Canker Control Trials in Florida for Grapefruit and Hamlin Orange, 2008
Jim Graham Citrus
Research and Education Center University of Florida, IFAS
700 Experiment Station Road Lake Alfred, FL 33850
Control of citrus canker in Brazil and Argentina is based on an IPM approach that foremost relies on planting of resistant varieties. In Florida, the fresh fruit and processing industries are heavily based on highly susceptible grapefruit and moderately susceptible Hamlin orange, respectively, which makes it necessary to rely more on other IPM measures. In South America this includes the use of windbreaks and bactericidal copper sprays to suppress the bacterium and prevent spread to non-infested areas. Kocide 2000 at rates as low as 0.5 lb metallic copper per acre is effective for reducing fruit disease and premature drop on moderately susceptible orange varieties in Brazil. Testing of copper formulations and rates in Florida is crucial to determine the efficacy of copper programs for control of the disease on grapefruit to qualify them for movement to the packinghouse for shipment as asymptomatic fruit or to reduce premature fruit drop of early oranges to minimize yield losses. In the case of fresh grapefruit this means that canker disease levels on fruit should not exceed 5% in the grove and should be reduced by pre-selection to 1% or less when entering the final packing process. Major questions for grapefruit are 1) can this level of control on grapefruit be achieved without windbreaks, 2) how long through the season will it be necessary to spray to protect the fruit, For early oranges the questions are what rates and duration of sprays are effective to minimize the amount of copper applied per acre season to reduce costs. Higher rates and longer durations of copper sprays risk phytotoxicity to fresh fruit, induction of copper resistance in the pathogen, soil accumulation and environmental contamination by copper. The purpose of these trials on grapefruit and Hamlin orange is to complete the initial assessment of canker control for fresh grapefruit in an east coast grove and Hamlin orange in a south central grove.