Codling moth pest pressures and pest control efficacy under climate change

Abstract Climate change impacts on pests and pest management have important implications for food security. Existing literature has noted that pest voltinism (number of annual generations) is expected to increase with accelerated heat-unit accumulation, implying the need for increased pest control. However, accelerated heat-unit accumulation can also impact the efficacy of behavioral (pheromone-based mating disruption) and chemical pest control strategies and this aspect is unexplored. Using codling moth in the apple-growing Pacific Northwest United States as a case study, we quantified the impacts of climate change on both pest populations and pest control efficacy. Consistent with studies in other regions, we report an increase in voltinism. However, we also found new opportunities for effective pest management that can lead to reduced pesticide use and associated environmental and worker health benefits, though they come with additional costs and risks. Our simulations indicate that temperature-driven insect phenology shifts coincide with shorter photoperiod length, leading to a larger fraction of the first-generation codling moth larvae entering diapause, reducing the population size of subsequent generations within the year, though elevating the risk of increasing the next year’s spring population. We also found that behavioral control strategies become more effective under climate change. In contrast, the windows of opportunity for pesticide control shrink. However, when the first generation is effectively controlled with a combination of behavioral and pesticide control, there are opportunities for reduced pesticide use later in the season. These competing responses in both pest populations and pest control efficacy suggest a possibility that the net climate change effects on codling moth may not be severely detrimental to apple production if pest control strategies are optimized. Other complex competing effects exist, but key knowledge gaps preclude taking a holistic approach to quantifying the net climate change response, and addressing these gaps needs to be prioritized.