The implications of cabbage looper (Trichoplusia ni) : nuclear polyhedrosis virus coevolution for biological control

Many features make nuclear polyhedrosis viruses (NPVs) an attractive alternative to chemicals as insecticides. However, perhaps the single most appealing feature of NPVs is the possibility that one application of virus could lead to long-term control of the pest. This is because following an initial inoculation, viral particles will be released in the environment at each insect generation, assuring a continuous supply of inoculum. Sustained exposure to NPVs is likely to select for resistance. However, in contrast to chemicals, this might not pose such a problem as NPVs can also evolve and become more virulent. Assessing the coevolutionary trajectory of insect-NPV association is thus critical in determining the potential of these viruses as long-term control agents. In my thesis, I examined the coevolution of cabbage loopers (Trichoplusia ni Hubner) and its associated singly-embedded nuclear polyhedrosis virus (TnSNPV). I chose T. ni because it is a generalist herbivore of great economic importance and because it has a short generation time thus making it a good candidate for studies of evolution.