by Shane Harris, Regional Extension Agent
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Published  in The Outlook and The Dadeville Record

Feeding Caterpillars Can Be a Nuisance

Pest of the week: Caterpillars.  Although I briefly mentioned feeding caterpillars last week, an abundance of calls lately convinced me to dedicate an entire column to some of the most popular caterpillars you might see.  A lot of caterpillars have been found lately feeding on trees and other plants around homes.  This is really just a minor problem since it is very unlikely that they will kill the plants they are eating on.  But the results of their feeding - the unsightly defoliation of the plant and the shower of fecal droppings - could be categorized as pure nuisance. 

Azalea Caterpillars

If you find caterpillars on azaleas, more than likely the culprits are azalea caterpillars, These caterpillars are about ¼ to ½ inch long and red to brown with white or yellow stripes. Full grown, they are two inches long with a red head and legs with broken white stripes. They almost always feed in groups. Oddly enough, they rear their heads and tail ends up when disturbed.

Azalea caterpillars can really eat up the leaves of an azalea if nothing is done to stop them. Use the insecticide Sevin to chemically control them but this method is only effective on the small caterpillars. Remove the larger caterpillars by hand and put them in a sealable bag or in a container of soapy water. Don't worry about picking them off, azalea caterpillars do not bite or sting.  

Yellow-Striped Oakworm

A newer caterpillar pest that has been found lately on oak trees is the yellow-striped oakworm. They are black with yellow stripes and have two prominent black horns that arise from just behind the head. These caterpillars can potentially defoliate the entire tree as seen on a few small landscape oak trees.  Although they have been found on willow oaks, overcup oaks, and southern red oaks, they may not have a preference regarding what type of oak trees they feed on. 

For most homeowners, the concern lies with the defoliation, large numbers of caterpillars, and the falling frass (droppings). On the smaller planted landscape oak trees, any major defoliation will probably be detected.  On the much larger oak trees, the presence of caterpillars and damage may not be noticed. If deemed feasible to take action and control them, Sevin is the recommended insecticide.  Otherwise, don’t worry too much about it; they shouldn’t kill the tree.

Fall Webworms

One of the most noticeable species of caterpillar is the fall webworm.  They attack many deciduous trees and shrubs, but are most commonly found in pecan, black cherry, persimmon, and sourwood trees.  Their webs enclose the foliage on ends of branches and are seen in summer and fall. Treat with acephate, Sevin, or Dipel when the webs are first noticed and saturate thoroughly. As an alternative to spraying, webs and larvae can be removed and destroyed by hand late in the day.

Fall webworm is not usually a serious pest in natural forest stands. Infestations are of greatest concern on shade, ornamental, and urban forest trees. Here, loss of foliage and unsightly webs seriously reduce the aesthetic and environmental values of the trees. The natural enemies of fall webworms, such as birds, assassin bugs, parasitic wasps, and disease typically keep their population and potential damage at low levels and under control.
           
Cabbage Worms & Loopers

As the fall garden gets cranked up, you may notice something has eaten holes in the leaves of your collards, cabbage, broccoli, cauliflower, and lettuce. The perpetrators are most often going to be cabbage worms or cabbage loopers. These vegetable garden caterpillars attack the leaves, chew holes in them for their meal, and most often ruin the edible portion of these plants.

Actually finding a cabbage worm or cabbage looper on the vegetable plants is quite difficulty as they tend to blend in with the leaves. The cabbage worm, the larva of a white butterfly often seen hovering around green crops, is light green and can get up to about 1½ inches long.  The cabbage looper is about the same color and size of the cabbage worm except it bends its back like that of an inchworm when it crawls.


There are a few things you can do to help control cabbage worms and cabbage loopers. Cover your plants with cheesecloth or floating row cover to prevent egg-laying. Handpick the green worms as soon as they are found or damage is noticed. Spray plants with Bacillus thuringiensis (Bt), sold a Dipel and Thurcide, when worms are still small. Remove alternate host weeds, such as wild mustard and shepherd's purse, from the garden. Interplant a hot pepper plant between every two cabbage plants to help deter them.


For more information, contact the Tallapoosa County Extension office at 256-825-1050.