Caterpillars and ornamentals

Published: Thursday, August 7, 2014 at 09:51 AM.

During late summer, caterpillars cause problems for gardeners all over our state.  As you know, caterpillars are the larval stage of butterflies and moths.  While many of the winged adults are attractive, the damage caused by the larvae certainly is not.  Because caterpillars are ravenous feeders, they can cause considerable damage in a short time.  Early detection and prompt counter measures are very important. 

There are many kinds of pest caterpillars for too many to cover in a single article.

Sod webworms and fall armyworms seriously damage lawns.  It’s not unusual for both to attack at the same time.  Webworms are the smaller of the tow species, reaching a length of only about three-quarters of an inch, compared to one-and-a half inches for army worms.  In general, both are greenish in the young sage turning brown as they mature.  Their feeding is similar, resulting in notched or ragged leaf edges.  However, webworms tend to feed in patches, while armyworms cause more scattered damage.

The orange dog caterpillar is a common pest on citrus trees.  It’s black with white markings, and slimy looking.  Its eggs, which look like small yellow beads, are laid on the newest plant growth.  At maturity, the orange dog becomes a swallowtail butterfly.

If you’ve ever suddenly felt a sharp, stinging sensation while pruning a plant, you may have come in contact with an Io (Eye-oh) moth caterpillar.  This caterpillar is pale green, with two stripes, one white and one maroon down both sides of its body.  It has many clumps of stiff poisonous hairs.  Touching these is painful to most people.  In some cases, the reaction is bad enough to require hospitalization.  The Io moth caterpillar, which is only one of several stringing varieties, if found on such plants as hibiscus, poinsettias, palms, and many others.

Caterpillars can be controlled mechanically, or with chemical sprays.  If the caterpillars are large, and few in number, they can be removed from plants by hand.  If egg masses are recognized, these can be destroyed before they hatch. Chemical control materials include sevin, Malathion, and Bacillus thuringiensis(Thur-in-gen-en-sis.)

Sevin is a stomach poison, that’s good to use on small caterpillars that are hard to find.  However, sevin isn’t a very good contact poison.  It can’t be used against caterpillars that are already quite large.

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