A study from the Rodale Institute shows that integrating ultraviolet (UV) light treatments with an OMRI-certified organic fungicide can effectively manage powdery mildew in lettuce while improving yields and preserving nutritional quality. Researchers found that combining UV-B exposure with MilStop, an organic potassium bicarbonate fungicide, significantly reduced disease severity and boosted harvestable weight by nearly 45% compared to untreated plants. The approach also enhanced amino acid compounds, showing that organic growers can control disease without sacrificing crop quality. 

Scientists grew lettuce in a controlled greenhouse environment and exposed seedlings to either UV-B or UV-C light before transplanting. Plants were then treated twice during the season with MilStop or left untreated. They measured disease severity, yield, and nutrient composition, including vitamin C, sugars, minerals, and amino acids. Their results showed that MilStop consistently suppressed powdery mildew and improved yields, while UV-B exposure increased amino acid concentrations linked to plant stress resilience and nutritional value. By contrast, UV-C treatment alone had little effect on disease or yield, highlighting the importance of selecting the right type of UV exposure. 

These findings highlight innovation within organic production. By combining physical treatments like UV-B light with organic-approved fungicides, farmers can reduce crop losses from powdery mildew (a disease that can otherwise devastate lettuce yields) while supporting crop quality and potential profitability. This research adds to the growing body evidence that organic systems are not only safer, but can also produce food with improved nutritional profiles, such as higher amino acid concentrations that contribute to both flavor and health. Organic farmers continue to demonstrate that it is possible to protect crop yields, grow nutrient-rich food, and reduce agriculture’s environmental footprint.