Transmission of different nucleopolyhedroviruses by two ectoparasitoids: Bracon hebetor say (Hymenoptera: Braconidae) and Euplectrus plathypenae (Howard) (Hymenoptera: eulophidae)

Abstract

The transmission of nucleopolyhedroviruses (NPVs) of Autographa gamma (AgNPV), Mamestra brassicae (MbNPV), Lacanobia oleraceae (LoNPV), Helicoverpa armigera (HaNPV) and Xantia c-nigrum (XnNPV) to their relevant larvae by the ectoparasitoid Bracon hebetor and the transmission of the multiple-enveloped NPVs of Spodoptera exigua (SeMNPV) and Spodoptera frugiperda (SfMNPV) by the ectoparasitoid Euplectrus plathypenae was examined. Two methods of contamination of the both parasitoids (exposure to infected hosts and total body surface) and two subsequent transmissions of the viruses by Bracon hebetor to healthy hosts were tested. The results showed that both parasitoids were capable to be mechanical vectors of the tested NPVs. Every Bracon hebetor female was able to transmit subsequently twice the virus in 27% to 52.2% of the five Noctuidae species by preliminary exposing to infected larvae. The second method of contamination (applying virus suspension to the total body surface of the parasitoid) was also efficient causing virus infection in between 29.4% and 54.15% of the larvae. The parasitoid E. plathypenae transmited the virus from infected to noninfected larvae in 20% and 25.57% of the S. frugiperda and S. exigua larvae, and 6.43% and 11.10%, respectively of them died from the virus infection. The same observation was established by the second method of contamination - respectively 33.33% and 40% infection and between 13.23% and 16.67% mortality. The mortality of all tested larvae exposed to virus contaminated parasitoids was higher when the parasitoid entire body surface had been artificially contaminated with the virus than when the parasitoid itself was previously allowed to oviposit the larvae.