Imidacloprid mobility and longevity in soil columns at a termiticidal application rate

The mobility, longevity and termiticidal activity of imidacloprid (Premise 2 termiticide; Bayer Environmental Sciences) at the termiticidal labeled rate for perimeter treatment were tested in vegetated and non-vegetated soil columns in two tests: in cone plots and in polyvinyl chloride (PVC) pipes. Imidacloprid content in the cone plot eluate peaked at 1 month, declined rapidly by the second month and then entered a lagging phase. The concentration of imidacloprid in the cone plot soil declined from 84.5 microg g(-1) initially to 7.5 microg g(-1) (non-vegetated plots) and 8.1 microg g(-1) (vegetated plots) 6 months later. Neither eluate concentration nor soil concentration was affected by the presence of vegetation in the cone plots. In the PVC pipes, the top 15 cm of which was treated with Premise 2 at the perimeter labeled rate, imidacloprid half-life was estimated at 6-9 months for vegetated and non-vegetated soil. Extractable imidacloprid declined more rapidly in the first 15 months than afterwards. Mobility of imidacloprid into lower, untreated soil depths was higher in non-vegetated pipes, and was likely due to the effect of vegetation on soil moisture. The presence of vegetation had little effect on the termiticidal activity of treated soil in the PVC pipes.