Description: Orange striped oakworms are most often recognized in the caterpillar stage because of their defoliation of oak trees. They have been referred to as a ‘stomach with legs’, because leaves disappear rapidly during the weeks they feed. The full grown caterpillars are 1 ½ to 2 inches long, black in color with orangeyellow stripes. The second segment of their body, right behind the head, has long black spines. The spines or ‘horns’ are used to scare predators away and do not have the capacity to sting.
The winter is passed in the pupa stage in the ground. Adult moths emerge from June to August and lay their eggs in clusters on the underside of leaves. The adult moth is 1 ¼ inches long with wings closed. They are reddish brown, translucent with a submarginal dark stripe and a white spot on each forewing. Over a one month period the female will deposit up to 500 eggs in a single cluster on the underside of an oak leaf, usually on the lower branches.
Symptoms: Young caterpillars feed by skeletonizing the leaf surface. Older caterpillars are defoliators and may consume all but the leaf midrib. They defoliate sections of various oak species and sometimes completely defoliate smaller trees. Because the oak worm ingests such tremendous amounts of feed, one of the ways it is discovered is the thickly scattered waste pellets that fall from tree foliage. On a quiet day, the pellets can be heard clattering down through the leaves and hitting the ground below.
Action: A healthy tree can re-foliate after some feeding. The caterpillar may need to be controlled if undesired amounts of waste are causing problems to decks, patios and pools. Smaller trees can be sprayed while larger trees need properly timed injections.
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