05104nam a22002057a 4500 290653 290653 632.6 ASH/BI PG Ashish V V Bioefficacy of Tagetes minuta L. against Teranychus truncatus ehara (Prostigmata: Tetranychidae) and Aphis craccivora koch (Hemiptera: Aphididae) Vellanikkara Department of Agricultural Entomology, College of Agriculture 2023 xi, 66p. MSc The spider mite, Tetranychus truncatus Ehara and the black cowpea aphid, Aphis craccivora Koch are two predominant sucking pests infesting several vegetable crops in Kerala. Farmers depend heavily on chemical pesticides for the management of these pests. However, due to the adverse effects of synthetic pesticides on environment and non-target organisms, there is a growing need for environmentally benign alternatives. This has generated interest in the development of biopesticides, based on botanicals. Tagetes minuta L., commonly known as Mexican marigold or wild marigold or southern cone marigold is a plant whose pesticidal properties have been well documented. The study was carried out in the Department of Agricultural Entomology, College of Agriculture, KAU, Vellanikkara during 2020-2022. The objectives of the study were to identify the bioactive fractions of T. minuta and to evaluate the bioefficacy of the solvent fractions against T. truncatus and A. craccivora. Tagetes minuta plants cultivated in the Department of Floriculture and Landscaping, were harvested at the flowering stage followed by shade drying and grinding. The powdered botanical was extracted sequentially using hexane (non-polar), chloroform (medium polar) and water (highly polar) as solvents. The hexane, chloroform and aqueous fractions of T. minuta were evaluated for their efficacy against T. truncatus and A. craccivora in the laboratory at five different concentrations viz., 0.025, 0.05, 0.1, 0.15 and 0.2 %. The ovicidal and adulticidal effects of the solvent fractions were evaluated against T. truncatus by topical application method. Considerable ovicidal action was exhibited only by hexane fraction at higher concentrations (0.1, 0.15 and 0.2 %), with cent per cent egg mortality at 0.2 %, after 120 h of treatment. However, all the three solvent fractions caused appreciable mortality of adult mites, in a concentration dependent manner. The hexane fraction at 0.2 % and 0.15 % were significantly superior, causing 91.67 and 90.00 per cent mortality, respectively, followed by 0.2 % chloroform (66.67), 0.15 and 0.10% (56.67), and 0.2 % aqueous fraction (53.33), after 120 h of treatment. The efficacy of the solvent fractions (0.025, 0.05, 0.1, 0.15 and 0.2 %) against A. craccivora was evaluated in the laboratory on cowpea seedlings grown in paper cups. Though the highest reduction in aphid count after 120 h of treatment was recorded in hexane fraction at 0.2 % (90.00 per cent), chloroform (86.67) and aqueous fraction (85.00) also recorded reduction in aphid count on par with it, at the same concentration. Qualitative phytochemical analysis of the hexane and chloroform fractions was carried out by GC-MS/MS to identify the major bio- active constituents. The two compounds, 4-o-methylphorbol 12, 13- didecanoate and milbemycin b were found in both the fractions, while 4α-phorbol 12,13-didecanoate was found in hexane fraction only. The best concentrations of the three botanical fractions of T. minuta were tested for efficacy against T. truncatus on potted plants of amaranthus along with neem oil emulsion (2%) and horticultural mineral oil (2.5%). After 14 days of treatment, the hexane fraction recorded the highest reduction in mite population (88.78 %) followed by chloroform and aqueous fractions which were on par with each other (77.97 and 76.96 %, respectively). Hexane fraction was superior to neem oil emulsion, while chloroform and aqueous fractions were found to be on par with neem oil emulsion (76.44), which is a widely recommended botanical preparation for mite pest management in different crops. The best concentrations of the three solvent fractions of T. minuta identified in the laboratory study were evaluated against A. craccivora on cowpea, in a pot culture experiment. By 10th day of treatment, the field efficacy of hexane fraction (78.95 % reduction) was comparable with that of neem oil emulsion (87.59 %), while chloroform (72.43 %) and aqueous fractions (68.20 %) were comparable with azadirachtin 1 EC (67.97 %). The results of the study indicate that Mexican marigold possess excellent acaricidal and insecticidal properties and that the plant can be explored further, for utilization in the management of spider mites as well as aphids. Agricultural entomology Tagetes minuta L Teranychus truncatus Aphis craccivora Haseena Bhaskar (Guide) https://krishikosh.egranth.ac.in/handle/1/5810213725 ddc TH 0 0 0 1 TH KAUCLV KAUCLV THESES 2023-09-27 0 632.6 ASH/BI PG 175845 2023-09-27 00:00:00 TH