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Squash Vine Borers Strike Again: This Time They’re in the Produce!

Green produce with yellow-orange dust on it.
Figure 1. Sawdust like debris on zucchini skin. Courtesy: Adam Varenhorst.

In a previous article, we covered monitoring our gardens for squash vine borer moths. The larvae of the squash vine borer can wreak havoc on zucchini, pumpkins and other squash plants by boring into the stems and slowly killing the plants. Unfortunately, they’ll do even more than just kill the plant. That’s right, they will also invade the developing produce.

While scouting my garden this week I noticed an odd marking on one of my set zucchinis (Figure 1). As I investigated closer I noticed that it wasn’t a mark, it was a sawdust-like powder. I quickly picked the zucchini and cut around the sawdust and I was shocked to see that there was a squash vine borer larva present in my zucchini (Figure 2).

Sideview of cut zucchini showing a small white caterpillar with a black head.
Figure 2. Squash vine borer larva feeding on flesh of a zucchini. Courtesy: Adam Varenhorst.

Squash vine borer larva are white in color with a black or dark brown head capsule. As they mature, they develop a dark segment directly behind the head. Since these larvae are in the produce the best course of action is to extract them by cutting around the entry hole.

To prevent spoilage on the vine, monitor your zucchini for any signs of feeding including the small circular piles of sawdust. We don’t recommend applying insecticides as the insect is inside of the plant and the insecticides won’t be effective and will only delay harvest.

White caterpillar with dark head feeding on the flesh of a pumpkin.
Figure 3. Squash vine borer larva feeding on flesh of a pumpkin. Courtesy: Jim Jasinski, Ohio State University Extension, Bugwood.org.

In addition to zucchini, squash vine borer larvae are known to infest other produce including pumpkins (Figure 3). Routinely monitor your garden and, when possible, harvest produce early to prevent infestation.