Comparative evaluation and economic potential of ecorational versus chemical insecticides for crucifer flea beetle (Coleoptera: Chrysomelidae) management in Canola.

From 2001 to 2004, field studies were conducted to evaluate the effect of the ecorational insecticides SpinTor (spinosad), BotaniGard (Beauveria bassiana), Neemix (azadirachtin), and Surround (kaolin) against crucifer flea beetle on canola, Brassica napus L., at the cotyledon stage. The ecorational treatments were compared with a standard foliar chemical insecticide, Capture (bifenthrin), and the chemical seed treatment insecticide Helix XTra (thiamethoxam). This study indicated that flea beetle injury was lower for Helix XTra, Capture, and the ecorational insecticide SpinTor. SpinTor was less effective when flea beetle populations were relatively high (200-300 per trap-week). Yields for chemical insecticide treatments were always greater than SpinTor, with differences being the smallest (68-374 kg/ha) at low levels of flea beetle feeding injury. Differences were greatest when canola seedling injury was high (775-1,364 kg/ha). Yield differences between the conventional insecticides and BotaniGard, Neemix, and Surround were 119-439 and 61-2,248 kg/ha at low and high flea beetle feeding injury, respectively. Although yield differences between SpinTor and chemical insecticides were relatively small at lower levels of flea beetle injury, net losses ranged from $47 to $151/ha when SpinTor was used as an alternative to a standard chemical seed treatment, Helix XTra. This suggests that SpinTor would not be a viable alternative to the chemical insecticide. Net losses ranged from $30 to $266/ha when BotaniGard, Neemix, and Surround were used as alternatives to the seed treatment.

Distribution and Severity of Pasmo on Flax in North Dakota and Evaluation of Fungicides and Cultivars for Management.

Pasmo, caused by Septoria linicola, reduces flax (Linum usitatissimum) yield in the Canadian provinces of Manitoba and Saskatchewan, but little is known about its distribution and effect on yield in North Dakota. Field surveys for pasmo were conducted in 74 and 87 flax fields across 19 and 23 North Dakota counties in 2002 and 2003, respectively. The surveys indicated that pasmo was present in 17 and 18 counties in 2002 and 2003, respectively. County mean plant incidences ranged from 0 to 21% and 0 to 84.5% in 2002 and 2003, respectively. County mean pasmo severity ranged from 0 to 38.8% and 0 to 29.3% in 2002 and 2003, respectively. Significant (P ≤ 0.07) positive Pearson correlations were detected between total rainfall accumulated for June to August and pasmo severity in 2002 and 2003 and for rainfall and pasmo incidence in 2003. Field trials were conducted to determine the effect of fungicides and flax cultivars on pasmo severity and flax yield. Pasmo severity was significantly (P ≤ 0.05) reduced with azoxystrobin and sulfur fungicides compared with the untreated control. Flax yields were significantly (P ≤ 0.05) greater in azoxystrobin- and prothioconazole-treated plots than in the untreated control plots. Cv. Omega had significantly lower pasmo severity than the other three cultivars, but cv. Rahab 94 had the greatest yield of all the cultivars. Based on the results presented, pasmo is an important disease of flax in North Dakota, and its distribution is widespread throughout the flax-production region. Fungicides such as azoxystrobin and prothioconazole appear to be excellent potential tools for pasmo management.