Control of Crucifer Flea Beetle in Canola through Insecticide Strategies and Canola Varieties
Janet Knodel, North Dakota State University - $26,400

The crucifer beetle, Pyllotreta cruciferae Goeze, represents a major insect threat to canola production wherever it is grown in the Northern Great Plains. This problem will most likely intensify as canola continues to be an important commodity crop. Flea beetles can invade and reduce newly emerged plant stands within a few hours. Currently, the most effective management measure is the use of insecticides to control the overwintering generation of flea beetles as it emerges early in the spring. The seedling stage is the most critical period, and insecticides often need to be applied as a seed treatment or as a foliar application to protect the crop from flea beetle damage.

Although flea beetle populations have decreased slightly in 2004, populations have been at damaging levels since 1997 in central North Dakota , and appear to be increasing based on trapping records. Although post-emergence foliar insecticides can be effective, they require timely applications within a relatively small window of opportunity. Therefore, seed treatments are obviously more convenient. In recent springs, the effectiveness of seed treatments has been questioned. This has often occurred when the seed lies in the ground for 7-14 days before emerging, and flea beetles have a long activity period from late May to June.

As a result, foliar insecticide sprays have been applied over the top of our seed treatment at 21 days after planting. Unpublished data also indicated that flea beetle damage is affected by different canola varieties (seed sizes) and rate of seed treatments. Some of the differences observed in flea beetle feeding injury may be due to differences in variety vigor.

Objective:
1. Compare the efficiency of different insecticide strategies in contrasting canola varieties for control of the crucifer flea beetle at several sites in North Dakota.