Soil as an Environmental Reservoir for Baculoviruses: Persistence, Dispersal and Role in Pest Control

Baculoviruses are DNA viruses that can naturally control insects and form the basis for a range of biological insecticides. These viruses are occluded in a crystalline protein matrix, the occlusion body (OB), which favors their persistence in the environment until consumed by a susceptible insect. This review presents evidence that baculoviruses are perfectly adapted to persist in soil. In support of this assertion, detailed evidence is presented concerning the stability of virus OBs in soil, the mechanisms and processes that affect OB transport to soil, OB persistence and movement through the soil layers, and the transport of the virus back to the host's foodplant for subsequent transmission. The soil reservoir interacts with the host insect, the foodplant and the biotic and abiotic factors in the environment, all of which influence the function of the soil OB reservoir. Agricultural practices that conserve the soil reservoir can result in improved pest control. The soil is also an overlooked source of genetic diversity for the design of baculovirus-based insecticides. Finally, the principal issues that remain to be elucidated are highlighted, particularly with reference to those that affect the soil-baculovirus relationship and the impact of the soil OB reservoir on insect populations.