The beetles most often found on zucchini plants are usually a type of cucumber beetle from the diabrotica genus of insects. These yellow beetles feature black spots or black stripes on their backs. An infestation of beetles on your zucchini plants devastates the crop not only because of the damage the beetles do themselves, but because these bugs harbor a type of bacteria that causes squash plants to wilt. Early detection and prevention provide the best way to get rid of beetles on zucchini.
Avoid planting zucchini in the same spot every season. Beetles lay their eggs in the soil where they survive during the winter. Hatchlings will eat and destroy any new zucchini seedlings before they have a chance to take off.
Delay planting zucchini until late spring or early summer, and plant seedlings instead of seeds. Most young beetles will have hatched and moved on by early summer, and any remaining beetles are less likely to destroy larger, established plants.
Cover young plants with floating row covers until they start to flower, especially if you have had problems with beetles in past seasons. The covers protect the plants until they are large enough to withstand pests.
Place yellow sticky traps (available at garden stores) near your zucchini plants. The yellow color and sticky substance on the traps attracts the insects away from the zucchini.
Check your young zucchini plants for beetles, larvae, and eggs twice a week. Examine the plants carefully, especially the undersides of leaves. Manually remove any pests you find and kill them.
Rub the zucchini plants’ stems and leaves gently with cut garlic clove halves to prevent beetles from returning. If you have a larger number of plants, spray them with insecticidal soap according to the manufacturer's instructions.