Two-Year Survey of Botrytis Fruit Rot Levels in Commercial Strawberry Fields in California with and without Fungicide Applications

Botrytis fruit rot (BFR) causes significant losses in-field and postharvest in strawberries and is mainly managed by fungicides. Strategically applying fungicides only during wet and cool periods would reduce fungicide resistance development and grower costs. A survey of BFR levels in field-grown strawberries with and without fungicide applications was conducted in Santa Maria, California. Weather data were collected to calculate the BFR risk factor using Florida's Strawberry Advisory System (StAS). There were no significant differences between fungicide and no-fungicide treatments for in-field and postharvest BFR incidence in 2021 and in-field BFR incidence in 2022, while the no-fungicide treatment showed higher postharvest BFR incidence in 2022. Average in-field BFR incidence for fungicide and no-fungicide treatments was 2.6% and 2.5% for 2021 and 3.0% and 3.7% for 2022. Average postharvest BFR incidence for fungicide and no-fungicide treatments was 1.8% and 2.0% for 2021 and 0.6% and 1.5% for 2022. BFR risk factor was significantly associated with BFR incidence in 2021, but not in 2022. StAS predicted a 50% and 44% fungicide application reduction in 2021 and 2022 compared to grower standard treatments. These results indicate the potential of reducing fungicide use without compromising BFR control in California strawberry production.