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POSTERS: Cultural control

Evaluation of UVC for suppression of powdery mildew and other diseases of strawberry in open field production
Rodrigo Borba Onofre - University of Florida - Gulf Coast Research and Education Center. Mark Rea- Lighting Research Center, Rensselaer Polytechnic Institute, Galvin Alonzo Ortiz- University of Florida - Gulf Coast Research and Education Center, Arne Stensvand- Norwegian Institute of Bioeconomy Research, Paulo Pinto de Mello Neto- University

Open fields of cv Florida Beauty and Florida127 strawberries were exposed to ultraviolet-C (UVC) doses ranging from 68 to 169 J/m2 once or twice weekly. Applications began 1 hr after sunset and were completed within 6 hrs of sunrise using a tractor-drawn array of Osram 55W 83V G55T8/OF G13 germicidal lamps (peak irradiance 254 nm, FWHM < 5 nm), backed by polished reflectors. Lamps over each row were arranged in hemicylindrical arrays, each containing 10 lamps, yielding a total array length of 180 cm. At ground speeds of 2.3 to 5.6 kph, plants were under the lamp array for 1.2 to 2.9 s. In repeated trials, UVC at 85 to 169 J/m2 applied once per week suppressed incidence of powdery mildew (Podosphaera aphanis) on fruit as well as, or more than, the best-performing fungicide treatments. There were no deleterious effects on yield of harvestable fruit. UVC doses of 68 J/m2 reduced foliar disease severity of powdery mildew by 53% when applied once a week, and by 70% when applied twice per week. Under severe conditions, higher UV dose and shorter intervals between treatments generally, but not always, resulted in greater disease suppression. No UVC treatment provided more than 10% suppression of anthracnose fruit rot (Colletotrichum acutatum) and Botrytis fruit rot (Botrytis cinerea). The UVC technology is being adapted to a variety of tractor-drawn and robotic platforms to suppress powdery mildews and arthopod pests in diverse cropping systems.