Efficacy of Pt® 370 Ascend™ (Avermectin Bl) Against the Red Imported Fire Ant, Solenopsis Invicta Buren, Fall, 1990

Abstract

Efficacy of Avermectin Bl-based red imported fire ant (RIFA) bait was tested. Ten 15 m radius circular test plots (approx. 0.1 ha) containing 5-8 mounds were laid out in a single-queen RIFA-infested fallow lot. For each treated plot an adjacent plot was selected as control, being part of the same colony population. The mounds were staked and numbered for identification. A single broadcast application of 0.011% Avermectin B-l was made at the rate of 1.12 kg/ha (8.2 mg Al/plot) on 21 Sep, using a precalibrated, hand-held seed spreader. The plots were treated by walking along the circumference of circles subtended by 1.5, 4.6, 7.6, 10.6, and 13.7 m radii and applying insecticide pacing normally. The activity of ants in the five treated and untreated (control) plots (replicates) was monitored by thrusting five 20 ml Fluon®-rimmed scintillation vials into each mound and pooling the ants sampled. The samples were taken at the time of application (21 Sep) and at 10 d post-application intervals (2 Oct, 12 Oct, 22 Oct, 2 Nov, and 13 Nov). Ambient and soil temperatures during the sampling were 25.19 ° 5.97°C and 24.07 ° 5.87°C, respectively. The capture of workers was used as a parameter to deduce the decline in ant activity in the mounds as a result of insecticidal application.