White Oak Defoliation
Common Oak Moth The Ohio Department of Natural Resources Division of Forestry has received fewer numerous reports of defoliation on white oak this spring (2005), than during the past 4 seasons.
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| Common Oak Moth caterpillar |
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| Phigalia |
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There are several caterpillars responsible for the damage. The predominant defoliators that have been identified include the common oak moth and a looper in the genus Phigalia. Both of these insects have only one generation each year.
The worst of the defoliation seems to be over and many of the caterpillars are already pupating. Most of the damage occurred in Scioto, Pike, Ross, Vinton, Lawrence, Jackson, and Gallia Counties. Two of the worst spots appear to be the area around Portsmouth and the area between Waverly and Chillicothe. These insects are causing damage to oaks in parts of West Virginia and Kentucky as well.
It is not unusual for inchworms, also called loopers, to show up in large numbers. These are native insects that periodically develop high populations, possibly triggered by stress, such as drought conditions. They are present in high numbers for a short time and then collapse due to predators and parasites. The Phigalia loopers are highly variable in color, but move with the typical tail-to-nose movement of an inch-worm. In addition to oaks, they also feed on a variety of hardwood hosts such as maple, wild cherry, elm and hickory.
The common oak moth, Phoberia atomaris, is also a native insect. It is nearly an inch long when mature, hairless, and generally dark brown and black in coloration. They have two rows of small, black triangles that occur down the length of the back of the caterpillar. The common oak moth was numerous and caused extensive damage in Ross County last year. This pest prefers to feed on white oak. Natural predators and parasites typically control this caterpillar after a couple of years.
Heavy defoliation in the early spring usually results in a second flush of leaves that uses the tree’s stored energy reserves. If trees were healthy prior to the damage, they will likely recover. Trees previously stressed by weather conditions or insect /disease problems will have a harder time maintaining their health. If drought conditions or other stress factors occur later this year, some tree decline and/or mortality will result. Two-lined chestnut borer and armillaria root disease are able to take advantage of the tree’s compromised condition and are often responsible for the decline and mortality in oaks.
If you have questions about a forest pest call your local forester.
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