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Abstract
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ABSTRACT
Limited shelf life of entomopathogenic nematodes severely restricts
their use in biological control programs. In a series of experiments,
the dehydration and rehydration response of Heterorhabditis
bacteriophora infective juveniles (IJs) was investigated under a
range of glycerol concentrations, temperatures and incubation
periods. Based on the outcome of these initial studies, nematodes
dehydrated using the optimal process were formulated in alginate
granules to understand how these nematodes would undergo
survival formulation in a model carrier. The highest rate of
osmotically arrested IJs occurred in the 22% glycerol solution
(98.06%). IJ recovery was considerably improved when
dehydration was processed at 10% glycerol solution and 15°C. By
trapping IJs in calcium alginate, depending on the adjuvants, the
survival rate of IJs differed significantly. IJ state (dehydrated or
non-dehydrated) and the addition of formaldehyde had a
profound effect on IJ viability, though the severity of the effect
varied was dependent on whether the IJs were alginate
formulated. Among different formulations, the highest viability
(84.18%) was observed where dehydrated IJs were formulated in
alginate granules containing formaldehyde. The results showed
that the concentration of osmotic solution not only determines
the percentage of dehydrated IJs but also affect their subsequent
recovery in an aqueous environment. Overall, the results indicate
that the shelf life of formulated IJs is significantly affected by
combination effects of a broad range of factors. Then
understanding the interactive mode of actions of involved factors
in formulation play a critical role in developing and introducing
more efficient formulations.
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