Baculovirus insecticide production in insect larvae

Abstract

Baculovirus-based insecticides are currently being used worldwide, and new products are in development in many countries. The most dramatic examples of successful baculovirus insecticides are found in soybean in Brazil and cotton in China. Production of baculoviruses is generally done in larvae of a convenient host species, and the level of sophistication varies tremendously between field-collection of infected insects at the one extreme and automated mass manufacturing at the other. Currently, only products with wild type baculoviruses as active ingredients are commercially available. Baculoviruses encoding insecticidal proteins are considered attractive, especially for crops with little tolerance to feeding damage, where speed-of-kill is an important characteristic. Successful field tests with such recombinant baculoviruses have been done in the past, and more tests are ongoing. However, low-cost production of recombinant baculovirus in larvae poses specific problems, due to the short survival time of the production host. In this chapter, benchtop-scale production of two typical baculoviruses is described. First, we describe the production of wild type Helicoverpa zea nucleopolyhedrovirus in bollworm (H. zea) larvae. H. zea larvae are very aggressive and need to be reared in isolation from each other. Second, we describe the production of a recombinant Autographa californica multiple nucleopolyhedrovirus in the non- cannibalistic cabbage looper, Trichoplusia ni. The recombinant baculovirus encodes the insect-specific scorpion toxin LqhIT2. The tetracycline transactivator system enables the production of wild-type quantity and quality product while toxin expression is repressed since normal toxin production would result in premature death of the production host that would limit progeny virus production.