Uptake, translocation, persistence and fate of azadirachtin in aspen plants ( Populus tremuloides Michx.) and its effect on pestiferous two-spotted spider mite ( Tetranychus urticae Koch)

Abstract

A commercial neem formulation containing azadirachtin-A (AZ-A) was applied to the soil around the root system of potted aspen ( Populus tremuloides Michx.) plants. The uptake, translocation, persistence and dissipation of the chemical in the plants were studied. The effect of foliar residues of AZ-A on two-spotted spider mite ( Tetranychus urticae Koch) populations was also evaluated. The compound was taken up by the root system within 3 h and translocated in the stem and foliage within 3 days, confirming that AZ-A is systemic. The peak concentrations (μg/g, fresh weight) of AZ-A occurred at 10 days post-treatment, and were distributed in roots, stem and foliage in the ratio of 8.1:1.0:2.3, respectively. The rate of dissipation of AZ-A from the matrices was moderately rapid, and the residual concentrations on the last day of sampling (50 days post-treatment) in roots, stem and foliage were in the ratio 2.7:1.0:1.2, respectively. Control of mites by AZ-A residues in foliage was statistically significant, and the bioactivity declined within 30 days. The final residue of AZ-A in the soil after 50 days was about 25% of the initial value, with a half-life of dissipation of about 26 days.