Mortality and foraging rates of Argentine ant (Hymenoptera : Formicidae)colonies exposed to potted plants treated with fipronil

摘要

Individual colonies of Argentine ants, Linepithema humile (Mayr), were collected and maintained in plastic containers and randomly selected to receive a potted oleander (Nerium oleander L.) plant with one of eight different soil treatments of fipronil, diazinon, or an untreated control. Foraging and mortality rates were observed in each colony. Reductions in the rates of ants foraging on plants were similar with all treatments; however, the mortality rates of the colonies varied among treatments. For example, 1 wk after exposure to treatments, the foraging rates on plants in all treatments except the control had dropped to zero. Soil-mix treatments of fipronil had killed >90% of worker ants at 1 wk, whereas broadcast treatments of fipronil and diazinon killed <50% of workers. The soil-mix treatments of fipronil killed all queens in 4 wk, whereas broadcast treatments of fipronil took 8 wk to kill all queens. The diazinon broadcast treatment did not kill any queens. Only fipronil soil-mix treatments prevented ants from establishing colonies in the pot. These results suggest that when studying pesticide effectiveness against Agrentine ant in the field, equivalent short-term reductions in foraging rates should not be assumed to indicate equivalent mortality of ant colonies.