Persistence and Efficacy of Termiticides Used in Preconstruction Treatments to Soil in Mississippi
2006
Mulrooney, J.E. | Davis, M.K. | Wagner, T.L. | Ingram, R.L.
Laboratory and field studies were conducted to determine the persistence and efficacy of termiticides used as preconstruction treatments against subterranean termites. Bifenthrin (0.067%), chlorpyrifos (0.75%), and imidacloprid (0.05%) ([AI]; wt:wt) were applied to soil beneath a monolithic concrete slab at their minimum labeled rates. Soil samples were taken from three depths (0-2.5, 2.6-7.6, and 7.7-15.2 cm) at six sampling times (0, 3, 6, 9, 12 and 48 mo) from sites in Harrison and Oktibbeha counties in Mississippi. Residue analyses were conducted on the 0-2.5- and 2.6-7.5-cm depths, and bioassays were conducted using all three depths. In field studies, significant termiticide degradation occurred between sampling times 0 and 48 mo for all termiticides. At all sampling times, the top 2.5 cm of soil contained more termiticide than the other depths. Time to 50% dissipation of termiticide in the 0-2.5-cm depth was 9, 6, and 2 mo for bifenthrin, chlorpyrifos, and imidacloprid, respectively. Termite mortalities in contact bioassays remained high for bifenthrin and chlorpyrifos throughout the 48-mo sampling period; however, mortality of termites exposed to imidacloprid-treated soil dropped after the initial sampling. Termites readily penetrated all termiticide-treated soil in bioassays of 52-mm soil cores at 48 mo. Percentage of mortality in these bioassays was 15, 43, and 13 for bifenthrin, chlorpyrifos, and imidacloprid respectively.
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