Abstract
A laboratory bioassay was developed to test the toxicity, repellency and tunneling behavior of imidacloprid against Microtermes obesi (Holmgren). In this study >90% of termites died after 96 h exposure to 100 µg mL-1 of imidacloprid and after 168 h all the termites died at all the tested concentrations. When tested for persistence (exposure to soil aged one month after treatment), >90% mortality was observed in soil treated with 100 µg mL-1, 50 µg mL-1 and 25 µg mL-1 after 120 h exposure. Repellency test results proved imidacloprid to be a non-repellent insecticide at all tested concentrations (i.e., 100 µg mL-1, 50 µg mL-1, 25 µg mL-1, 12.5 µg mL-1, 6.25 µg mL-1, 3.125 µg mL-1 and 1.562 µg mL-1). When tested for F-1 (0.97) toxicity, it was also evident that it took more than 8 h to give 97% mortality. Tunneling behavior was also studied for cumulative tunnel distance, maximum tunnel height and number of tunnels. At higher concentrations, not only was there more mortality, but also less cumulative tunnel distance and a reduced number of tunnels.
