Relation between energy reserves content and infectivity of the heterorhabditid and steinernematid entomopathogenic nematodes under low soil moisture.

ABSTRACT Three levels of relative soil moisture (10, 5, and 3%) were tested, in sandy loam soil, on the performance of three entomopathogenic nematode species ( Steinernema riobrave , S. rarum , Heterorhabditis indica and the isolate Heterorhabditis sp.) against larvae of Galleria mellonella L. in the laboratory. Virulence, penetration rate and mortality % of the four nematodes were determined. Also, the relation between the energy reserves (total carbohydrates, protein content, and lipids content) in each nematode species and their activity under these ranges of desiccation conditions were investigated. Results demonstrated that the virulence of entomopathogenic nematodes to G. mellonella decreased with increasing of desiccation. Mortality rate was generally low in low-moisture. Heterorhabditis , which had high contents of protein and lipids, recorded highest mortality rate at the control and at the three moisture conditions. However, its penetration rate was highest at the control and at only the 10% soil moisture. As a conclusion, energy reserves content did not benefit entomopathogenic nematodes in desiccation conditions.