QUANTIFICATION OF INVASION OF 2 STRAINS OF STEINERNEMA-CARPOCAPSAE (WEISER) INTO 3 LEPIDOPTERAN LARVAE

Studies with last instar larvae of the fall armyworm, Spodoptera frugi perda U. E. Smith), the black cutworm, Agrotis ipsilon (Hufnagel), and the greater wax moth, Galleria mellonella (L.) were used to quantify the invasive ability of two strains (All and Mexican) of Steinernema c arpocapsae and to determine how factors in the bioassay procedure affe ct both nematode invasion and host mortality. Nematode invasive abilit y was variable, with 10-50% of nematodes successfully infecting the ho st. The percentage of infectives invading the host (invasion efficienc y) was positively related to increases in length of host exposure time and number of hosts per arena, negatively related to increases in sub strate surface area per host, and not affected by nematode concentrati on. There was a direct relationship between concentration applied and the number of nematodes invading the host. Mortality was less affected than invasion efficiency by bioassay conditions and appears to be a m uch less sensitive index of nematode activity than invasive ability.