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Progress on chemical management of postharvest diseases of subtropical fruits

Jim Adaskaveg: Department of Plant Pathology and Microbiology, University of California

<div>Application of postharvest fungicides is a highly effective, targeted, and economical way to protect fruit from decay after harvest and during shipment and marketing, while fungicide residues remain within MRLs, similar to preharvest field applications. These treatments are especially beneficial for fruits that are stored for extended times or that are shipped long distances. The United States has been on the forefront in developing these treatments. For sub-tropical crops such as citrus, pomegranates, pineapples, and avocados, new fungicides have been introduced to manage major diseases. Fungicides range from conventional (propiconazole) to reduced-risk (azoxystrobin, fludioxonil) to biopesticide (natamycin) compounds, and also include pre-mixtures (fludioxonil-propiconazole, -azoxystrobin, or -cyprodinil). Azoxystrobin-fludioxonil is effective against decays caused by DMI<sup>SR</sup> and MBC<sup>SR</sup> isolates of <em>Penicillium</em> spp.; propiconazole is effective against <em>Geotrichum</em> and DMI<sup>s</sup> and MBC<sup>SR </sup><em>Penicillium</em> spp. Natamycin has activity against <em>Geotrichum</em> and <em>Penicillium</em> (DMI<sup>SR</sup> and MBC<sup>SR</sup>) decays, is exempt from tolerance in North America, and potentially is an organic treatment. Although moderately effective by itself, mixtures provide high efficacy and resistance management. Fludioxonil-propiconazole, -azoxystrobin, and -cyprodinil premixtures, as well as natamycin are effective for managing <em>Alternaria</em>,<em> Botrytis, Ceratocystis, Colletotrichum, Fusarium, Rhizopus </em>spp., and other molds.</div>

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