Uncovering the climatic and environmental factors that affect abundance and management of Plutella xylostella in Ventura County

In Ventura County, California, cole crop production is increasingly threatened by damage from the pest Plutella xylostella, which has developed high rates of insecticide resistance locally. This issue is costing growers millions of dollars in losses, but we do not understand the factors that affect P. xylostella‘s abundance and the risk of outbreaks in Ventura County. We collected weekly counts of P. xylostella male adults using pheromone traps between 2022 and 2024. Additionally, we recorded information on the presence of cole crops and wild Brassicaceae for each trap every week for one year. We are building a variety of models to investigate the effect of climatic factors and habitat features on P. xylostella‘s counts in three different agricultural microclimatic areas in the county. Preliminary results show that Month was a significant factor affecting P. xylostella‘s counts, and that growing region and dominant vegetation type (agricultural vs. natural) were not significant. This suggest that climatic factors are most important for predicting pest outbreaks in the region. To explore this further, we are currently modeling climate data from PRISM and data from local stations to evaluate which sources of climate data improve the predictive value of the models. We are also investigating the effect of habitat features using more detailed data on the presence of cole crops and wild brassicas on pest counts. Our results will increase understanding of the factors underpinning P. xylostella’s infestations and provide tools for more precise decision-making allowing growers to integrate more effective and sustainable management strategies.