04361nam a22002057a 4500 290660 290660 632.6 FAR/BI PG Farzana M Sha Bioactivity of essential oil from the tea tree Melaleuca bracteata F. Muell. against stored product pests Vellayani Department of Agricultural Entomology, College of Agriculture 2023 97p. MSc The research work entitled “Bioactivity of essential oil from the tea tree Melaleuca bracteata F. Muell. against stored product pests” was carried out at the Department of Agricultural Entomology, College of Agriculture, Vellayani during 2020 to 2022 with an objective to isolate and characterize and evaluate the bioactivity and persistence of toxicity of M. bracteata essential oil against stored product pests viz. red flour beetle, Tribolium castaneum (Herbst) and pulse beetle, Callosobruchus chinensis (Linn.). The essential oil (EO) from M. bracteata was extracted by hydro distillation in clevenger type apparatus. Essential oil yield per 100g leaves was observed as 1.08 mL. The efficacy of tea tree essential oil was tested against the laboratorymaintained culture of T. castaneum and C. chinensis by contact, fumigant and repellent bioassays and the persistence of toxic activity of the essential oil on the test insects were also evaluated under laboratory conditions. In contact toxicity bioassay, the LC50 and LC90 values of the EO against T. castaneum were 25.16 % and 69.94 %, respectively at 24 hours after treatment (HAT). The LC50 and LC90 values of EO against C. chinensis were 0.05 % and 2.73 %, respectively at 24 HAT. In fumigant toxicity bioassay of T. castaneum, the LC50 and LC90 values of the EO were 7.7mLL-1 and 22.95mLL-1 at 24 HAT. The LC50 and LC90 values of EO against C. chinensis were 4.30 μLL-1 and 29.96 μLL-1 , respectively at 24 HAT. In the case of T. castaneum, the maximum repellency observed was 93.75 % at 5% concentration of EO. Cent per cent repellency was not observed here because of the fumigant effect at higher doses which scattered the released insects into both treated and untreated filter paper halves in Petri plates. In case of C. chinensis, the insects get repelled at a very low concentration. 100 per cent repellency was observed at 0.01% and 0.05% concentration of EO after 2 h and 45 min, respectively. The toxic effect of M. bracteata EO persisted up to 34 days on C. chinensis whereas upto 10 days for T. castaneum when exposed to LC90 values obtained from 136 fumigant bioassay. The GC-FID and GC-MS profiling of the EO showed 46 components where, methyl isoeugenol (69.64%) a phenylpropanoid was found to be major component followed by methyl cinnamate (8.73%) and methyl eugenol (7.40%), which may alone or synergistically with other constituents caused the insecticidal effects. Experiments on the effect of the EO on the detoxifying enzymes of T. castaneum and C. chinensis showed that the enzymes like cytochrome P 450, carboxyl esterase were significantly lower in essential oil treated insects, whereas the activity of glutathione S- transferase was found to be higher when compared to untreated insects. Similarly, the total protein content was also found lower in essential oil treated insects compared to the untreated insects. In the present investigation, M. bracteata was found to have a good essential oil yield of 1.08 per cent. The M. bracteata EO showed strong contact, fumigant and repellent toxicity against C. chinensis when compared to T. castaneum. Against C. chinensis, the toxic activity of the essential oil persisted up to 34 days. Methyl isoeugenol (69.53%) was found to be the major component in the essential oil, followed by methyl cinnamate (8.73%) and methyl eugenol (7.41%), which may alone or synergistically with other constituents caused the insecticidal effects. The essential oil in the present investigation has effects on the detoxification enzymes of the test insects. Agricultural Entomology Tea tree Bioactivity of essential oil Melaleuca bracteata F Muell Thania Sara Varghese (Guide) https://krishikosh.egranth.ac.in/handle/1/5810224744 ddc TH 0 0 0 1 TH KAUCLV KAUCLV THESES 2023-10-03 0 632.6 FAR/BI PG 175843 2023-10-03 00:00:00 TH