Dissipation Rates and Effectiveness of Malathion, Imidacloprid, And Dimethoate at Controlling Asian Citrus Psyllids under Field Conditions

Citrus greening disease (Huanglongbing (HLB)) is an incurable citrus disease found globally that researchers and growers are striving to address with improved disease management strategies. In this field study, citrus trees were sprayed with three insecticides (i.e., malathion, imidacloprid, and dimethoate) at a large grove in Florida. Insecticide degradation kinetics in leaves were measured and efficacy was investigated by quantifying the target pest, Asian citrus psyllids (ACP), over time. Our findings show rapid degradation of insecticides and live ACP present after treatments in the field. Dissipation half-lives were 3.1 h (malathion), 0.6 and 2.3 h (imidacloprid), and 1.0 and 4.0 h (dimethoate). Metabolite concentrations were small but increased within 6 h after treatment. ACP populations decreased by 100% (malathion), 63-80% (imidacloprid), and 80-86% (dimethoate). The rapid insecticide degradation and efficacies less than 100% allow remaining ACP or ACP from surrounding groves to continue spreading HLB, revealing ineffective pest management.