Is Isaria fumosorosea selective to Trichogramma pretiosum (Hymenoptera: Trichogrammatidae)?

Abstract

Entomopathogenic fungi and the egg parasitoid Trichogramma pretiosum Riley (Hymenoptera: Trichogrammatidae) might be used together in biological control. However, the effects of these fungi on T. pretiosum are not known. Thus, this study aimed to determine the effect of the entomopathogenic fungus Isaria fumosorosea, on the biological parameters of T. pretiosum. Two isolates of I. fumosorosea (IBCB 367 and IBCB 394) were used for this purpose. (1) In a free choice test: cards (1.0 × 5.0 cm) with non-parasitized eggs of Anagasta kuehniella Zeller (Lepidoptera: Pyralidae) were either sprayed with 0.2 mL of the fungus suspension (1.0 × 109 conidia.mL-1) or with sterile distilled water containing Tween® 80 (0.01%), which were then offered to females of T. pretiosum. (2) No choice test: the isolates were sprayed at a concentration of 1.0 × 109 conidia.mL-1 on cards (1.0 × 5.0 cm) with A. kuehniella eggs. The control consisted of spraying sterile distilled water containing Tween® 80 (0.01%). Individual females of T. pretiosum were confined for 24 h with the cards. The number of eggs parasitized, percentage of emergence, longevity, duration of the egg-adult period and sex ratio were evaluated, as well as the longevity of the females that parasitized the eggs and the mortality of the emerging adults evaluated. IBCB 367 isolate repelled T. pretiosum. The pre-parasitism and post-parasitism sprays did not affect the number of eggs parasitized or the sex ratio, however, the pre-parasitism IBCB 394 treatment the females and males survived for longer, whereas the survival of females in post-parasitism treatment with the same isolate was reduced.The presence of conidia on and mycelium of the fungus in T. pretiosum was confirmed using Scanning Electron Microscopy and a histological analysis. Isolates IBCB 367 and IBCB 394 from I. fumosorosea are selective to T. pretiosum in the laboratory.

Keywords

• hymenoptera
• trichogrammatidae
• trichogramma pretiosum
• isaria fumosorosea
• anagasta kuehniella
• egg parasitoid
• entomopathogenic fungus
• selectivity