Kavya Yadhav G A creator Haseena Bhaskar (Guide) text Vellanikkara Department of Agricultural Entomology, College of Horticulture 2018 monographic 52p. Spider mites of the family Tetranychidae are devastating pests of horticultural crops demanding suitable control measures. Synthetic acaricides, while effective, often cause resistance and resurgence, besides leaving residues on fruits and vegetables. Consequently, several natural products are being evaluated as safer alternatives for the management of mite pests. Petroleum derived mineral oils, for instance, have been used for centuries against insect and mite pests in several crops. However, phytotoxicity concerns have limited their use to a few selected crops. Recent advances in processing of mineral oils have mitigated these apprehensions, enabling their wider application in crop pest management, including vegetables. A study was undertaken at Department of Agricultural Entomology, College of Horticulture, Vellanikkara during 2017-18 in order to evaluate the bioefficacy of horticultural mineral oil (HMO) against the spider mite, Tetranychus truncatus. The study also aimed to test the phytotoxic effect of HMO on okra and its safety to important natural enemies such as the predatory mite, Neoseiulus longispinosus and the acaropathogenic fungus, Acremonium zeylanicum. Laboratory bioassays were conducted to evaluate the efficacy of HMO alone and in combination with neem oil against eggs and adults of T. truncatus. The results showed that HMO had appreciable ovicidal and adulticidal action against T. truncatus. Mineral oil alone, at concentrations of 1.5, 2.0, 2.5 and 3.0 per cent and combinations of HMO with neem oil viz., HMO 2.5 per cent + neem oil 2.0 per cent; HMO 3.0 per cent + neem oil 2.0 per cent and HMO 1.0 per cent + neem oil 1.0 per cent recorded 100 per cent mortality of eggs. In the case of adults, HMO at 3.0 per cent recorded the highest mortality of 92.00 per cent and was significantly superior to HMO at 2.5 per cent (84.00%) and neem oil 2.0 per cent (81.33%), which were on par with each other. In the field experiment, plots treated with HMO at 2.5 (92.60%) and 3.0 per cent (93.90%) as well as HMO 2.5 per cent + neem oil 2.0 per cent (94.14%) and HMO 3.0 per cent + neem oil 2.0 per cent (96.79%) recorded significant reduction in mite population and were superior to plots treated with either spiromesifen (91.08%) or neem oil alone at 2.0 per cent (90.42%). The phytotoxic effect of HMO was tested on 45 day old potted okra plants by foliar application at concentrations of 2, 3, 4, 5 and 6 per cent. None of the concentrations showed phytotoxic symptoms on okra. Laboratory bioassay to evaluate the safety of HMO to the predatory mite, Neoseiulus longispinosus revealed that HMO is relatively safer to the predator than to T. truncatus. HMO at 3.0 per cent killed 38.89 per cent of eggs while HMO 3.0 per cent + neem oil 2.0 per cent caused the highest mortality (27.78%) in adults. Combinations of HMO with neem oil were found to be more inhibitory to the acaropathogen, Acremonium zeylanicum than HMO alone. HMO 3.0 per cent + neem oil 2.0 per cent recorded significantly higher inhibition of 86.44 per cent as against a significantly lower 46.67 per cent inhibition by HMO at 2.5 per cent. The high efficacy of HMO against the spider mite T. truncatus as well as its relative safety to the predominant natural enemy brought out in the study suggests that HMO can be an effective tool for mite management in vegetable crops. MSc Agricultural Entomology 632.6 KAV/BI http://krishikosh.egranth.ac.in/handle/1/5810144232 http://krishikosh.egranth.ac.in/handle/1/5810144232