Zukes Croak... Squash Vine Borer

Help! My zucchini are dead!

Many people will tell you that zucchini are a fool proof crop but not so for me. Each year, squash vine borers kill my zukes in early August. This insect bores through the stems and wrecks the plants plumbing, resulting in wilted and then dead plants. Squash vine borer problems are easy to diagnose. The stems, at ground level, are an unsightly mess of chewed plant bits. Yellow frass (caterpillar crap) often oozes from wounds. Dig around in the stems and you’ll find a nice fat larvae, eating the stems from the inside out. Plants wilt because the water conducting tissue of the plant is destroyed.
Plants will limp along, partially damaged for a long time, but they eventually wilt and die. No more zukes. By this time maybe you’ve had enough squash or your perhaps neighbor’s crop is just coming on.
What can be done?. I haven’t tried the frequently describe method of slitting open the zuke stems and stabbing the squash vine borer larvae with a wire. Done early enough this might work. A sure-fire method is to apply an insecticide at the base of the plant stems where female squash vine borers lay their eggs. Most over the counter vegetable insecticides will do the job. Apply in late June and early July and you should kill the larvae that hatch from recently laid eggs. Note that the entire plant does not need to be treated, just the stem, where it enters the soil.
It’s too late for insecticide treatments this year. So, make a note in your garden journal and prepare for 2009. Check out Penn State’s football rival, Ohio State, for a very thorough description of this pest and all of the control options.