LABORATORY AND FIELD EVALUATIONS OF AN ENTOMOGENOUS NEMATODE (NEMATODA, STEINERNEMATIDAE) FOR GERMAN-COCKROACH (DICTYOPTERA, BLATTELLIDAE) CONTROL

Pads impregnated with the nematode Steinernema carpocapsae (Weiser) an d enclosed in a moisture-retaining station were evaluated in field and laboratory experiments with the German cockroach, Blattella germanica (L.). In continuous exposure tests without harborage, LT50s ranged fr om 2.06 to 12.64 d for 0.5 x 10(6) nematodes and 10(6) nematodes, resp ectively. LT50s estimated with Ebeling choice boxes were 2.5 to 8.4 ti mes greater than those from the continuous exposure tests. Relative re pellency, measured as the mean percentage of live cockroaches in the l ight side of the choice box, was greatest for stations with 0.5 x 10(6 ) nematodes (6.65%) and least (3.70%) for stations containing 2 x 10(6 ) nematodes. Movement by cockroaches confined to nematode deposits dec lined linearly with increasing nematode density. The number of antenna l preens by confined cock-roaches increased curvilinearly with nematod e density. A performance index that combined choice-box repellency and mortality data indicated that stations containing 2 x 10(6) nematodes had the greatest potential for field effectiveness. Stations containi ng 2 x 10(6) nematodes significantly reduced German cockroach trap cat ch in infested apartments.