EFFECT OF SURFACTANTS AND FORMULATIONS ON DISTRIBUTION OF CYPERMETHRIN USED FOR SUBTERRANEAN TERMITE CONTROL IN SANDY SOIL

Abstract:
The distribution of cypermethrin (Demon@) affected by formulations and surfactants in a sandy loam soil was determined. Eight treatments consisted of Demon TC (25.3 % cypermethrin, emulsifiable concentrate) or Demon Wettable Powder (40.0% cypermethrin) with 0.25% A1 concentration mixed with or without a surfactant (0.1% of Atlox 8916TF, Tween 20 or G-3300). Each treatment was replicated three times. One control (untreated) treatment was also included. An experimental unit assigned to each treatment was a plywood box (1.83 X 1.83 X 0.6 cm) filled with sandy loam soil and covered with a 7.6 cm concrete slab. A 1.3 cm hole at the center of each slab was made by drilling through the slab. The 1.52 Liter of insecticide was applied under 172.5 KPa pressure through the concrete slab using a sub-slab injector equipped with a 10.2 cm single bored straight tip. Four soil cores measuring 93 cm in length and 2.54 cm in diameter were removed from each unit with cores 1,2, 3 and 4 located 2.5, 15.2, 30.4 & 45.6 cm below the bottom of the concrete slab, respectively. Each core was divided into 9 soil samples (first 5 samples, 7.6 cm in length and the remaining 4 samples 15.2 cm in length). Cypermethrin from soil samples was extracted and analyzed by gas chromatography. Data were statistically analyzed by Proc GLM:Repeated Measures Analysis. The results indicated the type of insecticide formulation did not significantly affect vertical penetration or lateral distribution. The presence of surfactants generally yielded greater lateral distribution of cypermethrin. Demon TC plus Atlox and Demon WP plus G-3300 provided the highest lateral distribution (53.2 cm) from the injection point with amounts more than the minimum of 1 pg of cypermethrin per gram of soil required for termite control. Cypermethrin applied without a surfactant yielded 30 cm of lateral distribution from injection point with amounts adequate to control subterranean termites.