Q. I'm worried about getting those caterpillars in my mulberry trees again this year. They even crawled under the garage door and into the house! I don't want to cut down my trees, but I don't know any other solution. What should I do?

A. The caterpillar commonly found in mulberry trees in late summer is probably the larval stage of a Tussock or Tiger Moth. It has a grey body with yellow tufts of "hair" and has a voracious appetite. The Mulberry caterpillar will feed on other ornamentals if their preferred food (mulberry leaves) is not available. In addition to completely defoliating a plant, contact with the hairs on the Mulberry caterpillar can produce a skin rash on some people, even after the caterpillar is dead.

Control is easiest when the caterpillars are young. Don't wait until they're crawling under the garage door! Apply any control measure, whether an insecticide or a biological control, soon after the first caterpillar is spotted, usually at the end of June or beginning of July. You will have to repeat applications as more caterpillars emerge.

There are several control options for Mulberry caterpillars. The first, simplest but hardest control option is not to try to control it at all. The caterpillars will not kill your tree. It is possible that after many, many years of being defoliated by the Mulberry caterpillar, the tree will be so stressed that it becomes vulnerable to some other agent, such as a disease. But for most homeowners, it is not the health of the tree that causes so much concern. It is the tree's appearance and the unsightly presence of hundreds of creeping, crawling caterpillars.

The second and least toxic control option is to spray the tree as soon as the caterpillars appear with a biological control agent called Bacillus thuringienis var. berliner, also known as Bt. Bt is not a contact poison like most insecticides, it must be eaten to be effective. It works by paralyzing the caterpillar's digestive system so that it stops feeding and dies - essentially from a nasty tummy ache. The smaller the caterpillar is, the less Bt it has to consume to be fatal. Since Bt is species-specific, it is not toxic to birds, pets, fish, bees, or humans. Bt will also work on many other troublesome caterpillars, such as cabbage loopers and tomato hornworms.

The third control option is the use of a commercial insecticide containing carbaryl (Sevin is one of several brand name insecticides containing carbaryl). A systemic insecticide containing acephate may also be effective in reducing populations. Never use a systemic insecticide on anything you're going to eat later. REMEMBER, these chemicals are broad-spectrum insecticides. They will kill all chewing and sucking insects, bees, and fish which come into contact with them. In addition, these chemicals are hazardous to humans and pets if swallowed or inhaled. Full protective gear should be worn when applying these chemicals, especially when applying them to a large surface area such as a tree canopy. Unfortunately, if you wait until the whole neighborhood is crawling with Mulberry caterpillars to introduce a control, the only recourse left to you, besides ignoring the problem, is a chemical insecticide. Just be certain to read and follow the directions on the label and protect yourself, your neighbors, and the environment from contamination.

NOTE: We have these larvae at our office and are going to rear them to the adult stage when it will be easier to identify. A more exact identification will be published in a later issue.