Expanded Use of Hail Netting in Minnesota Apple: Impacts on Insect Pests, Fruit Production, and Natural Enemies

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Expanded Use of Hail Netting in Minnesota Apple: Impacts on Insect Pests, Fruit Production, and Natural Enemies

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The management of apple insect pests in orchards in the United States has historically depended upon broad-spectrum insecticides. Exclusion netting has begun to be adopted by fruit growers across the world to assist with the management of insect pests and to reduce chemical input. In apple, the first exclusion netting system was developed in the early 2000s, and new developments in color, mesh size, and material continue to be made. Hail netting, originally developed to protect pome fruit from hail damage, has begun to be adopted by growers in Minnesota, USA. The potential for hail netting to be used as a dual-purpose management tool, both to protect from hail and exclude key insect pests in Minnesota, is investigated in this study. This research examined the efficacy of hail netting as a pest exclusion tactic and the non-target effects of hail netting on fruit production and the natural enemy community. First, the efficacy of hail netting in reducing pest populations was compared to a commercial grower’s spray schedule in Minnesota. The insecticides used by the grower in 2021 and 2022 were clothianidin, abamectin, novaluron, and acetamiprid. The three insect pests that we monitored for were the codling moth (Cydia pomonella Linnaeus; Lepidoptera: Tortricidae), the apple maggot (Rhagoletis pomonella Walsh; Diptera: Tephritidae), and the red-banded leafroller (Argyrotaenia velutinana Walker; Lepidoptera: Tortricidae). This work was conducted as a two-year field study, with both years showing a significant reduction in pest pressure under the netting. Insecticide application did not significantly reduce pest pressure from any of the three pests. The interaction of netting and insecticide application was found to significantly improve fruit quality at harvest time. Neither netting nor insecticide was found to significantly influence apple yield. Second, hail netting significantly reduced predator family richness and the number of individuals that were caught. The most abundant predator family observed was Anthocoridae, along with Coccinellidae, Formicidae, and Empididae. All of these families were significantly reduced in number inside the netting. The diversity of predator families, evaluated using Simpson’s and Shannon’s diversity indices, was not significantly influenced by the netting or spray treatments. Spray treatments did not significantly reduce the family richness or the number of individual predators caught in any family. The environmental risk of the insecticides used in this study was evaluated using the Environmental Impact Quotient and the Pesticide Risk Tool. The tools had slightly different findings, but overall there was a higher risk to non-target arthropods caused by the neonicotinoids clothianidin and acetamiprid.


University of Minnesota M.S. thesis. August 2023. Major: Entomology. Advisor: William Hutchison. 1 computer file (PDF); xi, 92 pages.

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Nelson, Sally. (2023). Expanded Use of Hail Netting in Minnesota Apple: Impacts on Insect Pests, Fruit Production, and Natural Enemies. Retrieved from the University Digital Conservancy, https://hdl.handle.net/11299/259576.

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