NDSU

FLAX:  Linum usitatissimum L.

Insecticide Efficacy Against Adult Grasshoppers on Flax, 2003

Twostriped grasshopper:  Melanoplus bivittatus (Say)
Migratory grasshopper:  Melanoplus sanguinipes (Fabricius)

Registered and experimental insecticides were evaluated for their efficacy at controlling adult grasshoppers and protecting bolls on flax. A field in north central North Dakota near Blaisdell, ND had pretreatment counts of 12 adult grasshoppers/yd² with the majority being twostriped grasshoppers.  Plots were 10 ft wide by 30 ft long. A RCB experimental design with four replicates was used. Insecticides were applied at the green boll stage on 31 July using a handheld CO₂ boom sprayer at 40 PSI, and 10 GPA and fitted with XR 8001 nozzles. Visual counts were conducted in each plot to assess the number of adult grasshoppers/yd² and the number of clipped bolls/ft² on the ground at 1, 4, and 7 DAT. Variables were subjected to ANOVA and means compared using Fisher’s PLSD at the 5% significance level.

The untreated check and low and high rates of Sevin XLR had significantly greater numbers of adult grasshoppers/yd² compared to the other insecticide treatments at 1 DAT. At 4 and 7 DAT, all of the insecticide treatments had significantly lower numbers of adult grasshoppers when compared to the untreated check but were not significantly different from each other. The untreated check and high rate of Sevin XLR had significantly greater numbers of clipped bolls on the ground at 1 DAT compared to both rates of Mustang Max, Proaxis, and Baythroid. The number of clipped bolls for the low rate of Sevin XLR was not significantly different from any treatments at 1 DAT. Differences between insecticide treatments at 4 and 7 DAT were not significantly different from each other in their ability to control grasshoppers or protect bolls, but all treatments were significantly better than the untreated check. Continued movement of adult grasshoppers from untreated areas surrounding plots made further evaluation difficult. Results indicate that the pyrethroid insecticides acted quicker than Sevin XLR to reduce grasshopper numbers and protected flax bolls from being clipped from the stem more effectively following the initial treatment.