Cucumber Beetles

Identification

Adult cucumber beetles measure 1/4″ long at maturity. They are bright yellow with spots or stripes, depending on the species. Their larvae live underground and are seldom seen.

Damage

Adult beetles make small, ragged holes in the leaves and flowers, and transmit bacterial wilt.

Prevention

Only plant bacterial wilt-resistant cultivars, or plant cucumber beetle-resistant varieties such as ‘Saladin’, ‘Little Leaf 19’, and ‘Gemini’ cucumbers, muskmelons, butternut-type squashes, and squashes in the species group Cucurbita moschata as they are less favored by the beetles.

Physical control

As with many other insects listed in this guide to vegetable garden pests, cucumber beetles can be kept off of plants by covering them with floating row cover, but in this case, you’ll need to remove the cover when the plants come into flower to allow for pollination. Mulch susceptible crops with loose materials like straw or hay to prevent egg laying.

Chemical control

It is highly recommended to try physical prevention/control methods before resorting to chemical control. Spinosad-based products may help to manage cucumber beetles. Check local regulations (or your local Extension Office where applicable) to identify which products can be used in home gardens in your area. Follow label instructions carefully for safe and effective insecticide application and to ensure that edible crops are safe to harvest. Test insecticide on a few plants before widespread application. Look for the most selective insecticide to minimize harm to beneficial insects- even some “selective” and "natural" insecticides can still negatively impact beneficial insects. Where possible, apply contact-based insecticides in the late evening and try to avoid spraying during blooming to minimize negative impacts on pollinators- in some cases the insecticide may need to be hosed off in the morning to avoid contact with pollinators. Do not spray spinosad on flowering plants.