SUSCEPTIBILITY AND BEHAVIORAL-RESPONSE OF RED IMPORTED FIRE ANT (HYMENOPTERA, FORMICIDAE) TO SELECTED ENTOMOGENOUS NEMATODES (RHABDITIDA, STEINERNEMATIDAE AND HETERORHABDITIDAE)

Pathogenicity of infective juveniles of selected Steinernema spp. and Heterorhabditis spp. toward developing and reproductive stages of the red imported fire ant, Solenopsis invicta Buren, was tested under labo ratory conditions. At 10(3)-10(5) infective juveniles per Petri dish, mortality of reproductive larvae, pupae, and alates ranged from 28 to 100% at higher doses after 96 h at 23-25-degrees-C. Steinernema carpoc apsae All was the most consistent species tested; this nematode caused mortality of fire ant larvae, pupae, and alates of 82-94, 64-96, and 38-99%, respectively. Although not susceptible to nematode infection, worker ants vigorously preened nematodes from brood, alates, and thems elves. In a field study, S. carpocapsae (5 x 10(6) and 2 x 10(6) drenc h, 2 x 10(6) infective juvenile injection) was applied to active fire ant mounds in 3.8-liter suspensions. Hydramethylnon (75 ml), a water d rench, a water injection, and untreated fire ant mounds were marked an d treated. Overall activity in mounds treated with nematodes of hydram ethylnon ranged from 40 to 48%. Satellite mound activity accounted for 32-44% of overall activity in mounds treated with nematodes 2 wk afte r treatment. However, 6 wk after treatment, activity in mounds treated with hydramethylnon was 44%; activity of mounds treated with nematode s ranged from 52 to 80%. Satellite mound activity accounted for 0-24% of overall activity. Whereas a soil drench of S. carpocapsae showed po tential as a control method for the red imported fire ant, colony relo cation after nematode treatment could limit overall efficacy unless ap plication techniques are developed to overcome or take advantage of th e movement.