(2nd Place) A case study of 47-years of insecticide use in Minnesota apples: Change-point analysis of pollinator risk

Neonicotinoids have been banned in Europe due to the risks they pose to pollinators, yet they remain a common insect pest control tactic in the United States. By contrast, organophosphates, formerly popular insecticides also known for their pollinator toxicity, have been phased out or banned outright. This raises the question: in practice, how does the potential pollinator risk compare between conventional insecticides and neonicotinoid use? We analyzed a time series of annual insecticide use from 1975-2023 for a commercial apple orchard using the Pesticide Risk Tool (IPM Institute, Madison, WI) to characterize potential pollinator risk. Using change-point analysis, the Kruskal-Wallis test, and the pairwise Wilcoxon test, we examined whether significant shifts in potential pollinator risk occurred as insecticide use changed over time. The change-point analysis showed that between 1975 and 2006, there was a statistically significant decrease in pollinator risk as organophosphate use declined. However, the onset of neonicotinoid use in 2007 led to a statistically significant increase in pollinator risk. The pairwise Wilcoxon test showed a significant increase in pollinator risk when substantial neonicotinoid use began (2011-2023) compared to the period before (2006-2010), with the current average yearly risk not being significantly different from risk between 1975-1984. Despite advancements in apple IPM, this study indicates that increased neonicotinoid use may lead to a greater risk for pollinators, potentially to a similar risk level as with classic insecticide regimens.