Crucifer and stripped flea beetles have emerged from overwintering sites in shelterbelts and have been observed in canola fields in Langdon and Minot (L. Lubenow & A. Chirumamilla, LREC; T. Prochaska, NCREC). The adult crucifer flea beetle is a small (⅛ inch long), oval-shaped, blackish beetle with a bright blue sheen on their wing covers. The adult striped flea beetlesare similar in size and shape to the crucifer flea beetle, but they are black with two yellow strips on their wing covers. Flea beetles have enlarged hind femora (thighs) on their hind legs, which they use to jump quickly when disturbed. Their name, flea beetle, arose from this behavior. Adult flea beetles feed on the cotyledon and true leaves causing pitting and defoliation, and are usually active until the end of June.
The economic threshold is 25% defoliation in the seedling to 6-leaf stage for a rescue foliar treatment. However, economic populations have not been observed yet. This is a good time to start scouting for flea beetles in canola to ensure that the insecticide seed treatment is working and protecting against adult feeding injury. Insecticide timing is very important and rescue foliar treatments should be applied as soon as possible. Apply insecticides during the sunny, warm part of the day when beetles are actively feeding on the plants. Canola plants that have reached the 4-6 leaf vegetative growth stage or beyond can tolerate more feeding damage, unless flea beetles are damaging the growing point (center stem). Insecticides registered in canola are available in the 2016 ND Field Crop Insect Management Guide.
Janet J. Knodel, PhD
Extension Entomologist & Associate Professor
NORTH DAKOTA STATE UNIVERSITY