There are about three generations a year. They fly readily and migrate into cultivated areas from alfalfa and other crops and from uncultivated lands. Western striped cucumber beetle larvae feed exclusively on cucurbit roots, whereas western spotted cucumber beetle larvae feed primarily on grasses, corn, and legumes, and do not damage cucurbits. They prefer tender, succulent portions of plants, including the flowers, which they may destroy with their feeding. The beetles chew holes in leaves and scar runners and young fruits.
Adults tend to avoid heat and thus feed mainly on the underside of young melons.
After the skin hardens, melons are much less subject to attack. Scarring in the crown of the plant is also typical of adult damage. Feeding on stems of young plants, followed by sustained winds, may result in severe stand reductions making replanting necessary. In some situations, larvae may cause serious injury by feeding on roots, and young plants can be killed. Cucumber beetles also spread squash mosaic virus.