Trunk and soil applications of imidacloprid, thiamethoxam and acibenzolar-S-methyl for SAR control of citrus canker on young fruiting citrus trees
J. H. GRAHAM (1), M. E. Myers (1). (1) University of Florida, Citrus Research and Education Center, Lake Alfred, FL, U.S.A.
Soil applications of neo-nicotinoid insecticides provide extended systemic acquired resistance (SAR) control of citrus canker caused by <i>Xanthomonas citri</i> subsp. <i>citri</i> on non-bearing citrus trees. Currently, use of neo-nicotinoids insecticides for control of the Asian citrus psyllid (<i>Diaphorina citri</i>) vector of Huanglongbing disease and leafminer (<i>Phyllocnistis citrella</i>) is limited to trees less than 2.75 m tall in part due to the potential risk for leaching of soil applied materials into the groundwater at the higher rates required for pest control on larger size trees. An alternative approach is spray application of the chemicals on the trunk. Four soil drench or trunk applications of the neonicotinoids imidacloprid (IMID; Admire Pro, Bayer) and thiamethoxam (THIA; Platinum, Syngenta) and the commercial SAR inducer acibenzolar-S-methyl (ASM, Actigard, Syngenta) were compared to untreated controls and 9 or 10 standard 21-day interval copper sprays for protection of foliage and fruit on 5 to 6-yr old ‘Ray Ruby’ grapefruit trees in an orchard in Ft. Pierce, Florida. Soil drench and trunk applications similarly reduced the incidence of canker lesions on foliage and fruit but were less effective than copper sprays. SAR inducers appeared to protect fruit by reducing incidence of foliar disease, and thereby, when integrated with 21-day interval copper sprays may improve control canker on young, fruiting trees.
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