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.