Bio-ecology of Entomopathogenic Nematodes
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Date
2013
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Publisher
CCSHAU
Abstract
Out of 90 samples collected from forest plantations (neem, eucalyptus and sheesham), fruit
trees (jujube, guava and citrus) and vegetable crops (okra, onion and tomato), maximum occurrence of
EPNs was found at jujube and okra sites (40% each), followed by neem (30%), while at Dalbergia sp.
and tomato sites only10% sites were found positive. Twelve sites were found positive with
Steinernema sp. and only one with Heterorhabditis sp. In surveillance studies, at site I – Neem
(completely undisturbed ecosystem), site II – Jujube (partially disturbed ecosystem) and site III – Okra
(disturbed ecosystem), Steinernema spp. were recovered throughout the year, except in January and
February. A highly significant correlation was established between soil temperature and per cent larval
mortality of EPNs. When cold stress was given to adult of H. indica and Heterorhabditis sp. (HP
isolate) at 20, 15, 10° C, the development of the nematode to IJs of next generation was not hampered;
but at 5° C the development was stopped at adult stage itself in H. indica but delayed in the other
species. Cold stress given to 1
st
generation juveniles of H. indica reduced IJ emergence and infectivity;
and it was nil at 5° C. In Heterorhabditis sp. (HP isolate) IJ emergence was more but infectivity was
reduced at 15 and 10° C; whereas in Heterorhabditis sp. (HP isolate), adults tolerated the low
temperature, but juveniles succumbed to the cold temperature. Both H. indica and Heterorhabditis (HP
isolate) could not be stored beyond 15 days at 25 ° C. At 20° C, both the species could be stored up to
30 days in sand as well as in tubes without medium, but not in charcoal powder. Maximum period for
which either of these species could be stored was 90 days at 10 or 15° C. Heterorhabditis sp. (HP
isolate) could be stored for a month at 5° C. Triazophos, novaluron, Spinosad, thiodicarb and
imidacloprid were compatibility with H. indica. The per cent survival of IJs ranged from 98.1-100. The
survival was not decreased even after 24 h of exposure.
Description
Keywords
Cold stress, Heterorhabditis indica, insecticides, Steinernema, seasonal occurrence, storage