Natural suppression of populations of the leaf folder, Cnaphalocrosis medinalis (Guenee) in fields by an entomogenous fungus, Zoophthora radicans

During a routine search for an alternative to insecticides for the control of rice pests, populations of the leaf folder Cnaphalocrosis medinalis (Guenee) in unsprayed rice fields were found infected with an entomogenous fungal pathogen. The fungus was identified as Zoophthora radicans (Zygomycetes: Entomophthorales). Mortality due to the fungus was 100% both under field conditions as also in green house testing. This fungus, however, did not affect the natural enemy fauna of rice pests in the field. The epizootics of the fungus was consistently high during November-December coinciding with the peak larval eclosion at Karaikal Region. This constitutes a new record from India. The pathogen survived unfavourable season in rice field habitat in the form of resting spores and initiated epizootics in the following year. Thus, the fungus acted as a successful natural suppression agent of the leaf folder population.