Impact of Insecticide Strategies and Varieties on Control of the Crucifer Flea Beetle in Canola.
Janet Knodel, Bryan Hanson, Robert Henson, and Denise Olson. North Dakota State Univ, Dept of Entomology, Hultz Hall, Fargo, ND 58105
Phyllotreta cruciferae, crucifer flea beetle, is an important insect pest of spring-planted canola, especially during the seedling stage. Different varieties of canola, Brassica napus, were evaluated: ‘225’ open pollinated, ‘357’ hybrid Round-up Ready line, and ‘4870’ Liberty Link InVigor line. Two commercially available Seed Treatments (ST) were evaluated at their low and high rates of insecticide active ingredient: thiamethoxam (Syngenta Crop Protection) and clothianidin (Bayer CropScience). Bifenthrin (FMC Corporation) was also evaluated as a foliar-applied insecticide. Each variety was grown using the following treatments: untreated check, bifenthrin applied once, bifenthrin applied twice, low rates of thiamethoxam and clothianidin ST, low rates of thiamethoxam and clothianidin ST plus bifenthrin applied 21 days after planting, high rates of thiamethoxam and clothianidin ST, and high rates of thiamethoxam and clothianidin ST plus bifenthrin applied 21 days after planting. During spring of 2004 and 2005, the cool wet weather caused a prolonged delay in flea beetle emergence and undesirable feeding conditions, and this resulted in lower infestations in canola. Results indicate that plant stand counts were affected more by variety differences than insecticide treatments. Percent of plants injured by flea beetles and injury ratings were influenced more by insecticide treatments. In general, the high rates of STs and high/low rates of STs plus a foliar spray had a lower injury from flea beetles than low rates of STs, foliar-applied insecticide and the untreated check. Differences observed in crop phenology measurements, like flowering dates, maturity dates, and crop height, were primarily attributed to differences in variety. Yield, kernel weight, and percent oil were influenced by variety and insecticide treatments, to a lesser extent. In summary, variety selection and insecticide treatments are important factors for producers to consider for control of crucifer flea beetles on canola.