Western Striped Cucumber Beetle
Western Spotted Cucumber Beetle
- Leafy Green Crops
Adult western striped cucumber beetles are about 1/3 inches long, with black heads and yellow and black-striped wings. Adult spotted beetles are the same size with 12 black spots on their yellowish wings. Striped cucumber beetle can be a serious pest of cucurbits in Utah, while the spotted cucumber beetle is a minor pest. Adults of both species feed on leaves, but only striped beetles feed on the fruits. Larvae are 1/3-1/2 inch long, with white to yellowish bodies, brown heads, and three pairs of brown legs.
The beetles spend the winter in protected sites near agricultural fields and home gardens (under plant debris, in wooded areas, in crevices of buildings and fence posts, etc.). They become active in spring when temperatures rise above 50°F. They will then feed on pollen, nectar, and blossoms before host plant material is available. Adults can fly long distances (up to 500 miles in high-altitude air currents). They mate in the spring, and females will lay anywhere from 200-1,200 eggs in moist soil at the base of cucurbit plants. In spring and early summer, larvae feed exclusively on the roots. Later, they will also feed on the rinds and flesh of cucurbit fruits. Larvae require about 15 days to complete development. The pupae are white to yellow in color, and about 1/4 inch long. They look like a soft-bodied adult without wings. Two summer generations of adults occur in northern Utah.
- Feeding scars on soft rinds of fruits, especially the undersides
- Holes in stems and leaves
- Destroyed flowers
Monitoring is a critical part of any cucumber beetle management strategy. All above-ground parts of the plant should be checked regularly, including the underside of leaves and base of the stems. Newly emerged or transplanted cucurbits should be scouted two or three times per week, since beetle feeding can rapidly kill small plants. Weekly scouting is sufficient after plants become larger. Control measures are warranted on mature plants if five or more beetles per plant are present. On young plants, control is needed if unacceptable feeding damage is observed.
Use of row covers in spring, mulches near the base of stems, hand-removal of beetles, drip irrigation, and destroying crop residue in the fall can reduce cucumber beetle populations and crop damage. If there is a history of cucumber beetle problems in the area, planting non- and less- preferred cucurbit species and varieties can help the home gardener avoid beetle infestations.
In addition to direct feeding injury, cucumber beetles vector plant diseases, such as bacterial wilt, squash mosaic virus, and others. Bacterial wilt has not been detected in Utah, but squash mosaic virus does occur.
Insecticides can be effective for control of cucumber beetles, but should not be used as the first or sole management tool. Click here to view insecticide options.