Insects become active when temperatures in Spring start to rise. Many of the first insects seen are those that overwinter as pupae or adults. The striped cucumber beetle, Acalymma vittatum, overwinters as an adult. Once the temperatures reach the 60s, the adults will break diapause (a dormant overwintering state) and become active. Like most beetles, striped cucumber beetles will feed on pollen from a variety of plant sources. Yesterday (April 24, 2011) I noted numerous striped cucumber beetles feeding on crab apple pollen.
The striped cucumber beetle is an important pest of cucumber. Early in the season, it damages plants by feeding on the foliage, stems and roots. It can also transmit bacterial wilt, Erwinia tracheiphilia, a disease that harbors in the bodies of overwintering beetles. The bacteria infects the plants when the beetles defecate onto feeding sites. The bacteria invades the plant vascular system and blocks transport of water, causing the plant to wilt and die.
We associate striped cucumber beetle with cucumber. The beetles overwinter on the edges of the fields and will commonly find cucumbers planted early in the season. However, the adults become active early in the spring. If suitable host plants are not locally available, the beetles may disperse to search for a new home. We find them foraging on pollen along the way.