University of Illinois Extension
Bruce Spangeberg

These articles are written to apply to the northeastern corner of Illinois. Problems and timing may not apply outside of this area.

Stateline Yard & Garden

Cucumber Beetle a Major Garden Pest

May 18, 2000

Cucumbers and melons are popular crops in the home vegetable garden. Probably the biggest enemy of these crops is an insect called the cucumber beetle. Although actually a small insect, it may cause considerable damage to these crops.

There are actually two types of cucumber beetles, the spotted and the striped. Both are small beetles, less than 1/4 inch long and yellow-green in color. The striped cucumber beetle is most common in our area, and has three black stripes down its back. (The spotted has 12 black spots.) Flip it over and the rear portion of the underside should be black. If it's yellow, it's the western corn rootworm beetle, not considered a serious pest of cucumbers or melons.

Cucumber beetles spell trouble for cucumbers and related plants in two ways. First, they directly consume leaves, which is especially a problem when plants are small. Even more damaging, however, is the fact cucumber beetles can carry bacterial wilt disease, a serious problem of cucumber, muskmelon, and watermelon. Infected plants suddenly wilt and die after the beetles have been feeding.

Cucumber beetles start feeding early in the season; often eating plant leaves just emerging from the soil. If the beetle is carrying the bacteria, the plant becomes infected. Symptoms may not show until later into the season, when the vines wilt and die.

As garden plantings are made, watch for the cucumber beetle. Control by applying either carbaryl (Sevin) or rotenone. Reapply at weekly intervals if beetles are still present.

Once the plants start to bloom, apply late in the day and keep the insecticide off the blooms to avoid contact with bees and other pollinating insects.

Another early season control option is to use a polyester row cover. Put the cover over cucumbers and melons, making sure to seal the edges into the soil. Look carefully around the plants before doing this, however, to assure there are not any cucumber beetles present that could be trapped under the cover! Also, once the plants start to bloom the cover needs to be removed so pollinating insects can get to the flowers.


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