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Garden Help Desk: Finding the best ways to squash bugs and eggs

By USU Extension - | May 20, 2023

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Always check the undersides of leaves when scouting for squash bug eggs and nymphs. Eggs are usually laid where two leaf veins meet.

We’ve had problems with squash bugs for several seasons and it seems to get a little worse each year. Spraying didn’t help much. Is there something better we can try?

Squash bugs are an annual problem for many gardeners. Insecticides can be effective for young squash bug nymphs, but they must be applied with good coverage throughout the plant canopy, on upper and lower leaf surfaces, and aren’t very effective for adult squash bugs. That may be why spraying wasn’t helpful for you. Another reason to try different control methods instead of spraying is that squash blossoms are pollinated by bees, and frequent use of insecticides can interfere with pollination.

It can be difficult to rid a garden of the bugs. Some gardeners even choose to skip growing squash for one season, hoping to break the cycle. It’s true that leaving squash out of your garden for a year can be effective, but there are other methods you can try if you can’t go an entire year without your favorite squash.

Healthy vegetable plants are usually less attractive insect pests, so be diligent about giving your garden good care — adequate fertilizer and deep, but not frequent, watering.

Squash bugs overwinter as adults under plant debris, in rock walls, firewood piles, litter and clutter, so a thorough cleanup in the garden every fall is very important. Remove or turn under all dead plants and weeds from the garden and around the garden at the end of the season. Don’t leave piles of old nursery pots, hoses and other irrigation supplies, clutter, etc. near the garden. Firewood should be stored as far away from the garden as possible.

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Tulle fabric like the row cover over these cabbage plants or ultra-lightweight bonded row cover material can be used to exclude many different insects. When excluding squash bug adults, though, it's important that the material is completely secured to the soil all the way around the edges so that there are no gaps or openings for squash bugs to crawl under.

Overwintering squash bugs usually show up in Utah County gardens in May, and egg laying peaks at about now (late May). That means it’s time to be scouting for eggs, nymphs and adults on your squash plants. Scout frequently. Look on the underside of leaves where leaf veins meet for clusters of eggs and crush them, cover them with petroleum jelly, pull them loose with duct tape or tear out that little section of the leaf and discard it. Grab and crush any adults or older nymphs that you find.

Adult squash bugs tend to seek shelter at night when they aren’t actively feeding. You can take advantage of this and make “traps” by laying a few old shingles, short pieces of cedar fencing, folded sections of newspaper, heavy cardboard, or similar materials on the ground near the base of the plants. Every morning, take a small bucket of soapy water into the garden, turn over the traps and grab any squash bugs that you see and drop them into the bucket. The soap in the water will let the bugs sink and drowned. Eggs are laid only by the adults that have overwintered, not by the new bugs that hatch, so every adult that you can eliminate early in the season can prevent hundreds of eggs later in the season.

If you are scouting for eggs and you happen to turn over a leaf with small, newly hatched squash bug nymphs, you can spray the nymphs with insecticidal soap or horticultural oil. Nymphs tend to stay on the leaf where they hatched for a day or two, so frequent scouting can help you to eliminate them before they spread out in the garden. If you find lots of nymphs on a leaf, it might be easier to just pull a large garbage bag over the leaf, tie the bag shut, cut away the leaf and discard it.

Scouting and trapping can keep the squash bug population low enough to prevent noticeable damage to your squash and many gardeners get good control with just those two strategies.

You can also try to prevent or delay egg laying by covering your planting completely (clear down to the soil with no gaps or openings) using ultra-lightweight insect-excluding row cover or tulle fabric as soon as you’ve planted your squash. You must leave the covering in place until after you see blossoms, then remove the row cover so that bees can pollinate the blossoms.

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Squash bug eggs are most commonly laid on the underside of leaves but can also be found on young stems.

If you find you’re tired of eating squash before the plants are tired of giving you squash, remove the plants to eliminate a late summer food source for any squash bugs that may still be around.


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