Influence of cultural conditions on the virulence of conidia and blastospores of Beauveria bassiana to the green leafhopper, Nephotettix virescens

Determinations were made of the median lethal concentration (LC 50 ) and median lethal time (LT 50 ) of conidia and blastospores of B. bassiana against adult Nephotettix virescens (green leafhoppers). There was no significant difference between the LC 50 values for blastospores produced in carbon- and nitrogen-limited cultures, but both types of blastospores were significantly less virulent than conidia. The LT 50 values of conidia and of blastospores from nitrogen-limited cultures were significantly lower than the value for blastospores produced in carbon-limited culture. The LT 50 values of conidia and blastospores increased during storage at 25 °C and were inversely related to spore viability. At all but one concentration tested, nitrogen-limited blastospores ‘adhered’ to insects more strongly than did carbon-limited blastospores. Fewer spores germinated on insect wings than on agar medium and of the three spore types studied, maximal germination on insect wings was observed with nitrogen-limited blastospores.