Populations of the overwintering generation of striped cucumber beetles are just about at their peak levels right now (Figure 1.). For muskmelons and cucumbers, this generation is the one that we worry the most about in terms of transmitting the pathogen that causes bacterial wilt. As a result, our spray threshold is relatively low, 1 beetle per plant. Watermelons and most squashes and pumpkins are not susceptible to bacterial wilt so we use a higher threshold, 5 beetles per plant. The pyrethroid insecticides provide excellent control. Because these insecticides are harmful to pollinators, growers should wait until late afternoon or evening when the flowers have closed and the pollinators have left the field before spraying.
Figure 1. Striped cucumber beetle (Photo by Wenjing Guan)