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Subject: Entomology × Author: AKSHITA × Start date: 1980 × Thesis Type: M.Sc ×
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    ThesisItemOpen Access
    Influence of soil moisture and organic amendments on infectivity of entomopathogenic nematodes against white grubs
    (Palampur, 2022-11-29) AKSHITA; Chandel, R.S.
    Bioassay studies were done to evaluate the potential of H. indica against white grubs, and to study the effect of soil moisture and organic amendments on virulence of H. indica against I-III instar grubs of B. coriacea. The LC50 values of H. indica were calculated to be 252.77, 286.73 and 320.56 IJs/ml against I-III instars of B. coriacea. There was gradual decrease in susceptibility of grubs with advancement of age to H. indica as indicated by LC50 values. Influence of different substrates was also studied on infectivity of entomopathogenic nematodes. In sand, the LC50 values of grubs (I-III instar) were computed to be 233.33-307.67 IJs/ml. H. indica displayed more or less same virulence, irrespective of soil and sand media used for rearing of grubs. The virulence of H. indica was tested against B. coriacea grubs in soil amended with different organic substrates i.e. cocopeat, vermicompost, vermiculite and FYM in ratios of 9:1, 8:2 and 7:3. In soil:FYM ratio of 9:1, 8:2 and 7:3, the LC50 values irrespective of instars ranged from 277.83-339.14, 243.54-290.26 and 216.08-250.36 IJs/ml, respectively. In different soil:vermicompost ratio of 9:1, 8:2 and 7:3, the LC50 values of H. indica against I-III instar grubs of B. coriacea were calculated in the range of 256.37-345.98, 214.19-282.33 and 168.75-240.53 IJs/ml, respectively. It has been observed that the addition of vermicompost produced more or less similar effects as noticed with FYM. In cocopeat and soil combination, the LC50 values of H. indica against I-III instar grubs ranged from 337.54-545.77, 293.07-455.60 and 247.72-404.65 IJs/ml in the ratio of 9:1, 8:2 and 7:3, respectively. The virulence of H. indica to I-III instar grubs decreased by addition of cocopeat in soil. In different soil:vermiculite combinations, the LC50 values of H. indica against I-III instar grubs were calculated to be 530.83-905.79, 456.93-771.52 and 396.71-668.03 IJs/ml, respectively. Maximum virulence of H. indica was observed in vermicompost, followed by FYM and cocopeat. In the present study, H. indica was tested at three different soil moisture levels of 55, 60 and 65 per cent against B. coriacea. The LC50 values were calculated to be 303.55-394.08, 254.42-361.10 and 231.09-312.91 IJs/ml at 55, 60 and 65 per cent moisture levels, respectively. It has been observed that LC50 values of H. indica decreased with increase in soil moisture.