1a. Objectives (from AD-416):
(1) Optimize effectiveness of packinghouse treatments to minimize postharvest losses. (2) Evaluate novel methods of packinghouse sanitation. (3) Preharvest measures to minimize postharvest decay losses. (4) Evaluate UV fluorescence to remove mechanically damaged fruit to reduce decay.
1b. Approach (from AD-416):
Continue laboratory tests to develop new and promising treatments to control postharvest decay of citrus fruit that are EPA "reduced risk", listed in the USDA National Organic Program, or are FDA GRAS-listed compounds. We will examine the impact the mode of application, of heat on their effectiveness and residues, and their compatibility with other compounds such as chlorine and other fungicides.
3. Progress Report:
Progress in FY12 was made on objective 2C in the parent project. Postharvest decay annually causes significant losses of fresh citrus fruit, and control of them by fungicides has been compromised by the development of resistance by the fungal decay pathogen Penicillium digitatum. Phosphites (also fungicide termed phosphonates) are salts of phosphorous acid (H3PO3), nutritionally ineffective forms of phosphorus with an oxidation state of +5, as opposed to phosphorus compounds of oxidation state +3 that are used in fertilizers and utilized by plants. Exempt from residue tolerances for many applications, they merit evaluation because of their benign environmental aspects. When applied to citrus fruit after harvest, phosphite solutions controlled postharvest decay losses significantly in repeated tests with many varieties of citrus fruit in tests conducted at the San Joaquin Valley Agricultural Sciences Center in Parlier. The reduction in prevalence of postharvest green mold among fruit after treatments containing 2% phosphite was from 40 to 90%, and was influenced by contact time of the fruit to the solution, its pH, and temperature. A commercial formulation became available in 2010 followed by another in 2012. These results were presented to growers in a written progress report to the California Citrus Research Board and an oral presentation to the University of California-sponsored Postharvest Pest Control Seminar on April 17, 2012 in Santa Barbara, California.