Infodoc : Sciences, Techniques et Culture

An assessment of the sub lethal effects of abamectin on queens of the leaf cutting ant acromyrmex subterraneus subterraneus (Hymenoptera : formicidae) was carried out. A concentration response bioassay was conducted by exposing media workers (head capsule width raging from 1.69 to 1.83 mm) to filter paper impregnated with abamectin residue. This bioassay allowed selection of the abamectin concentration (0, 10, 50 and 100 mg AIml -1) to be used in experimment in which eight queens were exposed to the insecticide. The highest concentration killed queens, but those exposed to lower concentrations survived and were placed back in their nests. Reductions in leaf consumption, fungus garden volume, and foraging activity were abserved in colonies whose queens were exposed to higher abamectin[...]

An assessment of the sub lethal effects of abamectin on queens of the leaf cutting ant acromyrmex subterraneus subterraneus (Hymenoptera : formicidae) was carried out. A concentration response bioassay was conducted by exposing media workers (head capsule width raging from 1.69 to 1.83 mm) to filter paper impregnated with abamectin residue. This bioassay allowed selection of the abamectin concentration (0, 10, 50 and 100 mg AIml -1) to be used in experimment in which eight queens were exposed to the insecticide. The highest concentration killed queens, but those exposed to lower concentrations survived and were placed back in their nests. Reductions in leaf consumption, fungus garden volume, and foraging activity were abserved in colonies whose queens were exposed to higher abamectin concentration (50 mg AIml -1). Colonies with queens exposed to 50 mg AIml -1 were suppressed after 11 weeks. The dissection of queen ovaries revealed a marked decrease in the
number of ovarioles per ovary and oocytes per ovariole with increased insecticide concentration. It would appear that, as abamectin exposed queens became reproductively impaired, producing little or no progeny, colony numbers were not replaced and this led to colony suppression.