RESOLVING INOCULUM SOURCES AND EVALUATING ALTERNATIVES TO MITIGATE POSTHARVEST DISEASES, FOOD LOSSES, AND MYCOTOXIN CONTAMINATION IN APPLE

Apples are one of the topmost consumed fruit in the United States, second in popularity only to bananas. They have an annual farm-gate value of nearly US$4 billion, with downstream revenues exceeding US$15 billion. Apples are available and enjoyed year-round because they can be held in cold storage under controlled atmosphere conditions, which suspends the ripening process such that an apple maintains its crispness and taste 9-11 months after they were harvested. Postharvest rot during storage caused by fungal pathogens is a persistent threat to the global US apple industry. This not only reduces their quality, increases food loss, but also can lead to mycotoxin contamination of processed fruit products. Annual losses due to postharvest rots range between 1%-15% in the United States, alone. Current estimates of the economic losses due to postharvest apple rots are not available; however, estimating 15% loss of the 4.5-5 million tonnes of apples produced annually in the United States, and an average price of US$1.5 per pound, up to US$2.5 billion are lost each year due to postharvest rots. Approximately a dozen diseases can affect apples during storage. The most frequent postharvest rots of apples are blue mold, caused by Penicillium expansum and other Penicillium spp., and gray mold, caused by Botrytis cinerea. The fungi causing blue mold are of most concern since several of the species produce the mycotoxin patulin. Unfortunately, no apple varieties exist that are resistant to these diseases and management options of postharvest apple rot are limited. Growers rely on continued use of synthetic fungicides, which there are few and have caused the emergence of fungicide resistant strains in apple packinghouses in the United States. This reduces their utility as control options in storage since fungicide failure is more likely to occur. Considering consumers demand apples with less pesticide residues and commercial apple cultivars lack resistance to most of the postharvest pathogens new integrated management options are necessary.Postharvest apple disease research has been limited to Washington and Oregon, demonstrating storage bins, dump tank water, and the air of the packinghouse facilities and cold rooms harbor high levels of rot pathogens that contribute to postharvest decay, with Penicillium spp. as the predominant fungus. To eradicate pathogens, treating bin surfaces with steam, cleaning packinghouse walls and floors with disinfectants, and maintaining proper chlorine levels in sizing flumes have been recommended. It is unknown if the Western U.S. research and management recommendations can be extrapolated to meet the needs for Mid-Atlantic apple growers and packers, who produce approximately 760 million pounds of apples annually. Consequently, these practices are not routinely implemented in apple packinghouses located in the Mid-Atlantic region due to the economic cost and the lack of region-specific research demonstrating their efficacy on reducing the incidence and severity of postharvest rots. There is an expressed need for research and optimized postharvest disease management recommendations, including identifying alternatives to synthetic postharvest fungicides, geared towards Mid-Atlantic apple growers and packers. This project aims to fill a major gap in knowledge for postharvest apple diseases and appropriate management strategies for the Mid-Atlantic. We will accomplish this by identifyng the fungi causing postharvest apple rots in Pennsylvania and Maryland packinghouses and determine the source of where the fungal spores originate. In addition, we will concurrently be evaluating the status of fungicide resistance among the fungal pathogens collected against the four postharvest fungicides used. Studies will investigate if wooden and plastic bins serve as a viable pathogen source for rots, as described in Western apple packhouses. Current methods, such as steam, and new tools and delivery systems, such as fogging, and organic controls will be evaluated for sanitizing bins and/or other surfaces, as well as used to limit postharvest apple decay. Science-based information will be communicated to stakeholders through extension programming both in English and Spanish for optimized chemical and cultural postharvest disease management protocols. Results from this project are expected to be transformative and impactful to many apple producing areas having similar production practices such as New England, New York, Michigan, the Midwest, and Southeast regions. Through the methods described, the ultimate goals of the project are understanding the status of postharvest apple diseases and developing tailored, cost-effective, sustainable disease management for conventional and organic Mid-Atlantic apple growers and packers. Adoption of optimized postharvest disease management strategies will be economical for the stakeholders resulting in less crop loss while reducing human health risks through limiting exposure of fruit contaminated with mycotoxins and mycotoxin-producing fungi.