Laboratory and Field Evaluations of an Entomogenous Nematode (Nematoda: Steinernematidae) for German Cockroach (Dictyoptera: Blattellidae) Control

Abstract

Pads impregnated with the nematode Steinernema carpocapsae (Weiser) and enclosed in a moisture-retaining station were evaluated in field and laboratory experiments with the German cockroach, Blattella gennanica (L.). In continuous exposure tests without harborage, LT50s ranged from 2.06 to 12.64 d for 0.5 × 106 nematodes and 106 nematodes, respectively. LT50s estimated with Ebeling choice boxes were 2.5 to 8.4 times greater than those from the continuous exposure tests. Relative repellency, measured as the mean percentage of live cockroaches in the light side of the choice box, was greatest for stations with 0.5 × 106 nematodes (6.65%) and least (3.70%) for stations containing 2 × 106 nematodes. Movement by cockroaches confined to nematode deposits declined linearly with increasing nematode density. The number of antennal preens by confined cockroaches increased curvilinearly with nematode density. A performance index that combined choice-box repellency and mortality data indicated that stations containing 2 × 106 nematodes had the greatest potential for field effectiveness. Stations containing 2 × 106 nematodes significantly reduced German cockroach trap catch in infested apartments.