 1 year. Alternate hosts include aster, goldenrod, and other composites.

Eastern Gall Rust, Cronartium quercuum, affects Austrian, jack, loblolly, mugho, pitch, red, Scots, shortleaf, and Virginia pines. When a stem or branch is infected with the fungus, it typically produces a spherical swelling and kills the stem or branch and all distal branches within a few years. The life cycle of this fungus takes two years or longer. Alternate hosts include many oak species.

Western Gall Rust, Endocronartium harknessii, affects Austrian, jack, mugho, and Scots pines, with symptoms similar to those of eastern gall rust. There are no alternate hosts; the fungus lives its entire life on pine, becoming reinfected by aeciospores produced on pine.

Fusiform Rust, Cronartium quercuum f. sp. fusiforme, affects Austrian, loblolly, and longleaf pines. The disease is very destructive, causing swollen cankers on the affected stems and branches. In Kentucky, it is only found in some of the southern counties. The two-year or longer life cycle of this rust also has many oak species as alternate hosts.

White Pine Blister Rust, Cronartium ribicola, affects eastern white pine producing girdling cankers which are very destructive. Although the alternate hosts, currant, gooseberry, and other Ribes spp. grow in Kentucky, the disease is not very common here. Where it is common, regulations prohibit the growing of the alternate hosts near white pine.

Disease Management

1) Avoid growing pines near alternate hosts, or remove the alternate hosts, if possible.

2) Remove and destroy pine galls, or if necessary, trees with galls to break the disease cycle.