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Canola Flea Beetles Still Hungry! (06/07/18)

As reported in the May 24th issue of the Crop & Pest Report, field monitoring for flea beetles and their feeding injury (defoliation, pitting in cotyledons/true leaves) is crucial when populations can increase rapidly with warm, calm and sunny days.

Canola Flea Beetles Still Hungry!

As reported in the May 24th issue of the Crop & Pest Report, field monitoring for flea beetles and their feeding injury (defoliation, pitting in cotyledons/true leaves) is crucial when populations can increase rapidly with warm, calm and sunny days. Field reports from northeast and north central areas of North Dakota indicate that flea beetles are aggressively feeding on canola. In some instances, fields were completed destroyed from flea beetle feeding injury and will be need to be reseeded. Residual on the insecticide seed treatments is no longer effective against these late emerging flea beetles, so scouting for these hot spots is essential. Beetles will be actively feeding for two more weeks and then start to decline by late June.

For foliar insecticide applications, the action threshold is when an average of 20-25% defoliation on the cotyledons and/or first true leaves, and beetles are actively feeding in field. Foliar treatments must be made quickly, if defoliation exceeds 20-25%. Under high beetle densities, a delay of one to two days can result in the loss of an entire field. Apply insecticides during the sunny, warm part of the day when beetles are active. Canola plants that have reached the 4- to 6-leaf vegetative growth stage or beyond can tolerate more feeding injury.

Pyrethroid insecticides (a.i. bifenthrin, deltamethrin, gamma-cyhalothrin, zeta-cypermethrin) provide good control of flea beetles and a 7-10 day residual at the high-labeled rate. If it is hot (above 85⁰F), pyrethroid insecticides break down faster and are not as efficacious controlling insect pests. So, insecticide application may need to be applied early in the morning or in the evening when it’s hot. Insecticides registered for flea beetle management in canola are listed in the 2018 North Dakota Field Crop Insect Management Guide E1143.

For more information, please consult the NDSU Extension fact sheet Integrated Pest Management of Flea Beetles in Canola E1234 (revised).

knodel.1

 

Janet J. Knodel

Extension Entomologist

 

T.J. Prochaska

Ext. Cropping Systems Specialist/NDSU NCREC

 

Lesley Lubenow

Area Ext. Specialist/Agronomy NDSU LREC

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