Browsing by Author "Jyothsna Jose."

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    Host suitability and safety evaluation of predominant larval parasitoid of lepidopteran pests in vegetable ecosystem
    (Department of Entomology, College of Agriculture,Vellayani, 2025) Jyothsna Jose.; Manu, C R
    The study entitled ‘Host suitability and safety evaluation of predominant larval parasitoid of lepidopteran pests in vegetable ecosystems’ was carried out in the Department of Entomology, College of Agriculture, Vellayani and farmers’ fields in different districts of Kerala during the period 2022-2024. The main objectives of the study were documentation of larval parasitoids of lepidopteran pests in vegetable ecosystems in southern Kerala and the evaluation of host suitability of the predominant parasitoid and its safety to insecticides and botanicals. Periodical survey was conducted across the various districts of Kerala viz., Thiruvanathapuram, Kollam, Pathanamthitta, Kottayam, Alappuzha, Ernakulam, Kozhikode, Malappuram and Wayanad covering fields of major vegetable crops like cucumber, snakegourd, pumpkin, bhindi, brinjal, and amaranthus. The larvae collected from these fields were reared in the laboratory and observed for parasitisation. Among the lepidopteran pests observed for parasitisation, Diaphania indica Saunders showed maximum susceptibility to parasitoids followed by Sylepta derogate Fabricius with a parasitisation rate of 69.33% and 52.82% respectively. The parasitoids collected were morphologically identified as Bracon hebetor Say, Brachymeria lasus Walker, Apanteles taragamae Viereck and Bracon brevicornis Wesmael. The identification was confirmed with the help of molecular analysis. Out of four parasitoids obtained, B. hebator was designated as the predominant parasitoid since it consistently exhibited highest parasitism in different pests species collected. To identify suitable hosts for the mass production of B. hebetor, a laboratory experiment was conducted using a Completely Randomized Design (CRD) with four treatments and four replications. The hosts selected for the mass production included the rice moth, Corcyra cephalonica Stainton, the greater wax moth Galleria mellonella L, and two natural hosts susceptible to parasitisation, viz., D. indica and S. derogata. The hosts, rice moth and greater wax moth were reared in their respective artificial diet and the natural hosts, cucumber moth and leaf roller were reared in the leaves of respective host plants. The observations on fecundity, emergence period, number of adults emerged, and life stages were recorded. G. mellonella showed significantly higher parasitism (100%), fecundity (20.55), larval emergence (20.55), pupation (20.55), adult emergence (19.66) per host and female progeny (12.6) consistently outperforming C. cephalonica, the common laboratory host for mass production. Contact residual toxicity was assessed using dry film assay to evaluate the safety of B. hebator to insecticides and botanicals. Among the insecticides and botanicals, azadirachtin (5mlL-1) was relatively safer with a maximum parasitoid survival percentage up to 15 HAT followed by KAU Raksha (6gL-1) with survival up to 13 HAT. Although chlorantraniliprole (3ml10L-1) showed survival up to 13 HAT, mortality was observed at 2 HAT. Fenvalarate (2mlL-1) was highly toxic as mortality was observed within 1 HAT. The study identified B. hebetor as the predominant larval parasitoid of various vegetable pests across Kerala. It was also found that D. indica was the most susceptible pest to natural parasitism. B. hebetor was effective against the larvae of other pests viz. Maruca vitrata, Anadevidia peponis, Helicoverpa armigera, Spodoptera litura and Psara basalis under laboratory condition. For mass production of B. hebetor, G. mellonella proved to be the most suitable host followed by C. cephalonica. On safety evaluation, azadirachtin was found to be relatively safer followed by KAU Raksha and chlorantraniliprole.