ABSTRACT
Pathogens of insects, mites, and plants play an important role as biocontrol agents of many major pests and diseases throughout the world. Sometimes they affect a few individual hosts, but under favorable conditions, whole colonies or populations are affected and many millions of organisms killed developing as an epizootic or epidemic infection. They are generally most effective when host populations are high, in particular where pest density allows easy spread between individuals. A warm, moist environment is particularly important for nematodes and fungal pathogens.
