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Canola Flea Beetles Feeding Activity Increasing

Posted: Jun 09 2022

The recent stretch of dry, warm sunny weather has flea beetles hoppin’ and poppin’ in canola! Scout canola fields now and regularly in the next few weeks for flea beetle feeding, especially in canola from the cotyledon through 6-leaf stages. The higher the feeding pressure, the more frequently fields should be scouted. The cool, wet weather we had in mid-May in most of ND either delayed canola planting or slowed growth of canola that did get planted. Consequently, canola is in early growth stages that are most susceptible to flea beetle feeding injury. Insecticide seed treatment failure is a possibility, especially in earlier planted canola that experienced delayed growth. Economic feeding injury to seedlings will result in delayed plant development for the remainder of the growing season. In the photos, note that the protected seedling is already at 1-leaf, while the untreated seedlings are still in the cotyledon stage.

When scouting, look for the presence of striped and crucifer flea beetles, and examine the cotyledons and emerging leaves closely for pitting and shotholes. Make note of which species is most dominant – current NDSU research has demonstrated that striped flea beetles are not as well controlled by neonicotinoid and diamide seed treatments as compared to crucifer flea beetles. A flea beetle population dominated by striped flea beetles could cause greater and more rapid seedling injury than a population dominated by crucifer flea beetles. A foliar treatment is warranted if 20-25% defoliation has occurred on seedlings through the 6-8 leaf stage. Foliar insecticides for flea beetle control in canola are limited to the pyrethroids: bifenthrin (Brigade, Sniper, other 2 lb. bifenthrin products), deltamethrin (Delta Gold), lambda-cyhalothrin (Silencer, Warrior II, other 1 and 2 lb. lambda-cy products), zeta-cypermethrin (Mustang Maxx) and two premixes - bifenthrin + sulfoxaflor (Ridgeback) and lambda-cyhalothrin + chlorantraniliprole (Besiege). Keep in mind that new growth after application will not be protected, so scouting after a foliar application is a must.

Initial results from our insecticide seed treatment trials here in Fargo look promising so far. Canola was seeded on May 23 and is in the cotyledon to 1-leaf stage as of June 6. Flea beetles are feeding, and our Fargo population is about 75% striped flea beetle, and 25% crucifer flea beetle. We’re testing commercial rates of thiamethoxam (Helix) alone and in combination with cyantraniliprole (Lumiderm, Fortenza), and clothianidin (Prosper) alone, in combination with cyantraniliprole and in combination with flupyradifurone (Buteo Start). Initial feeding injury ratings show that all seed treatments are performing well with no significant differences among treatments. However, we did note slightly more feeding injury when thiamethoxam and clothianidin were used alone compared to those same actives in combination with either cyantraniliprole or flupyradifurone. The untreated check plots are well past threshold. Ratings will be done every three days to evaluate continuing insecticide seed treatment performance. For more information, please consult NDSU Extension publication E1234 (revised) - Integrated Pest Management of Flea Beetles in Canola, and E1143-22 - North Dakota Field Crop Insect Management Guide for a list of insecticides for flea beetle control registered for use in canola.

Patrick Beauzay -  Research Specialist, Extension Entomology, State IPM Coordinator
Janet J. Knodel Extension Entomologist

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