Striped cucumber beetles are emerging from their overwintering habitat in southern Indiana. This pest can damage cucurbit crops in several ways. One that I saw this week is that they can kill young transplants by their direct feeding. Of more critical concern usually is their ability to transmit the bacterium that causes bacterial wilt of cucurbits. Cantaloupes and cucumbers are especially susceptible to this disease. Pumpkins and some of the winter squashes are susceptible when the plants are young. Other squash and watermelons are not affected by the disease. Therefore, based on years of research and experience, we have set the treatment threshold at 1 beetle per plant for cantaloupes, cucumbers, and very young pumpkins and winter squash (less than 3 weeks old). For watermelons, summer squashes, and older pumpkins and winter squashes, the threshold is 5 beetles per plant.
Our research has shown that for cucurbits grown in the greenhouse and transplanted into the field, FarMore® treated seed provide no protection against striped cucumber beetles. For direct seeded cucurbits, FarMore® treated seed will provide about 3 weeks of protection. The use of planting time treatments of Admire Pro® or Platinum® will also provide about 3 weeks of control for transplants, but our research has shown that the lower rates provide control similar to the higher rate. Use of the lower rate will reduce the exposure of bees and other pollinators to neonicotinoid residues in the flowers. The pyrethroid insecticides provide excellent control of cucumber beetles as foliar sprays. However, it should be noted that our research has shown that weekly sprays of pyrethroids have a significant suppressive effect on cantaloupe yield when compared to spraying only when the threshold was reached. Additionally, spraying only when populations exceeded 1 beetle per plant resulted in 2-3 sprays versus 7-10 when sprays were applied weekly.