Cucumber beetles are the primary vector of bacterial wilt. Even a fairly low population of beetles can spread this disease across the field. Once infected, there is no cure for this disease. Plants will rapidly wilt and die, effectively reducing the plant stand and the yield potential. Cucumbers are the most susceptible to bacterial wilt followed by melons, pumpkins and zucchini.
The cucumber beetle spray threshold is 1 beetle per plant. Inspect 100 plants across the field and divide the number of beetles by 100 to determine the average number of beetles per plant. Cucumber beetles are most active in the early morning hours. They often hide in the soil during the heat of the day. Population assessments done in the middle of the day may not be representative of the actual number of beetles in the field.
For more information on cucumber beetles and bacterial wilt, visit Ontario Crop IPM at http://www.omafra.gov.on.ca/IPM/english/cucurbits/index.html