Continuing the Search for an Effective Preharvest Fungicide with Residual Posthavest Decay Control for Florida Fresh Citrus

Abstract

Three studies were conducted in 2010 on ‘Sunburst’ tangerine and ‘Marsh’ or ‘Ruby Red’ grapefruit to evaluate the effectiveness of applying fungicides before harvest, on reducing postharvest fruit decay. Commercially mature fruit were harvested twice, between 1 and 8 days after administering the field treatments, degreened for 2 days with 5 ppm ethylene at 85 °F (29 °C) and 90% relative humidity, and then stored at near ambient conditions around 77 °F (25 °C). Relative humidity was maintained between 80% and 90% during storage. As in previous years, preharvest application of benomyl (Benlate) or thiophanate-methyl (Topsin) resulted in the best decay control, usually resulting in at least 66% less decay after storage compared to the control (water-dipped) fruit. Unfortunately, these two materials are no longer labeled for citrus. Results with materials containing fludioxonil (Switch and Scholar) were mixed, with significantly less postharvest decay developing in some tests, and no effect in others. Even though materials containing fludioxonil occasionally reduced postharvest decay, they do not appear to be consistent replacements for benomyl or thiophanate-methyl.