The squash bug is primarily a garden pest, but because it can overwinter in the walls of buildings, it can become a nuisance when it moves into the home seeking warmth and shelter as the weather turns cold. Once inside, the bugs can stay active throughout the winter, but they do not cause damage to homes or houseplants.
The squash bug can be identified by several characteristics. It is just over 1/2 inch long and has a squat, wide body with grayish-brown coloring and brownish-orange stripes along the edges of its back and on its underside. It has wings and can fly, but it is most commonly found scurrying along plants, and it can move quickly in evasion. When crushed, it emits an unpleasant odor, much like its near lookalike, the stink bug.
Squash bugs are common in vegetable gardens, as they feed on pumpkins, squash (thus their name), and related plants. The beetles feed on the plants by sucking out the juices, causing the leaves to lose water and nutrients, then they wither and brown. Large healthy plants typically are not endangered by squash bugs, but high populations can kill smaller plants or cause any plants to lose runners. The bugs may also feed directly on the fruit of the plant, damaging or possibly killing the squash or other fruit.
3 Ways to Get Rid of Squash Bugs
Most control methods for squash bugs involve hunting or trapping and killing the bugs, at all life stages. You can also control them with spray insecticide, but this is often no less trouble than manual removal.
Hunt and Trap Them in the Garden
Garden control should take place during the spring and summer as the plants grow. Squash bugs become active and lay their eggs in early spring. It's best to eliminate the bugs at this stage, before the eggs develop into nymphs and adults, which are more difficult to catch and kill.
Inspect the undersides of plant leaves for eggs and nymphs, preferably each morning. Eggs are typically laid in groupings of about 20, often near junctures of stems. Crush any eggs that you find. If you find nymphs (which are small and spider-like, with green bodies and black legs) or adults, remove them from the plant and drop them in a container of soapy water to kill them.
A simple trap can be effective for adult squash bugs: Place a board or wood shingle flat onto the ground near vulnerable plants, or between plant rows. Leave the board overnight; adult squash bugs will seek refuge under it. First thing in the morning, turn the board over and capture and dispatch the bugs. Alternatively, you can place the board onto another board or other hard, flat surface, and squash the bugs between the boards (just beware of the odor emitted when the bugs are crushed).
Because squash bugs can fly, they can migrate from other yards or gardens, so inspection and control must continue through summer. Squash bug damage to plants diminishes in late summer and fall.
Vacuum Them Up in the House
Like the boxelder and stink bugs, squash bugs crawl into cracks and crevices in a house or other structure and seek shelter inside the walls. When the weather turns cold, they migrate into the home, where they typically move around individually rather than congregating in groups. The best way to control them in the home is to suck them up with a vacuum, either a standard one or a shop vac. It's best to use a vacuum bag (many shop vacs can be fitted with bags) for easy disposal.
If you want to kill the bugs manually, avoid smashing or crushing them indoors, due to the resulting odor. Squashing them in place also can stain the underlying surface: furniture, carpet, walls, etc.
Spray Them if Necessary
Various insecticides are effective on squash bugs, including organic treatments such as neem oil and horticultural oil. Chemicals such as permethrin, acetamiprid, and malathion are also effective but not necessarily better than organic options. Chemicals also tend to be more harmful to bees and other pollinators, so it's best to stick with organic treatments.
Insecticides are most effective on squash bug eggs and nymphs and may have little or no effect on adults. In early spring and throughout summer, spray the undersides of leaves with your chosen treatment following the manufacturer's directions; spraying from above does little good because it doesn't reach the bugs.
Neem oil and other organic insecticides are not completely nontoxic and can harm bees and other pollinators. To minimize this risk, apply insecticides only at night or early in the morning, when flowers are closed and bees are less likely to be foraging. Follow directions carefully to avoid improper application, which can be harmful to bees and other wildlife.
What Causes Squash Bugs?
Adult squash bugs overwinter under cover of leaves, dead plant foliage, and yard debris as well as inside structures. They emerge in spring to mate and lay eggs. Nymphs hatch from the eggs in approximately 10 days and mature to adulthood in four to six weeks. Fortunately, squash bugs typically have only one hatch per year.
Squash bugs are attracted to several plants in the cucurbit family:
How to Prevent Squash Bugs in Your Home and Garden
To keep squash bugs out of your garden and away from your plants, tidy up in the garden and around the yard throughout the summer and, especially, in fall. Remove dead plant material, particularly from cucurbit plants, and clean up leaves and yard debris. The goal is to eliminate places where squash bugs can overwinter.
As with most pest problems, keeping your plants in top condition makes them less attractive squash bugs and less vulnerable to significant damage. Rotating crops from year to year helps prevent recurring squash bug infestations. You can also choose resistant varieties of squash, such as butternut and royal acorn squash, and sweet cheese pumpkins. Watermelons, cucumbers, and muskmelons are relatively resistant to squash bug damage.
To help prevent a home invasion of squash bugs, inspect the home exterior to find and seal all cracks and openings to prevent the bugs from entering. Caulk around incoming pipes, utility wires, and cables. Repair window and door screens, and ensure door and window seals are intact.
Squash bugs can also be brought in on firewood. To prevent this, don't store firewood in the home or near exterior walls. When the wood is brought in, use it as soon as possible so any insects in or on the wood don't end up in your home instead.
Squash Bugs vs. Stink Bugs and Boxelder Bugs
Squash bugs share some physical and behavioral characteristics with stink bugs (particularly the brown marmorated stink bug, or BMSB) and the boxelder bug. Boxelder bugs can be distinguished from stink bugs by the red lines on the boxelder's body and wings. When at rest, the red lines on the folded wings form an upside-down V. This common pest feeds on boxelder trees.
The stink bug is wider and rounder than the squash bug. It also gives off an odor when disturbed as well as when crushed, thus its name. The stink bug is more likely to attack tomatoes and beans as well as fruiting plants than it is to feed on squash.
Frequently Asked Questions
Do Squash Bugs Spread Disease?
Squash bugs do not carry or spread human or plant diseases. The damage they cause to plants can look like damage from cucumber beetles resulting from a disease known as bacterial wilt, but squash bug damage is merely physical, not biological.
Do Any Plants Repel Squash Bugs?
Some gardeners report success with companion-planting nasturtium (Tropaeolum spp.) or tansy (Tanacetum vulgare) next to squash or similar plants that are vulnerable to squash bugs. In general, companion planting is not a reliable deterrent technique, but it never hurts to try.
Do Dead Squash Bugs Attract More Bugs?
It is a common misconception that crushing stink bugs attracts other stink bugs. This is not true of stink bugs, nor it is true of squash bugs. You do not have to worry about where you place dead squash bugs or their eggs.