Oral to xicity of Various Insecticides, 1990-1991

Abstract

Five insecticides (abamectin, chlorpyrifos, dechlorane, permethrin, and sulfluramid) were evaluated as potential bait toxicants for black carpenter ants. All testing was done after sunset, between 2100 and 0100 h, with foragers from colonies nesting in trees. Technical abamectin, dechlorane, and sulfluramid were solubilized in acetone (20 ml) to 25 mg/u,l; 50mg of Tween80 was added to enhance even mixing in the sugar-milk bait. Formulated chlorpyrifos (4 E) and permethrin (2 E) were used, since the above procedure had not been adopted when they were tested. An appropriate volume of concentrate was diluted in given weight of sugar-milk bait (10 g raw sugar in 50 ml whole milk). Fresh sugarmilk dilutions were prepared each evening and transported on ice. Ants were attracted to a feeding station at the terminus of 3-cm diam wooden poles, supported at 50 cm above the ground, originating from a tree where the colony nested. Once ants were traveling along the poles, a bait dish on the feeding station was filled with 1 ml of toxic bait. After ants fed to repletion, and were returning to the nest, they were transferred to plastic boxes (10 per box) with a ventilated lid. This was continued until approximately 30 ants (range: 28 to 31) were dosed. Returned to the laboratory (25 ° 5°C, ambient RH), the ants were provided a moistened dental wick, and observed for cumulative mortality at 6 and 12 h after treatment and then at 12 h intervals for 21 d; dental wicks were wetted daily. At varying DAT, LC^s were estimated by regression of probit mortality vs. log10 of concentration (ppm). LT30S for 500 ppm abamectin, dechlorane, and sulfluramid and 20 ppm chlorpyrifos and permethrin were estimated by regression of cumulative probit mortality vs. logio of time (d); for LTJQS, ants fed untreated bait served as controls monitoring natural mortality.