Susceptibility of larvae of Trichoplusia ni and Anticarsia gemmatalis to intrahemocoelic injections of conidia and blastospores of Nomuraea rileyi

The LD₅₀ for larvae of Trichoplusia ni injected with blastospores of Nomuraea rileyi was 4.30 ± 1.16 hyphal bodies/larva; the LD₅₀ for injected conidia was ca. 25,000 conidia/larva. The dose-mortality regression line for blastospores was Y = 4.6504 + 0.5487 X. Larval mortalities of Anticarsia gemmatalis and T. ni at 100 blastospores/larva were 0.4 ± 0.5% and 96.7 ± 1.9%, respectively. At a dosage of 25,000 conidia/larva, larval mortalities for A. gemmatalis and T. ni were 0.4 ± 0.5% and 43.1 ± 8.7%, respectively. Thus, larvae of A. gemmatalis were > 100 times and >200 times more resistant to injected conidia and blastospores, respectively, than were larvae of T. ni. Resistance of A. gemmatalis to N. rileyi may not be solely at the integumental barrier, as is often believed, but may also be a function of an internal physiological response.