Integration of soil applied neonicotinoid insecticides and acibenzolar-S-methyl for systemic acquired resistance (SAR) control of citrus canker on young citrus trees

- Neonicotinoids produce season-long systemic acquired resistance (SAR) control of citrus canker.
- Soil drenches of acibenzolar-S-methyl (ASM) rotated with neonicotinoids were effective for suppressing citrus canker.
- SAR treatments were comparable to sprays of copper or streptomycin contact bactericides.
- SAR induced by neonicotinoids for control of citrus canker may be augmented with ASM.

Soil application of systemic neonicotinoid insecticides for control of psyllid vectors of Huanglongbing disease on young citrus trees also produces season-long SAR control of citrus canker caused by Xanthomonas citri subsp. citri Schaad et al. The neonicotinoids imidacloprid (IMID) and thiamethoxam (THIA) were compared with soil or sprinkler applications of the commercial SAR inducer acibenzolar-S-methyl (ASM) and foliar sprays of copper hydroxide (CH) and/or streptomycin (STREP) to evaluate their effects on the percentage of canker-infected leaves on 2-yr-old 'Vernia' orange and 3-yr-old 'Ray Ruby' grapefruit trees in Southeast Florida. All treatments significantly reduced the incidence of foliar canker compared to the untreated check. Soil drenches of ASM and season long rotations with IMID and THIA were highly effective for suppressing foliar canker on young grapefruit and orange trees under weather conditions absent of high intensity rains or tropical storms. Sprinkler application of ASM was less effective than soil drench. The level of control for SAR treatments was comparable to eleven 21-day interval sprays of CH and/or STREP. SAR induced by soil-applied insecticides provides substantial benefits for canker disease management on young citrus trees that may be augmented with ASM.