Susceptibility and behavioral response of red imported fire ant (Hymenoptera: Formicidae) to selected entomogenous nematodes (Rhabditida: Steinernematidae & 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 laboratory 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 carpocapsae 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 themselves. In a field study, S. carpocapsae (5 x 10(6) and 2 x 10(6) drench, 2 x 10(6) infective juvenile infection) was applied to active fire ant mounds in 3.8-liter suspensions. Hydramethylnon (75 ml), a water drench, a water injection, and untreated fire ant mounds were marked and treated. Overall activity in mounds treated with nematodes of hydramethylnon ranged from 40 to 48%. Satellite mound activity accounted for 32-44% of overall activity in mounds treated with nematodes 2 wk after treatment. However, 6 wk after treatment, activity in mounds treated with hydramethylnon was 44%; activity of mounds treated with nematodes ranged from 52 to 80%. Satellite mound activity accounted for 0-24% of overall activity. Whereas a soil drench of S. carpocapsae showed potential as a control method for the red imported fire ant, colony relocation after nematode treatment could limit overall efficacy unless application techniques are developed to overcome or take advantage of the movement.