Tunneling Response and Mortality of the Western Subterranean Termite (Isoptera: Rhinotermitidae) to Soil Treated with Termiticides

Western subterranean termites, Reticulitermes Hesperus Banks, did not tunnel in soil with particle sizes ranging from 0.84 to 2.36 mm. Instead, they tunneled at equal rates in soils with particle sizes ranging from < 0.84 to > 0.15 mm. The latter range of soils was treated with termiticides in the study. In continuous-exposure studies in which termites were placed on soil treated at ≥ 50 ppm with termiticide, bifenthrin, cypermethrin, or permethrin had the greatest activity. Soil treated with chlordane, permethrin (< 50 ppm), or chlorpyrifos formulations acted somewhat more slowly than bifenthrin, cypermethrin or > 50 ppm permethrin. Fenvalerate (< 100 ppm) and isofenphos formulations were the least active treatments. In tunneling studies, termites did not tunnel into soil treated with formulations of bifenthrin or cypermethrin, even at the lowest concentration tested. No tunneling occurred in soil treated with formulated chlordane, chlorpyrifos, fenvalerate, isofenphos, or permethrin at concentrations ≥ 50 ppm. Mortality from the tunneling activities was greatest in tubes filled with soil treated with formulated bifenthrin and chlorpyrifos. Even though termites tunneled only in the untreated soilbelow the soiltreated with chlordane, chlorpyrifos, fenvalerate, isofenphos, or permethrin formulations at concentrations ≥50 ppm, mortality and sublethal effects were observed. Insecticide probably diffused from treated areas to untreated areas in concentrations high enough to produce kill or affect behavior.