Protozoa in Bio-controls of Crop Pest
The protozoa subphrla Sporozoa and onidospora contains numerous entomophilic protozoans and most promising examples in biological insect pest suppression programmes. The effects of protozoan infections are chronic rather than acute and they may affect their hosts over a fairly long time period. Because of this, disease is often manifested in the host insect only by a reduction vitality, fecundity and life span.
The naturally occurring epizootics of protozoan disease in insect pest like European corn borer, some Lepidoptera, several species of flies, aquatic Diptera including mosquitoes and grasshoppers. The Neogregarires occurs primarily in the fat body and intestinal tract of Coleoptera, Lepidoptera, Hemiptera and Diptera. Mettasia grandis is an important pathogen of the cotton boll weevil and showed considerable promise. Mettaisa frogodermae was studied and used in pest suppression programme of khapra beetle.
The infective spores are totally empty. The emerging sporozoites and motile in the gut tract and soon penetrate the gut to the haemocoel and infect cells of susceptible tissues within 2 days. The diseased larvae die early within a week and shrivel so badly that they are used for spore production, Nosema locustae also attacks grasshopper or locust species and spores and applied in bran bait.