Design, Construction, and Evaluation of Equipment for Nighttime Applications of UV-C for Management of Strawberry Powdery Mildew in Florida and California

We designed and constructed two tractor-drawn ultraviolet-C (UV-C) lamp arrays housed in hemicylindrical hulls adapted to two widths of raised bed planting systems for strawberry. Onboard UV dosimeters were fitted to the arrays to monitor UV-C output in field studies to suppress strawberry powdery mildew. Nighttime applications of UV-C were evaluated in replicated-plot field plantings in Florida and in California. Suppression of powdery mildew by nighttime applications of UV-C at 200 J m −2 was equivalent to that provided by weekly fungicide applications in California and superior to that provided by fungicide treatments in Florida. Costs of construction and operation of the UV-C apparatus were estimated to allow comparisons to conventional fungicide-based suppression of disease. UV-C applications had no negative effects on yield nor any visual phytotoxic effect on plants or fruit throughout the season. The results confirm and expand upon previously published studies involving UV-C applications in different environments.