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Insecticide Efficacy against Sunflower beetles on Sunflower, 2004
Janet J. Knodel, Area Extension Specialist – Crop ProtectionLorilie Atkinson, Research Specialist North Central Research and Extension Center
Sunflower beetle: Zygogramma exclamationis (Fabricius)
Registered and experimental insecticides were evaluated for their efficacy at controlling sunflower beetle and protecting sunflowers. The research plots at the North Central Research Extension Center in Minot, ND had pretreatment counts of an average of 9.4 larvae/plant and 12.5% defoliation on R2 stage sunflower. The economic threshold level for sunflower beetle larvae is 10-15 larvae/plant or 25% defoliation. Plots were 10 ft wide by 30 ft long. A RCB experimental design with four replicates was used. Insecticides were applied at R2 sunflower stage on 29 July using a handheld CO2 boom sprayer at 40 psi, 10 gpa and fitted with XR 8001VS nozzles. Five plants were assessed per plot for the number of larvae per plant and percent defoliation at 1, 7, 14, and 21 Days After Treatment (DAT). Variables were subjected to ANOVA and means compared using Fisher’s PLSD at the 5% significance level.
At 1 DAT, all of the insecticides treatments had significantly lower numbers of larvae/plant than the untreated check, except for both rates of Dimilin. Dimilin acts as an insect growth regulator and insect populations are usually reduced 7-10 DAT. There were no significant defoliation differences among treatments at 1 DAT. At 7, 14 and 21 DAT, defoliation was significantly reduced in all insecticide treatments compared to the untreated check. However, differences between insecticide treatments were not significantly different from each other. Differences between insecticide treatments at 7 DAT were not significantly different from each other in their ability to control sunflower beetle larvae, and all treatments were significantly better than the untreated check. At 14 DAT, all insecticide treatments significantly reduced the number of larvae/plant compared to the untreated check. Dimilin applied at the 1 fl oz/a rate also had a significantly higher larval count than the remaining insecticide treatments at 14 DAT. No larval counts were conducted on 21 DAT, because sunflower beetle larvae had dropped to the soil to pupate. These results indicate that most of the insecticides tested were able to reduce sunflower beetle larval numbers and defoliation, and protect sunflowers from injury up to 21 DAT.
Means within a column followed by the same letter are not significantly different (ANOVA, Fisher’s PLSD, P<0.05). a 21 DAT – No larval counts were taken, because larvae had dropped to soil to pupate. Part II. Materials Tested for Arthropod Management Insecticide Efficacy against Sunflower beetles on Sunflower, 2004
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Last Updated:
Tuesday, July 05, 2005 10:26:36 AM
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