If you have cucumbers, squash, pumpkins, or melons, you have likely encountered squash bugs on your plants. These flat, large insects are about 5/8 inch long and 1/3 inch wide. They are usually dark brown to dark gray and have a diamond shaped shield on their shoulders. Their abdomens protrude and are typically orange and brown striped.
The eggs of the squash bug are oval, small, and yellowish to bronze. The nymphs, or babies, go through five stages of growth, or instars, and are green when born. They gradually get darker as they mature.
Squash bugs pierce the leaves of your plants and suck the juice out of them. This causes yellow spots that eventually die and turn brown. It also deprives the plant of some of its water and nutrients, which can cause the plant to wilt. Young plants may die from a heavy infestation of squash bugs. Older plants are better able to tolerate the damage, but can also die if the infestation is very heavy.
Squash bugs can be controlled with cultural, physical, and insecticidal methods. Cultural methods refer to keeping your plants as healthy as possible so that they can repel or survive an attack by squash bugs. Physical refers to removing the nymphs and adults and dropping them in a pan of soapy water. This kills the bugs. This is particularly effective if only a few plants are effected or you have only a light infestation.
Placing a piece of cardboard in the rows between squash plants can act as a trap for the squash bugs. They will hide under the cardboard at night and can be destroyed early in the morning. Removing plant debris and other items squash bugs can hid in at night will help keep them to a minimum, as well.
Finally, if you cannot get rid of the squash bugs and they are inflicting significant damage on the plants, you can spray to control the bugs. Squash bugs found early in the spring or summer need to be managed if there are a lot of them. Squash bugs found late in the summer or fall have finished feeding and do not need to be controlled.
The best time to apply the insecticide is early in the morning or late in the evening, when bees and other beneficial insects are not active. It is important to cover the undersides of the leaves with the insecticide, as that is where the bugs congregate.
Effective sprays for squash bugs are ones that contain the ingredients carbaryl, permethrin, bifenthrin, or esfenvalerate. Be sure you read all package labels and only use the insecticide on plants mentioned on the label.