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.Ispitivano je prenosenje virusa nuklearne poliedroze (NPV) poreklom iz Autographa gamma (AgNPV), Mamestra brassicae (MbNPV), Lacanobia oleraceae (LoNPV), Helicoverpa armigera (HaNPV) i Xantia c-nigrum (XnNPV) na njihove nezarazene larve pomocu ektoparazitoida Bracon hebetor. Takodje je ispitivano prenosenja virusa nuklearne poliedroze sa visestrukom membranom poreklom iz Spodoptera exigua (SeMNPV) i Spodoptera frugiperda (SfMNPV) pomocu ekotoparazitoida Euplectrus plathypenae. Testirane su dve metode kontaminacije oba parazitoida (izlaganje inficiranim domacinima i ukupne povrsine tela). Takodje su ispitivana dva uzastopna prenosenja virusa pomocu Bracon hebetor na zdrave domacine. Na osnovu dobijenih rezultata moze se zakljuciti da su oba parazitoida mehanicki prenosioci testiranih NPV. Svaka zenka Bracon hebetor je, ukoliko je prethodno bila izlagana inficiranim larvama, bila u stanju da uzastopno dva puta prenese virus testiranih vrsta Noctuidae u iznosu od 27% do 52,2%. Druga metoda kontaminacije (primena suspenzije virusa na celokupnu povrsinu tela parazitoida) je takodje prouzrokovala virusnu infekciju larvi od 29,4 do 54,15%. Parazitoid E. plathypenae je preneo 20% virusa sa inficiranih na larve S. frugiperda koje nisu bile inficirane i 25,57% virusa na neinficirane larve i S. exigua. Pored toga, ustanovljeno je da je 6,43% larvi S. frugiperda i 11,10% larvi S. exigua uginulo kao posledica infekcije virusom. Ista pojava je zabelezena primenom druge metode kontaminacije prilikom koje je ostvareno 33,33% i 40% infekcije, odnosno izmedju 13,23% i 16,67% smrtnosti. Smrtnost svih testiranih larvi izlozenih virusom kontaminiranim parazitoidima bila je visa kada je celokupna povrsina tela parazitoida bila vestacki zarazena virusom u odnosu na parazitoide kojima je prethodno dozvoljeno da polazu jaja u zarazene larve.