D3098: Evaluating canola and mustard responses to flea beetle damage and yield

Canola (Brassica napus L.) and mustard species (e.g., Sinapis alba and B. juncea) are economically important oilseed crops in North America. In the Pacific Northwest, flea beetles (Coleoptera: Chrysomelidae) are major pests affecting growth, development and yield. Flea beetle feeding on cotyledons can cause up to 35% yield loss. However, limited research has examined how different cultivars respond to flea beetle damage. We evaluated the susceptibility of canola and mustard cultivars to flea beetle injury. Field trials were conducted in 2024 and 2025 in Moscow, Idaho, using a split-plot design with foliar spray (lambda cyhalothrin (2 fl oz/acre; treated vs untreated) as the main plot and cultivar as the subplot, replicated four times. Sprays were applied twice. The six cultivars tested included three canola cultivars (CP9978TF, CS2600.CR-T, DynaGro280CL), one industrial rapeseed (Industrious), and two mustards (IdaGold: S. alba and Pacific Gold: B. juncea). All cultivars were seed treated with Helix Vibrance (23 fl oz/ 100 lbs seed; thiamethoxam rate 0.404 lbs + fungicides). Industrials were also tested without seed treatment, resulting in seven total treatments. Flea beetle damage was assessed weekly for four weeks by estimating the proportion of leaf area damaged on cotyledons and young leaves (20 seedlings/plot). Foliar spray significantly reduced damage across cultivars, though efficacy varied; CS2600.CR-T and DynaGro280CL performed best. Combining foliar insecticide and cultivar selection effectively reduced flea beetle impact in canola. For Industrious, the combination of seed and foliar treatment was effective, indicating its significance in flea beetle management.