Factors affecting the implementation of exclusion netting to control Drosophila suzukii on primocane raspberry

Abstract

Sustainable management of invasive arthropod pests requires insecticide-alternative, integrated strategies, such as protected culture. During 2016–2017, we studied the efficacy of exclusion netting at reducing infestation damage in fall-bearing raspberries caused by an invasive vinegar fly, Drosophila suzukii Matsumura. In an effort to manage outbreak infestation, we studied the efficacy of baited attracticidal spheres in netted and open plots. We also monitored the effects of netting on fruit marketability, abiotic conditions near the fruiting zone, and pollination effects due to exclusion. The results showed that while 80 g HDPE netting sufficiently deterred D. suzukii infestation early in the season, late-season infestation was often greater in netted zones compared to insecticide-treated open plots. The introduction of baited attracticidal spheres under the netting did not consistently reduce infestation, and in some cases even increased infestation late in the season, likely due to the presence of the olfactory bait. During both test years, fruit marketability was greater in netted plots compared with open plots, and in open plots, we observed more overripe fruit and additional feeding damage caused by other herbivores. However, the incidence of crumbly berry was higher in netted plots, indicating pollination deficits. Supplemental pollination appeared to reduce these effects. Although temperature did not differ significantly between netted and open plots, we also observed greater incidence of botrytis infection in netted plots containing attracticidal spheres, which was not present in netted plots alone. These data suggest that while exclusion netting may be a valuable tool for D. suzukii pest management, unless outbreak infestation under the netting and supplementation pollination are addressed, significant challenges may impede large scale implementation.