Squash bugs (Anasa tristis) are one of the most destructive garden pests home gardeners face each year. One day your pumpkins and squash plants are fine, and the next day, they’re a wilted mess. Within a few days, your entire pumpkin patch has been wiped out. Check around the plants for the distinctive shield-shaped body of the squash bug and the bronze-colored eggs. Chances are good they’re hard at work feeding on, and killing, your plants.
Know Your Enemy: The Life Cycle of the Squash Bug
Squash bugs spend the winter hiding under plant debris, such as fallen leaves, dead perennial plants, or old garden vegetables you forgot to clean up. When the weather turns warmer in the spring, adult squash bugs emerge from their hiding spaces and seek mates.
After mating, the female lays her eggs on the leaves of plants in the squash family. Each female lays a clutch of small bronze pellet-shaped eggs on the underside of the plant’s leaves. The eggs are spaced in a V-shape, usually near the veins of the leaf where the leaf and stem join together. Eggs may also be left at the base of plants. Most squash beetles lay about 20 eggs in each clutch. Squash beetle eggs are very distinctive, and easy to spot if you look carefully under the leaves of your plants.
Nymphs hatch from the eggs in about 10 days. When squash beetles are in the nymph stage, they can be hard to detect. The tiny gray nymphs scurry for cover as soon as you get near the plants, probably a protective measure to prevent birds and other creatures from eating them. Once you leave, they emerge to do their dirty work.
It’s during the adult and nymph stages that squash beetles do the most damage to plants. Squash beetles have sucking mouth parts that pierce the leaves and suck out the sap, damaging the leaves. If enough leaves on the plant are damaged, the plant can’t produce enough energy to live, and it will die.
Controlling Squash Beetles
The easiest time to control squash beetles is during the fall, when the beetles are seeking protected places to overwinter, and during the egg stage.
During the late fall, cleaning up garden debris is essential to controlling squash beetles. They can’t survive extremely cold winters. By reducing the number of hiding places for them, you give them less of a chance to survive into the following spring. Rake up fallen leaves, cut back perennial plants, and pull up old garden vegetables at the end of the season. Bag them and put them in the trash rather than composting them to further reduce the number of areas where squash beetles can hide.
Eggs can be removed or, if you’ll pardon the pun, squashed when they’re on the plant. To remove squash beetle eggs, you can use a piece of duct tape to pull the eggs from the leaf. This can damage leaves, so be careful. Another method is to use a butter knife and gently scrape them from the leaves. Scrape them onto a piece of paper and squash them to kill the eggs.
Nymphs are harder to kill, but not impossible. Water forces the nymphs out of hiding, so look for them after you spray your plants with the garden hose. Make a soap trap using an old glass jar, such as a spaghetti sauce jar with a lid. Clean the jar, then add one teaspoon of liquid dish soap. Fill the jar halfway with tap water and mix the soap and water by stirring the liquid once or twice. Bring your jar into the garden and flick the nymphs into the soapy water. They fall in, but can’t squirm out, and drown.
Another organic gardener’s trick to find and kill squash bugs is to use their natural propensity to hide to your advantage, not to theirs. Place a board on the soil or a piece of cardboard. When the bugs go under it, pick it up quickly and squash the bugs, or push them into your soap water mixture. You’d be surprised by how many bugs you can get rid of that way.
If you’re fed up with squash bugs and want a more conventional method of ridding your garden of them, four insecticides are known to kill squash bugs. The University of Minnesota Cooperative Extension lists carbaryl, permethrin, bifenthrin, and esfenvalerate for use against squash bugs. These chemical controls are sold in different products under various brand names; read product labels before purchasing to make sure they’re effective against squash bugs. Whenever you’re using pesticides, read the label carefully. Follow all label directions for safe application, clean up, and packaging disposal.
What If It’s Not Bugs?
You step outside to view your prized pumpkin patch and find the vines shriveled and the leaves gray, but no sign of squash bugs. What’s going on?
A bacterial wilt, Erwinia tracheiphila, may be the culprit. This disease is spread by cucumber beetles, and while not usually affecting pumpkins, it can strike any plant in the same family as squash, melons, cucumbers and pumpkins. Infected beetles feed on emerging plants, causing the telltale wilt. Infected plants can’t be saved, so pull them up and discard them in the trash, not the compost pile. Composting infected plants just spreads the bacteria.
Gardeners are optimists. Each year, we do our best, planting seeds and nurturing them along. In some years, we get a bumper crop of delicious fruits and vegetables. Other years, the bugs get the crop. Beat the bugs this year and squish those squash bugs before they conquer your garden.