Effect of temperature, time and glycerol concentration on the dehydration and rehydration process of Steinernema carpocapsae and S. feltiae in alginate granule formulation

Abstract

The osmotic responses ofSteinernema carpocapsaeandS. feltiaein terms of dehydration and rehydration in the presence of calcium alginate and formaldehyde were studied. Infective juveniles (IJ) were exposed to different levels of osmotic concentrations, temperatures and dehydration periods and survival of immobilised IJ was quantified. Osmotic responses showed significant differences and the highest numbers of osmotically dehydratedS. feltiaeandS. carpocapsaeIJ were recorded at 14 and 12% glycerol solution, respectively. Mean percentage of rehydrated IJ was significantly higher when dehydration was processed in 22% glycerol solution. Alginate-formulated IJ showed significantly different survival rates depending on the IJ state (dehydrated or non-dehydrated) and the presence of antimicrobial agent. In addition to optimising alginate formulation, the results demonstrate that the concentration of osmotic solution not only determines the percentage of dehydrated IJ, but also their recovery rate during rehydration. By adding formaldehyde, considerable increases were observed in IJ survival.