California’s Mediterranean fruit fly eradication program: impact of rising temperatures on population dynamics and control efforts

Abstract

The Mediterranean fruit fly, Ceratitis capitata (Wiedemann), is a globally significant pest with a broad host range and high ecological adaptability. It infests over 250 crop types and causes significant economic losses through crop damage and trade restrictions, resulting in persistent pressure on California’s high-value agricultural economy and reinforcing the need for long-term management. In California, eradication efforts rely on the Sterile Insect Technique (SIT) and the Preventive Release Program (PRP), but rising temperatures linked to climate change threaten their long-term success. Therefore, I investigated how rising temperatures affect Medfly population dynamics, their thermal resilience, and the effectiveness of eradication strategies in California. I analyzed 37 years (1987–2024) of detection and temperature data across 13 counties, using regional averages and models stratified by biologically meaningful temperature ranges to assess how temperature influences fly activity and control outcomes. Daily Medfly trap records from the California Department of Food and Agriculture (CDFA) and daily surface temperature data from the National Oceanic and Atmospheric Administration’s (NOAA) National Centers for Environmental Information (NCEI) were aggregated to monthly values to ensure temporal consistency across datasets and support long-term trend analysis. Wild Medfly counts were highest below 24°C (75.2°F) and declined sharply above 29°C (84.2°F), indicating temperature-linked suppression. SIT success also declined in warmer conditions, especially in southern California, where sterile-to-wild fly ratios dropped below performance thresholds. Regional warming trends, confirmed through annual and five-year moving averages, further contextualize these declines. Continued detections in cooler counties such as Alameda and Santa Clara suggest localized adaptation or microclimatic buffering. My findings highlight the need for regionally tailored, climate-adjusted strategies to address ecological variability and constraints of current pest management methods.