Cabbage Looper 1 Nuclear Polyhedrosis Virus-Parasitoid Interactions

Field and laboratory tests were conducted to determine the relationships between a parasitoid, Voria ruralis (Fallen), its host, Trichoplusia ni (Hübner), and a nuclear polyhedrosis virus. By dissection it was observed that up to 100% of the parasitoidism of field-collected T. ni larvae was in hosts infected with nuclear polyhedrosis virus. Thus, accounting for parasitoidism in diseased hosts can significantly alter apparent parasitoidism rates. Laboratory tests confirmed that the parasitoid can survive, develop in, and emerge from diseased larvae. Although histological sections revealed nuclear polyhedrosis virus in the gut lumen of V. ruralis puparia that had fed on diseased hosts, the virus was voided from adults soon after emergence and before oviposition. Tests revealed that V. ruralis does not act as a biological vector, and it acts as a mechanical vector only under very restricted conditions.