Controlling Squash Bug and Squash Vine Borer

Every gardener wants to grow a successful crop of zucchini and both yellow straight neck and yellow crooked neck squash. Why not? These are very delicious veggies and each produce a bounty of squash when insects are not an obstacle. Yet, these aforementioned squash plants, along with many others, are an easy target for both squash bugs (SB) and squash vine borers (SVB). These two insects can disrupt plant productivity and will typically kill squash plants if not controlled. This post will discuss a few preventative measures that can help with avoiding much of the plant damage caused by SVB and SB.

The first matter to discuss is the distinction between SB and SVB. These guys are not the same insect. The SB lays groups of reddish-brown colored eggs on the undersides of leaves while the SVB typically lays only a few brown colored eggs near the base of the plants main stem. When a SB egg hatches it unleashes a tiny nymph which promptly begins feeding on external plant tissue. Unfortunately, and because their are 15 to 30 eggs in each lay this means you’ll have 15 to 30 nymphs feeding on your plant. In contrast, and upon hatching of the 1 or 2 SVB eggs, a larva emerges from each egg and burrow into the interior of a main stem. If left unchecked, both insects can cause serious damage and can render the squash plant unproductive in a very short amount of time.

During the 2022 season, I evaluated the use of a physical control method to block the adult SVB moth from laying her egg on the plant’s main stem. This involved making a collar out of aluminum foil then placing it around the main stem. It should begin at about 1/4” below where the top soil and main stem meet. Continue covering the main stem until plant growth permits you from doing so. Revisit plants frequently to repeat the procedure. By the way, there are several U-tube sessions on this method should you require more insight.

At St. Joseph Street Community Garden, the results were somewhat effective however the moth stage of SVB is pretty sneaky and was capable of laying an egg or two close to the aluminum on about 30% of the plants.

Should you witness an eventual attack by SVB larvae you still have an opportunity to stop them in their tracks. To do so, some gardeners advocate spaying Bacillus thuringensis (Bt) inside the area where the larvae is located or cutting the stem longitudinally to extract the larva that’s doing the damage. I know, this seems like a lot of work! Honestly, I simply did not have time to do either.

As for SB, I spent time at checking plants for egg masses and simply removed their eggs by hand with the assistance of double-sided tape. Quite frankly, the eggs don’t stand a chance. In addition to manual removal I sprayed neem oil and a insecticidal soap, about once a week, to discourage egg laying. However, It’s highly likely that you’ll have missed a few egg masses so once you see leaf wilting and leaf discoloration (yellowing), immediately remove affected leaves and take them out of the garden. Overall, control of SB worked pretty well and I believe that we obtained good control. These control measures will be repeated in 2023.

Honestly, and after talking with a lot of good gardeners, some have stopped trying to grow squash. But because I believe in growing squash, I will continue working on SB and SVB control methods. The additional strategy will rely on planting a greater number of squash plants and employ succession planting in order to have squash during the entire growing season. There are a few other things I’ll try but I’ve decided to not talk about these tactics until the end of the 2023 season.

Most important, if you have good organic control strategies against SB and SVB, please share same with The Garden Dreamer.

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