Organic Control of Spotted Wing Drosophila in Jersey Blueberry, 2020

This trial was conducted to evaluate the efficacy of spray programs, including the insecticide Grandevo at various rates and formulations against spotted wing drosophila (SWD) in blueberry. Six-bush plots were established in a mature ‘Jersey’ blueberry planting (row spacing 12′ × 4′) located at the Trevor Nichols Research Center in Fennville, MI. Treatment plots were replicated four times and set up in an RCB design. Applications began 29 Jul at first SWD trap catch with ripe fruit and were repeated weekly for 3 to 5 wk. Test materials were applied with an FMC 1029 airblast sprayer calibrated to deliver 50 GPA at 2.5 mph. No foliar maintenance pesticides were applied to the test plots during the trial.

Fruits were hand-harvested on 3, 10, and 17 Aug. One pound sample of blueberries were collected from each plot and weighed using an analog scale. Plots containing less than one pound of fruit at sample date received a calculated value of SWD per pound. The fruit samples were evaluated using the Washington State Department of Agriculture brown sugar method as follows. Blueberries were crushed in a sugar solution containing 7 pounds of brown sugar to 5 gallons of water. The SWD larvae were allowed to float and were subsequently counted. Data of the number of larvae per pound were analyzed using ANOVA with means separation by Tukey’s HSD at P = 0.05 after log transformation of 3 Aug data and square root transformation of 10 and 17 Aug data.

Grandevo + Nufilm (1 qt and 3 qt treatments) and the Grandevo + Nufilm + JetAg treatment significantly reduced the incidence of SWD infestation in blueberry fruit compared to the untreated check on 10 and 17 Aug (Table 1). The 17 Aug evaluation showed the highest levels of SWD infestation, and all treatments significantly reduced infestation compared to the untreated check. Means comparisons between treatment programs including 1, 2, or 3 qt rates of Grandevo were not significantly different on any evaluation date.¹

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