Insecticide Efficacy against Grasshopper Nymphs on Barley, 2004

Janet J. Knodel, Area Extension Specialist–Crop Protection

Lorilie Atkinson, Research Specialist

North Central Research and Extension Center

Two-striped grasshopper: Melanoplus bivittatus (Say)

Migratory grasshopper: Melanoplus sanguinipes (Fabricius)

Experimental insecticides were evaluated for their efficacy at controlling nymph stage grasshoppers and protecting barley, cultivar Robust. A field in north central North Dakota near Maxbass, ND had pretreatment counts of >20 nymphs (1-4 instars) grasshoppers/yd² with the majority being twostriped grasshoppers.  Plots were 10 ft wide by 30 ft long. A RCB experimental design with three replicates was used. Insecticides were applied at 60 Zadoks scale on 7 Jul using a handheld CO₂ boom sprayer at 40 psi, 10 gpa and fitted with XR 8001VS nozzles. Ten flag leaves were assessed per plot for the percent defoliation at 7, 14, 21, and 28 Days After Treatment (DAT). Yield was calculated using the following formula to estimate bushels per acre:

                   {((Heads/ft² x Avg. # of Kernels/head) x 43560)/14,300 kernels/lb}

                                                                        48 lbs/bu

Variables were subjected to ANOVA and means compared using Fisher’s PLSD at the 5% significance level. All of the insecticide treatments had significantly lower percent defoliation than the untreated check at 7 and 14 DAT, except for Sevin XLR at 14 DAT. Differences between insecticide treatments at 7 DAT were not significantly different from each other in their efficacy to control grasshoppers. At 14 DAT, Warrior applied at 3.2 fl oz/acre + crop oil and Danitol applied at 10⅔ fl oz/acre had significantly lower defoliation than Sevin XLR. Otherwise, insecticide treatments were comparable at 14 DAT. At 21 and 28 DAT, the defoliation increased slightly as grasshoppers continued to move into plots to feed and as insecticide residue was diminished. At 21 DAT, all insecticide treatments continued to provide protection except for Sevin XLR. At 28 DAT, Sevin XLR and Mustang Max applied at 2.8 fl oz/acre were not significantly different from the untreated check.  All other insecticide treatments continued to provide adequate protection up to 28 DAT. Although the untreated check had a lower yield than the insecticide treated plots, these yield differences were not significantly different among treatments. With the exception of Sevin XLR, results indicate that insecticides tested were able to reduce grasshopper numbers and protect barley up to 28 DAT.

Means within a column followed by the same letter are not significantly different (ANOVA, Fisher’s PLSD, P<0.05).

Part II.  Materials Tested for Arthropod Management

Insecticide Efficacy against Grasshopper Nymphs on Barley, 2004

^a Yield was estimated using formula including number of heads in square foot and average number of kernels per head.

Last Updated: Tuesday, July 05, 2005 10:26:36 AM
Published by North Dakota State University