• The Korean Journal of Soil Zoology
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• v.5 no.2
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• pp.97-100
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• 2000

We report here an improved collecting method of the infective juveniles multiplied in the host insect with the entomopathogenic nematodes, Steinernema carpocapsae Weiser. The specific characteristics of this method involved the opening of the host insect hemocoel after the population of their infective juveniles reached at the maximum (6 days at 25$\^{C}$ after nematode treatment to nonimmunized host insects) to facilitate the escape of the multiplied nematodes. It also used 'Baermann funnel'method to select the infective juveniles effectively. This improved 'Baermann funnel'method was compared with a traditional collecting method, which was characterized with a combination of untreated host insects and 'White trap'collecting method, in both yield and pathogenicity of the collected infective juveniles to the fifth instar larvae of beet armyworm, Spodoptera exigua (H bner). More than 95% of the nematode populations collected by the two methods represented the morphological infective juveniles. To prove the nematodes to be infective juveniles functionally, pathogenicity and infective activity were compared in the nematodes collected by the two methods. They were not different in both pathogenicities and infective activities which were measured by the numbers of nematodes penetrated into the hemocoel of the insect hosts after exposure for the specific times to the same dote of infective juveniles. Significant difference between two collecting methods was found in the total yields of the infective juveniles per host insect About 50,000 infective juveniles per infected fifth instar larva of S. exigua after 6 day incubation at 25$\^{C}$ were collected only for 2 days by the improved 'Baermann funnel'method, while about 20,000 infective juveniles per host were collected for 10 days by the classical 'White trap'method.