Q: I read your answer to a reader regarding his dying zucchini plant, and I wanted to ask what we as gardeners can do to eliminate this pest. For the past two years, I planted pumpkins and have been frustrated with this bug. I read one article that said to make sure the garden is clean: I burned, raked and organized the garden. Then I planted barley in the fall, turned it under in the spring and sprayed with Sevin and Rotenone. I had beautiful pumpkin vines and fruit; however, after returning from a weekend at the beach, I found sick and dying vines and the fruit under heavy assault from bugs.

A: The squash vine borer has four life cycle stages: the egg, larva, pupa and adult. Even though you tried to kill the first three stages before you planted the pumpkins, the adult moth flew over to lay new eggs on the newly planted vines.

The pupa stage spends the winter in the garden soil. It is hard to see, even if the soil is tilled up, and is pretty much impervious to insecticides. Rotating crops and tilling the soil are good ideas, but in this case they are not effective at preventing the borer. After developing into an adult that looks similar to a small wasp, the female moth lays eggs on the main stem of the vines and on the leaves. Once the eggs hatch, the caterpillars on the main stem create a hole in order to bore into the hollow stem. When the caterpillars on the leaf walk down to the main vine, they too make their way to the hollow stem.

The main effort should concentrate on preventing the eggs from hatching and keeping the caterpillars from getting into the vine. Once they are in the vine, they can eat for about a month without causing noticeable damage; they are virtually impossible to reach with insecticides at that time.

In northern states, only one generation develops per year. After killing the vine, the caterpillar ventures into the soil and pupates until the following spring. The one adult generation usually disappears around the Fourth of July. Waiting until after this time to plant susceptible vine crops will be OK, unless you are far north and plant a slow to mature crop.

Once planted, a pumpkin that matures in 90 days will be ready by mid-October; however, one that grows in 120 days will miss Halloween — it might make a good pie at Thanksgiving, if it can survive any frosts.

Plants put into the garden earlier than July can be easily protected with row covers. These wide cloth strips allow sunlight, air and water to pass, but keep insects out with its tight mesh. The vines will grow well under the cloth, but bees won't be able to reach the flowers to pollinate. You can plant a self-pollinating variety, hand-pollinate the flowers, or keep the covers off for the rest of the summer to let the bees work. Don't plant the vines in the same place as a previous year, since the borers could hatch into adults under the row cover.

In southern states, with more than one generation of borers each summer, the row cover can be left on during most of the season.

An unusual method used to create a row cover involves concealing a small vine with pantyhose — let the vine grow down the legs in its own row cover until the beginning of July. Then remove the toe to release the vine, or cut the entire pantyhose.

Without row covers, you can spray the vines twice a week with insecticidal soap. Or try a product containing the bacteria Bacillus thuringiensis, which only affects caterpillars of moths. These sprays will kill the tiny eggs and caterpillars before they find the vine. Some products include a syringe to inject the vine's hollow stem with the bacteria or beneficial nematodes; the caterpillars will die in the vine.

As the vines develop from the main plant, sometimes they can be covered with soil in order to produce new roots in several locations. If a borer damages a section of the vine near the original plant and roots, the remaining sections can remain alive with their own roots.

If you miss a borer, you can inspect for the hole as well as the droppings, which it pushes out; they are known as frass. Slit the vine with a knife where you see the frass, and you should find the caterpillar. This procedure also damages the vine, but it can prevent the entire vine from being killed — especially if there are new roots in other places.

E-mail questions to Jeff Rugg, Kendall County unit educator, University of Illinois Extension at jrugg@uiuc.edu. To find out more about Jeff Rugg and read features by other Creators Syndicate writers and cartoonists, visit the Creators Syndicate website at www.creators.com.

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