Contact Activity of Residual Insecticides, 1991

Ants from colonies nesting in trees were trained to a feeding station at the terminus of a series of 3 cm diam wooden poles. After a 1 to 2 h training period, 1 section was replaced with an insecticide-treated pole and the ants were exposed as they continued to forage. After crossing the insecticide deposit the ants were swept into a plastic box (10 per box) and returned to the laboratory for observation. Exposures were conducted between 2100 and 0100 h (EST), and therefore subject to variations in ambient temperature. Bendiocarb (76% WP), chlorpyrifos (Dursban LO; 4EC), deltamethrin (5ME) and (3-cyffuthrin (10WP) were diluted in water and applied with a compressed air sprayer (40 psi, coarse fan) calibrated to deliver approximately 6 ml per sec; the spray wand was held 45 cm above the pole and moved linearly at approximately 1 ft per sec. A dry powder aerosol (bendiocarb DPA, 0.5%) was also tested; treatment was consistent with the compressed air sprayer. Poles were treated with either a 15- or 45-cm band of the insecticide, and tests were made on poles that had aged (in sheltered sites) for 1, 14 and 28 DAT. Each treatment combination was replicated 3X, and there was never any mortality in the controls. Percent mortality at 72 h (transformed by arcsine Vp) was analyzed by ANOVA with mean separations by LSD (P < 0.05).