04-07-11

Question and Answer

Q. My question is, what can I do about a grub, worm or insect that bores into the root system of my pumpkin and zucchini plants, then eats the inside of the stem above the ground? This seems to occur about the time the fruit has set on, or at least that is when the vine begins to die.

I have dug holes and lined them with landscape cloth, leaving the cloth to stick out of the ground about 4 inches and filled the hole with top soil, which I purchased at the garden center, thinking maybe they came in from the soil.

To make a long story short, it didn't work. Any help you could supply to rid my soil from these pests would be greatly appreciated.

A. You have just perfectly described the squash vine borer, a common pest of pumpkin and both summer and winter squash. The insect is a clearwing moth that lays eggs at the base of the plant stems in June and July. The larvae that hatch from the eggs then burrow into the stem and feed on the interior, pushing large amounts of greenish-brown frass out. By the time you see the sudden wilting of the stems, it is too late -- the damage is already done. Any sprays applied then will not kill the larvae inside the stem.

Use of floating row covers early in the season before the plants bloom can help prevent egg-laying by the adults. You'll need to remove the covers during bloom to allow pollination. Since this pest overwinters in the soil, removal of plant debris and fall soil cultivation can provide some control, but no need to line your planting holes with landscape cloth. If you had problems last year with this pest, be ready to provide early intervention this year. In addition to row covers, Purdue Entomology publication E-21, "Controlling Insects in the Home Vegetable Garden," lists four insecticides labeled for control of this pest: bifenthrin, carbaryl, esfenvalerate and permethrin. You can find this publication online at http://extension.entm.purdue.edu/publications/E-21.pdf. You can see photos and additional information on this pest at http://www.ppdl.purdue.edu/PPDL/hot08/7-14.html.

Note from Rosie:
In response to an earlier column, a reader wrote in to recommend a brand of copper fungicide to control tomato disease. I am glad that you had success in your garden and appreciate your wanting to share that information with our readers. Actually, there are a number of brands of copper fungicide for sale in Indiana that are registered by the EPA and labeled for use on tomatoes. However, according to Purdue plant pathologists, when compared to the active ingredient that I mentioned in the column, copper fungicide is of limited effectiveness in controlling this disease. In addition to providing research-based information, as a Purdue Extension Specialist I aim to neither endorse nor discriminate against specific brands or companies. So I hope you’ll understand why I declined to publish your recommendation in this column. I greatly appreciate your interest and the opportunity to explain why some options might not be included. And, of course, sometimes it might be that I just overlooked or didn't know about a particular option. I really do welcome your letters!