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United States Department of Agriculture

Agricultural Research Service


Location: Citrus and Other Subtropical Products Research

2012 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 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 continues to be a problem for fresh market citrus. Studies from the 2009-2010 citrus season show that preharvest carnauba sprays significantly reduce the incidence of citrus canker on the fruits and leaves of commercial fresh citrus (e.g. grapefruit). By using the carnauba spray preharvest, the inoculum in the field is reduced and the incidence of unblemished fruit increases. In the citrus season of 2010-2011, assessments of canker infection on trees sprayed consecutively for 2 years were made in the field and in the laboratory. Application of the wax the second year showed an increase of unblemished fruit when compared with the first spray season, showing a reduction in inoculum. The sprays have been successful for two activities: the wax prevents erosion of the active compound (e.g. copper hydroxide) as well as hydrating the components in the wax, both activating them and making them available to the organism. We are now directing our efforts to lowering costs of the spray for growers by testing other waxes in the formulation. We are also incorporating different compounds in the wax(s) along with the copper that might also inhibit the Asian citrus psyllid from infecting the trees. This study is ongoing.

4. Accomplishments

Last Modified: 10/18/2017
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