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Insecticide Efficacy against Grasshopper Nymphs on Sunflower, 2004
Janet J. Knodel, Area Extension Specialist – Crop ProtectionLorilie Atkinson, Research Specialist North Central Research and Extension Center
Twostriped grasshopper: Melanoplus bivittatus (Say) Migratory grasshopper: Melanoplus sanguinipes (Fabricius)
Registered and experimental insecticides were evaluated for their efficacy at controlling nymph stage grasshoppers and protecting sunflowers. A field in north central North Dakota near Souris, ND had pretreatment counts of >2 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 V2 crop stage on 19 June using a handheld CO2 boom sprayer at 40 psi, 10 gpa and fitted with XR 8001VS nozzles. Ten plants were assessed per plot for the percent defoliation at 3, 7, 14, 21, and 28 Days After Treatment (DAT). Variables were subjected to ANOVA and means compared using Fisher’s PLSD at the 5% significance level.
At 3 DAT, there were no significant differences among treatments; probably due to the generally low grasshopper populations. Most of the insecticide treatments had significantly lower percent defoliation than the untreated check at 7 and 14 DAT; except for Furadan at 7 and 14 DAT, and Dimilin (1 and 2 fl oz/acre) at 7 DAT and Dimilin (1 fl oz/a) 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. As a result, none of the insecticide treatments were significantly different from the untreated check at 21 and 28 DAT indicating reduced control and residual. Results indicate that most of the insecticides tested were able to reduce grasshopper numbers and protect sunflowers up to14 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 Sunflower,
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Last Updated:
Tuesday, July 05, 2005 10:26:36 AM
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