|Leite, Rui P. Jr.|
Submitted to: Proceedings of Florida State Horticultural Society
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/7/2006
Publication Date: N/A
Citation: Interpretive Summary: Field trials have taken place for a number of years to search for new chemical compounds to better control citrus canker. Chemical compounds were prescreened for activity against citrus canker by the Florida Department of Agriculture and Consumer Services, Division of Plant Industry. Those showing promise were tested in limited quarantine field trials using potted citrus trees in a cooperative project with the University of Florida. Any promising compounds passing both screenings, were taken to Brazil and tested in full field trials in commercial citrus. In all cases the new compounds were tested against copper hydroxide, which has been the superior chemical control compound for many years. None of the new compounds tested exceeded copper hydroxide in effectiveness of controlling canker, however a few have show to be nearly equivalent in control of the disease. To date, the traditional copper containing compounds remain equal to or superior to all novel compounds that have been tested.
Technical Abstract: Field trials conducted in Brazil demonstrate that copper formulations (copper hydroxide, CH; copper oxychloride, COC) even at reduced rates are consistently effective for control of canker on moderately susceptible orange varieties. Contact activity to replace and/or reduce copper could minimize potential risks of bacterial resistance, soil accumulation, and environmental contamination. Alternative protectant materials, including the fungicide famoxate (Dupont Crop Protection) and the antibiotic gentamicin (GWN 9350, Gowan Co.), are under field evaluation. At a south Florida canker quarantine facility, trials showed that gentamicin (GWN 9350) formulated for greater rain fastness was effective for reducing disease on susceptible Pineapple sweet orange and Swingle citrumelo seedlings over a 3 year period. In Brazil, on mid-season Pera sweet orange, six applications of CH and COC at 0.5x of the label rate were effective for reducing canker on foliage, defoliation, and fruit infection. Control was reduced at lower rates of CH (0.5x, 0.25x, 0.125x), but combination of the fungicide famoxate with the reduced rates of CH did not show greater control activity than the lower rates of CH alone.