Post Harvest

New materials (synthetic, natural and biological) are being continuously evaluated for their potential use in managing postharvest decays of citrus. Our current focus is on new fungicides that are ‘reduced-risk’ compounds. These materials are being evaluated, developed, and registered for postharvest use against blue and green mold caused by Penicillium spp. and sour rot caused by G. citri-aurantii. New materials such as fludioxonil (Graduate) and pyrimethanil (Penbotec) as well as the pre-mixtures fludioxonil-azoxystrobin (Graduate A+) and imazalil-pyrimethanil (Philabuster) have been registered and major usage is expected with approval of international tolerances (MRLs). Another material, propiconazole (Mentor), is being registered through IR-4 with efficacy against sour rot and imazalil-sensitive populations of P. digitatum. A pre-mixture of fludioxonil+azoxystrobin +propiconazole (Graduate TDC) is in development. Thus, this project is developing new materials and combinations of materials, developing baseline sensitivity data for future reference points in monitoring for resistance, and optimizing fungicide usage by identifying rates and application strategies (compatibility with fruit coatings, sanitizing agents, heat and pH-altering salts such as sodium bicarbonate) that maximize performance against Penicillium decays and sour rot. Furthermore, studies on the characterization of fungicide resistance are done including types (qualitative or quantitative), levels (low, medium, or high), fitness (pathogenic, non-pathogenic, and virulence), and frequencies of resistance in populations of P. digitatum to the new fungicides. Studies on the genetic diversity of G. citri-aurantii using mating type and molecular methods are being summarized for publication. Additionally, we have identified several potential fungicides that can be registered as preharvest or postharvest treatments for postharvest decay control of Penicillium and brown rot (Phytophthora) decays. Preharvest treatments would be applied immediately before harvest and may be especially important when fruit are stored for an extended time in field bins (e.g. degreening fruit, excessive fruit harvested) before postharvest treatments can be applied.