Champion Daylilies
Cucumber Beetles
Cucumber beetles are about 0.36 inch (9 mm) long and either have a greenish yellow background with black spots or alternating black and yellow stripes. They fly readily and migrate into cultivated areas from alfalfa and other crops and from uncultivated lands. Cucumber beetles like moisture and dislike heat. Consequently, melon fields are especially attractive in hot weather during and after an irrigation.
Damage
Cucumber beetles are serious pests of smooth-skinned cucurbits, especially melon varieties such as honeydew, crenshaw, and casaba. 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.
Management
Damaging populations of cucumber beetles are usually treated with insecticides.
Biological Control
Cucumber beetles are attacked by a variety of natural enemies, the most important being a parasitic tachinid fly, Celatoria diabroticae. Natural enemies are rarely effective enough, however, to reduce populations below economically damaging levels.
Cultural Control
There are no effective cultural controls for these pests. Because spotted cucumber beetle larvae also feed on corn, avoiding planting cucurbits next to corn may help some.
Monitoring and Treatment
Cucumber beetles are difficult to control. Sprays must be directed at adult beetles. Larvae of western spotted cucumber beetle develop outside of cucumber fields. Striped cucumber beetle larvae are located on roots where they cannot be controlled.
Treatment of adults may be necessary if there is an average of one beetle a plant during the seedling-to-4-inch-tall stage. Infestations that develop late in the season are usually not as damaging as those that begin earlier because the population levels tend to be lower. Apply treatments before beehives are introduced into the field; typically, treatment is often made the day before bees are put in the field.
Spotted
Striped