D3420: 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, the presence or absence of Brassicaceae species and other habitat information was recorded for one year. We built a variety of models to investigate the effect of temperature and habitat on P. xylostella counts in three different agricultural microclimatic areas in the county. We are evaluating the predictive value of models using daily temperature data from PRISM for each sampling site and hourly data from one local weather station. Preliminary results show that the average daily temperature seven days before counts using PRISM data provided the best model fit for explaining counts. Daily average number of hours above 10 degrees Celsius in the previous fourteen days also provide similar AIC values even when only one measurement was available for the county at each time point. Growing area and vegetation type were not significant. The presence or absence of brassicas was not a good predictor of P. xylostella 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.