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Abstract
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Entomopathogenic nematodes from families Heterorhabditidae and Steinernematidae and their symbiotic bacteria Photorhabdus and Xenorhabdus respectively, are one of the most effective insect pests biocontrol agents. These biological weapons are usedto control several agriculturally important insect pestssuch as Plutella xylostella as a one of the most important pest of family Brassicaceae. Increasing the shelf life of EPN based products is one of the major challenges in extensive application of these elements. With the aim of increasing EPNs longevity, survival rate and its stability against extreme environmental conditions researches are continuously undertaken in different laboratories to develop new formulations. Among different introduced methods, formulations which have been developed based on anhydrobiotic potential of infective juveniles are promising ones. During anhydrobiosis, IJs water content decline severely and metabolism rate and oxygen consumption shrink. In this research, survival rates of three species of EPNs including H. bacteriophora, S. carpocapsae and S. feltiae in alginate gel formulation were evaluated in different thermal regimes (8, 15 and 25 °C). After 3 months, 80% of infective juveniles of S. feltiae survived at 8°C, for 15°C and 25°C treatments this rate was 70.56% and 79.78% respectively. In all thermal treatments,highestsurvival rates (92.73%, 89.62% and 86.03%) were recorded for infective juveniles of S. carpocapsae and lowest ones for H. bacteriophora (82.12%, 75.92% and 73.23%).Bioassay experiments clearly showed the susceptibilities of last instar larvae and pre-pupa to infective juveniles of evaluated entomopathogenic nematodes.
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