They are limited to certain kinds of insects, and have been found to be effective biological control agents against several other kinds of insect pests that live in the soil. (articles.orlandosentinel.com)
Lately Brazilian scientists have had the best success in developing biological control agents of plant - eating mites. (sciencedaily.com)
Predatory mites have been used as biological control agents for years. (sciencedaily.com)