Impact of climate change on navel orangeworm, a major pest of tree nuts in California

California's agricultural sector is the highest valued agricultural sector in the United States. It is also a global leader in the production of various specialty crops, including three major tree nuts - almond, walnut, and pistachio. These three nut crops accounted for approximately 16% of the state's total agricultural economy. Current and future changes in climate pose many challenges in agriculture and impacts related to increased pest pressure in agriculture due to elevated temperatures are significant. The navel orangeworm, Amyelois transitella (Walker), is the most challenging pest of tree nuts in California and often cause a significant economic loss despite the careful implementation of multiple pest control tactics. Temperature variations can directly affect the developmental rates, behavior, and overall population dynamics of this pest, and it is critically important to understand these dynamics with respect to climate change. The objective of this study was to quantify changes in the timing and number of navel orangeworm generations in almonds, walnuts, and pistachios for the entire Central Valley of California using projections from ten general circulation models (GCMs) under two emission scenarios. The results suggest that navel orangeworm is likely to complete its life cycle much faster under climate change due to projected temperature increases. The results also suggest that under future climate change, navel orangeworm can complete one additional generation within the growing season and likely going to pose significant risks to these major nut industries in the future. Quantifying navel orangeworm generations and assessing risks to tree nuts under climate change can help facilitate and strategize integrated pest management (IPM) practices to the sustainability of the production systems by minimizing risks.