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Garden Column for the Salisbury Post Darrell Blackwelder September 2, 2004
Rowan County has succumbed to yet another invasion of caterpillars. In the early spring it was tent caterpillars on cherry and plum trees. Later in the summer millipedes invaded homes by the bucket. Fall webworms arrived last month flocking shade trees with ugly, spider-like webs. Now oak trees are being defoliated by huge numbers of orange stripped oak worms. These worms are literally stripping trees in a matter of days. The orange-striped oak worms are caterpillars that are about 1 1/2 to 2 inches long, black in color with several narrow, yellow-orange longitudinal lines. On the head is a pair of stiff, blunt spines, about the thickness of the body. The remaining segments of the body have pairs of smaller spines. The orange striped oak worm caterpillar generally appears in Rowan County in mid-August through September. The adult stage is a rather large moth. Moths emerge in June through August, mate and the females deposit their eggs on the underside of the host plants. Like all caterpillars, these have a ferocious appetite, defoliating large sections of various oak species, mostly willow and water oak trees. Often, these caterpillars can completely defoliate small trees in a matter of hours. A major concern of most homeowners is if the defoliation will kill their trees. Fortunately, defoliation occurs in late summer and the trees have amassed food supplies for next year’s growth. So, there really isn’t any serious damage to the trees other than aesthetics. There is only one generation per year and control measures are not necessary. If, however, control measures are necessary, such as to protect a small seedling oak, treat with Dipel, or Thuricide (both are Bacillus thuringiensis, a biological control), or use an insecticide such as orthene or Sevin. The other complaint is from the oak worm is the excrement or caterpillar poop littering sidewalks, driveways and anything else within radius of the tree. It’s a problem that can only be rectified with use of an insecticide. Spraying is not feasible in most situations and constant washing may be the only recourse. The one positive is there is less leaves to rake later this month.
Darrell Blackwelder is an agricultural agent in charge of horticulture with the North Carolina Cooperative Extension Service in Rowan County. For archived garden columns or other information, visit the Rowan County Master Gardener web site at www.rowanmastergardener.com , e-mail Darrell_Blackwelder@ncsu.edu
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