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United States Department of Agriculture

Agricultural Research Service


Location: Citrus and Other Subtropical Products Research

2010 Annual Report

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 1 of this in-house project: To develop new uses for coatings to preserve quality of fresh produce. 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 are spraying a light weight carnauba wax on highly susceptible grapefruit and less sensitive tangerine trees. We are using several experimental mixes and spraying on a commercial schedule. This study will take more than one season to have enough data but preliminary trends should be visible this fall when the fruit are harvested. A reduction in the inoculum in the groves over time will decrease the amount of disease and make it more manageable to control. This should 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. This is an ongoing study. MONITORING: Progress was monitored by e-mail, phone calls and meetings.

4. Accomplishments

Last Modified: 2/23/2016
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