First you notice yellow or brown spots on the leaves of your squash and zucchini plants. Then the plant begins to wilt. Your established plants begin to lose runners. Younger plants die. It must be the arch nemesis of cucurbits: the squash bug.
When it comes to these garden pests, your best bet is to prevent squash bugs in the first place. Once established, they can be difficult to control as they have few natural predators. The tachinid fly and parasitic wasps will both prey on squash bugs, but thanks to a “noxious odor” the bug releases when attacked, even those have a limited impact on controlling squash bug populations.
Squash bug biology
From early to late spring (earlier in warmer climates and later in cooler regions), the squash bug emerges from its winter hideout and flies to cucurbit crops such as zucchini, summer squash, and pumpkins. Once there, they feed, mate, and lay eggs on the underside of leaves. The Extension program at Utah State University points out that a female squash bug may lay up to 250 eggs over several weeks. These eggs hatch about 10 days later.
In warmer regions, you may get two generations of squash bugs in a season, but in most areas, one generation is more common. As winter rolls around, adult squash bugs will shelter in plant debris, wood piles, compost piles, and field borders.
5 ways to prevent squash bugs from hiding out in your garden
The key to your efforts to prevent squash bugs is to keep them from overwintering. However, those efforts can begin as early as spring.
1. Row covers. Since we know that squash bugs emerge in spring and fly to feeding sites, one way to interrupt the cycle is to use floating row covers, so they don’t have anywhere to take up residence and feed or lay eggs. You’ll need to remove the row covers once the plants begin to flower, as you do want pollinators like bees and butterflies to reach them. By that time, however, your squash bugs may have moved on. (I like these row covers.)
2. Trap crops. Another way to prevent squash bugs from completing their generational cycle is to plant trap crops. The University of Massachusetts Center for Agriculture, Food, and the Environment reports that early plantings of Yellow Straightneck and Crookneck squash, as well as Blue Hubbard squash, are particularly effective trap crops. Once the squash bugs have laid their eggs, destroy the trap crop and interrupt the cycle of squash bug generations.
3. Skip the mulch. I admit it feels a little strange to write that, especially considering how much we promote mulch. However, given that we’re trying to prevent squash bugs from overwintering, taking away their habitat is one very effective way to do it.
4. Diatomaceous earth. It’s organic and effective against pests like slugs and snails, so why not squash bugs? I can’t vouch for this one, but Colorado State University Extension recommends diatomaceous earth around the base of your plants as a way to prevent squash bugs, so I imagine it’s worth a try. (I try to stick with Food Grade Diatomaceous Earth.)
5. Remove crops immediately after harvest. This goes back to the idea of removing the habitat as a way to prevent squash bugs. As soon as you harvest your crops, clean up the area, so the bugs don’t have a place to hide and overwinter.
There are other methods, as well. For example, crop rotation can work to remove the squash bugs’ food source, but that only works in large gardens where there’s plenty of room to spread out. For most of us with backyard gardens, crop rotation does have benefits, but not so much for preventing pests.
You can also use Neem oil sprays, but in order for it to work, you have to spray early on, before the squash bugs emerge from their eggs and in the nymph stage. Adult squash bugs are resistant to many pesticides.
Another option is to use a trellis and train your squash vines so they’re elevated. This won’t prevent squash bugs per se, but it will make it easier for you to spot eggs.
How have you dealt with squash bugs in your garden? I’d love to read your story in the comments.
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