Some nematodes are beneficial and attack harmful insects, especially soil-inhabiting species. One example is the nematode that is parasitic on mole crickets. It was introduced from South America and has been released throughout Florida. Plate 6 . Microbial agents, or pathogens, are extremely important in naturally occurring biological control.
Beneficial pathogens are very diverse and include fungi, viruses and bacteria.
As the fungus disease progresses, the insect disappears as the mycelium expands over its body. When a fungus disease appears and weather conditions are favorable, an insect population can be drastically reduced in a short time. Plate 8 . Plate 7 . Plate 9 .