Factors affecting distribution patterns of chlorpyrifos and permethrin applied as termiticides to soil

Abstract

Soil models in 190-liter containers were used to evaluate the effect of soil type (sandy, silty, and clay loams), soil moisture (25%, 50%, or 100% of field capacity), and rainfall (2.5, 5.0, or 15.0 cm) on the distribution patterns of termiticides (cworpyrifos and pennethrin). Tenniticide with 1% active ingredient was poured into a hemispheric depression on the surface of 1 10 kg of soil and subjected to simulated rainfall after application or saturation before application. Twenty-four hours after infiltration of temiiticide, a pattern of soil samples along a vertical profile was analyzed by gas chromatography for concentration (ppm) of active ingredient. Results showed that 75 to 90% of the active ingredient recovered from each treatment were adsorbed directly below the depression in the upper 10 cm of all soils. Lateral movement of termiticide was insignificant beyond the trench. Sandy soils contained more active ingredient in the upper 5 cm than clay-rich soils before a rainfall, but had greater movement than clay-rich soils due to a rainfall. At 100% soil moisture, the clay-rich soils had 10 to 30% less cworpyrifos in the upper 5 cm, but 10 to 30% more at 5 to 25 cm of depth. Soil moisture and rainfall caused statistically significant movement in each test, but enough tenniticide remained behind to maintain the dosage required for control of subterranean termites.