The California Department of Food and Agriculture’s (CDFA) Office of Pesticide Consultation and Analysis (OPCA) and the University of California, Davis recently released a report, “Impacts on Pest Management Costs of Resistant Diamondback Moth Outbreaks in Central Coast Brassicas.”

The CDFA-OPCA report described substantial county- and crop-level variation in changes in pest management costs between 2023 and 2024. Further, broccoli and cauliflower in Monterey County and Brussels sprout in Ventura County experienced the largest percentage increases in insecticide use, leading to dramatic per-acre management costs (+61.8%, +54.7%, and +70.6% respectively) and total management costs (+75.8%, +87.8%, and +70.6% respectively) during this time, consistent with the reported severe pest pressure and reduced control efficacy in 2024. Western Growers is working with this office to develop a position paper that describes the findings and further highlights the challenge.

The diamondback moth (DBM), Plutella xylostella is the most economically damaging pest of brassica crops in California. Management of DBM is challenging because of its demonstrated ability to rapidly develop resistance to a wide range of insecticides. Recent monitoring has documented extensive resistance among DBM populations in the California Central Coast region, leading to increased control failures and outbreak conditions over time. Reports from industry members indicate that 2024 and 2025 have been particularly problematic for brassica producers in the region.

Growers have been increasingly challenged by this high priority pest, reporting increased yield loss, rejected shipments, and reduced efficacy of existing pest control tools.

Read the full report “Impacts on Pest Management Costs of Resistant Diamondback Moth Outbreaks in Central Coast Brassicas.”