Cucumber beetles are nasty little pests that attack cucumbers and related plants (squash, melons, pumpkins) throughout the growing season. The beetles look like 1/4-inch-long insects that are yellow-green in color with a series of black stripes or spots. Watch for them from spring to fall.
They typically eat holes in the leaves and hide out on the bottom side of the foliage. Their green color makes them difficult to detect.
You may first notice them in spring; the beetles eat the leaves of your seedlings. The adults lay eggs near the plants; the eggs hatch into a colony of tiny grubs that eat the plant roots. The adults will also eat leaves and flowers on adult plants.
If that's not bad enough, the pests also carry and spread a disease called bacterial wilt. Plants infected with the disease begin to wilt and die. If you cut a leaf from the plant and look closely, you may see a stringy white substance (that looks like mucus) where you cut off the leaf.
Controlling Cucumber Beetles
Row covers: Protect plants with floating row covers in early spring. These row covers create a barrier that keeps the insects out but allows air, light, and moisture to reach the plants. Be sure to remove the row covers when your vegetable plants grow too large or when the temperatures heat up in summer.
Hand picking: If there aren't a lot of cucumber beetles, picking them off by hand and dropping them in a bucket of soapy water is a safe, budget-friendly means of control.
Clean up in fall: Keep your vegetable garden clean. The pests often overwinter in garden debris -- so composting all dead foliage at the end of the season and tilling the garden each fall will help keep the pest under control.
Attract beneficial insects: Planting flowers, such as marigolds, calendula, sunflower, daisy, alyssum, or dill nearby can attract beneficial insects that attack and eat cucumber beetles.
Insecticidal soaps: Insecticidal soaps will kill the beetles, but must be applied on a regular basis in heavy infestations.
Insecticides: A number of insecticides also effectively kill cucumber beetles. Be sure to follow the package directions carefully.