homepage logo

Garden Help Desk: Frequent inspection of plants can help control squash bugs

By USU Extension - Special to the Daily Herald | May 11, 2024
1 / 5
If you seem to have squash bugs every year, scout for squash bug eggs at least a few times a week. Egg clusters are usually found where two leaf veins meet.
2 / 5
An adult squash bug.
3 / 5
Squash bug eggs are most often laid on the underside of the squash leaves, but they can occasionally be found on other plant parts, like this leaf petiole on a crookneck squash plant.
4 / 5
Squash bug nymphs often stay together for a short time where they've hatched . It can be more efficient to simply remove the leaf instead of trying to remove the bugs. Pulling a large garbage bag over the leaf first will prevent any small nymphs from escaping.
5 / 5
These young squash bugs are in a spot where they can't be crushed or removed without damaging the plant. A quick spray of insecticidal soap or horticultural oil is the best way to deal with this.

We’ve already had several questions this spring about yearly problems with squash bugs in home gardens. Today, let’s do a basic review of squash bug management so you can be prepared before they show up in your garden.

Squash bugs are an annual problem for many gardeners, and it can be difficult to rid a garden of the bugs. Some gardeners even choose to skip growing squash for one season with the hope of breaking the cycle. It’s true that leaving squash out of your garden for a year can be effective — if your neighbors aren’t still growing squash — but there are other methods you can try if you can’t go an entire year without your favorite squash.

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. Squash blossoms are pollinated by bees, and frequent use of insecticides can interfere with pollination, so using different control methods instead of spraying is always worth a try.

Squash bugs overwinter as adults under plant debris and 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.

Overwintering squash bugs can begin show up in Utah County gardens in May, and egg laying peaks in late May, depending on the spring weather each year. That means it may soon be time to start 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, spray them with horticultural oil, dab 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 one by one, grab any squash bugs that you see and drop them into the bucket. The soap in the water will let the bugs sink and drown. Eggs are laid only by the adults that have overwintered, not by the new bugs that hatch, so every adult 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 happen to find lots of nymphs on a single 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/into the soil with no gaps or openings) using ultra-lightweight insect-excluding row cover or tulle fabric over low hoops 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 bees can pollinate the blossoms.

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

The new generation of squash bugs reaches adulthood in mid- to late summer and spends the last several weeks of the season feeding and building up the fat reserves they’ll need to overwinter. If you find you’re tired of eating squash before the plants are tired of giving you squash, remove the plants to eliminate the late summer food source they need.


Join thousands already receiving our daily newsletter.

I'm interested in (please check all that apply)