1a. Objectives (from AD-416)
Study the effects of new technologies applied pre-harvest to protect fruit from disease and postharvest decay, including studies with citrus canker and other emerging diseases, on tropical and subtropical fruit.
1b. Approach (from AD-416)
Initially we will test these natural compounds in the laboratory on fruit pieces in specially constructed containers. These compounds will be new for these applications in Florida. We will check for phytotoxicity, efficiency of combating disease under laboratory conditions and ease of use. This work will be conducted in the microbiology labs at the Citrus and Subtropical Products Research Laboratory, Winter Haven, Florida. Information from this preliminary work will be used to study these compounds pre-harvest on fruits in the field in collaboration with grower cooperators. From these field tests, we will be able to see the efficacy of using these natural coatings pre-harvest to keep fruit disease free and ready for packing, shipping and sale. For work with citrus canker we will determine if these compounds reduce inoculum and instance of canker, and open markets for shipment.
3. Progress Report
This project is related to Objective 3 of this in-house project: Develop pre- and postharvest treatment protocols for reducing specific decay pathogens using sanitizers, antimicrobials, such as plant (including citrus) essential oils, with or without coatings and/or other surface treatments and storage atmospheres to minimize postharvest losses and maximize shelf life. Citrus canker is a bacterial disease of all citrus and its occurrence in Florida has put the fresh market industry under strict quarantine. The bacterial inoculum is spread by wind and rain. In Florida, this means that the inoculum is most dense when the fruit and leaves are most susceptible. In this study we sprayed a light weight carnauba wax on highly susceptible grapefruit and less sensitive tangerine trees. We used several experimental mixes and sprayed on a commercial schedule. This study is ongoing incorporating several commercial groves from central and south Florida. Data is collected in the field and in the packinghouse using disease assessment keys. A reduction in the inoculum in the groves over time will decrease the amount of disease and make it more manageable to control. This will result in lifting of some of the fresh fruit restrictions for shipping. Preliminary data show that preharvest carnauba wax sprays combined with pesticides can significantly reduce citrus canker in the field and has an even greater effect on the reduction of melanose. With the advent of blackspot threatening Florida citrus, this technology has applications for several diseases threatening the State, and has resulted in a patent application. Progress was monitored by e-mail, phone calls and meetings.