Influence of soil type on infectivity and persistence of indigenous isolates of entomopathogenic nematodes, Heterorhabditis indica Poinar et aL (Nematoda: Heterorhabditidae) and Steinernema carpocapsae Weiser(Nematoda: Steinernematidae)

摘要

Entomopathogenic nematodes are now well recognized as potential biological control agents against a wide range of insect pests. Although EPN inhabit the soil, their field application and success depends on soil texture and other abiotic characteristics. Information on the influence of soil variability on the efficacy of EPN is scanty and limited. In view of this, an in vitro study was carried out to examine the influence of soil types on the infectivity and persistence of Heterorhabditis indica and Steinernema carpocapsae with different foraging habits. The pathogenicity and persistence of S. carpocapsae and H. indica varied in different soil types. Virulence of S. carpocapsae PDBC EN 11 was maximum in sandy clay loam soils (I, II and III), clay, sandy clay and sandy soil (I) with 90-100% mortality of wax moth larvae, Galleria mellonella at 24h exposure whereas mortality due to H. indica PDBC EN 13.31 was maximum in soil types of sand, sandy clay, clay, silt and two types of sandy clay loam with absolute mortality within 36h post exposure. The virulence of S. carpocapsae was greater than H. indica in all soil types. Both the nematode species persisted longer in silt and silty clay soils compared to sandy and sandy clay loam soils. Soil type affected nematode infectivity and persistence differentially with lighter soil types favouring virulence and heavier soil types with higher silt fractions favouring persistence over time.