Microbial Biopesticides: Protozoa
Protozoa are single-celled eukaryotic organisms that exist in both water and soil. While most protozoa feed on bacteria and decaying organic matter, a wide range of protozoan species are insect parasites.
For example, the protozan Nosema locustae is known to be a natural biocontrol agent of many grasshopper species. Nosema infects at least 90 species of grasshoppers. It is non-toxic to humans and other mammals, as well as the over 250 natural predators of grasshoppers. Nosema is particularly important in areas where environmental issues preclude use of traditional insecticides.
Grasshoppers cause millions of dollars of damage to forage crops each year. Nosema locustae has been developed into a commercially available grasshopper control agent that infects and weakens young grasshoppers and adversely affects female grasshoppers’ ability to reproduce.
After consuming Nosema locustae, grasshopper feeding is typically curtailed within a week. Within two weeks or longer, as many as 50% of the infected insects die and approximately half of the surviving population remains weak, consuming 75% less forage than a healthy insect.
Grasshoppers are notorious scavengers. An important function in the transmission of Nosema spores to healthy grasshoppers occurs as the insects scavenge and cannibalize infected cadavers. Since infected grasshoppers develop a large number of the spores within them, the cannibalizing grasshoppers get a much greater dose of the disease causing organism than through the initial Nosema application.