With increasing problems of resistance to chemical pesticides amongst cotton pests, especially Heliothis, more attention is being given to biological control agents, including pathogens. Pathogens are often more compatible with chemicals than predators and parasitoids, and many can be formulated and sprayed in the same manner as chemicals. In addition, some can be easily grown using mass fermentation techniques. They are usually completely harmless.to man, domestic animals and other biocontrol agents. However, much work remains to be done on the ecology and physiology of these pathogens, as well.as on the technical aspects of production, formulation and application.