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Author: BHARATH, AMURI × End date: 2019 × Start date: 2016 × Thesis Type: M.Sc ×
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    ThesisItemOpen Access
    EFFICACY OF ENTOMOPATHOGENIC NEMATODES (EPNs) AGAINST MAJOR INSECT PESTS OF TEA
    (AAU, Jorhat, 2019-07) BHARATH, AMURI; Devi, Gitanjali
    A total 200 soil samples were collected from tea plantation areas of district, Jorhat, Assam and were assessed for entomopathogenic nematodes using the Galleria baiting technique. Out of 200 soil samples, EPNs were found in 2 soil samples with 1% frequency of occurrence. One isolate of Oscheius sp. (0.5%), was isolated from Experimental farm for plantation crops, Section-4, 10, 19 AAU, Jorhat and another Heterorhabditis sp. (0.5%) was isolated from Chetiagoan, Jorhat. Morphological and morphometrical characters were used in the identification of nematode isolates. The identified species were Heterorhabditis bacteriophora, and Oscheius chongmingensis. In infectivity study, indigenous isolates of EPNs, Heterorhabditis bacteriophora and Oscheius chongmingensis tested in the laboratory bioassay, caused mortality of tea mosquito bug, Helopeltis theivora and bunch caterpillar,Andraca bipunctata. Fifty, 60 and 70 per cent mortality of Helopeltis theivora by H. bacteriophora at 150 IJs/insect was observed at 48 h, 72 h and 96h respectively. With the increase in the exposure period to 96 h, H. bacteriophora could induce up to 90% mortality of the tested insect at the dose of 250 IJs. Similarly, mortality of Helopeltis theivora increased with increase in the dosage of O. chongmingensis and recorded 50, 60 and 70 per cent mortality at 200 IJs/insect at 48 h, 72 h and 96h. Bioassay of H. bacteriophora and O. chongmingensis against the 3rd instar larvae of Andraca bipunctata indicated that at 250 IJs/larva recorded 70 and 60% mortality in 48 hours of exposure, while 100 and 90% mortality of Andraca bipunctata was recorded at 96h. H. bacteriophora was more pathogenic than Oscheius chongmingensis against Helopeltis theivora and Andraca bipunctata based on LD50 values at 48 h, 72 h and 96 h.