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Subject: Agricultural Entomology × Author: Alka Sherief × End date: 2019 × Start date: 2017 × Thesis Type: M.Sc ×
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    ThesisItemOpen Access
    Bioefficacy of the acaropathogen, acremonium zeylanicum (petch) gams and evans against the spider mite, tetranychus truncatus ehara (acari: tetranychidae)
    (Department of Agricultural Entomology, College of Horticulture, Vellanikkara, 2017) Alka Sherief; KAU; Haseena Bhaskar
    Spider mites (Prostigmata: Tetranychidae) cause severe injury to vegetables grown under both protected and open field conditions. Awareness on the ill effects associated with the use of synthetic chemicals in pest management has resulted in an increased demand for safe to eat food. Hence, ecofriendly strategies for the management of mite assume high priority. Investigations on potential natural enemies of spider mites by All India Network Project on Agricultural Acarology (AINPAA) have identified an acaropathogenic fungus, Acremonium zeylanicum (Petch) Gams and Evans from the spider mite, Tetranychus urticae Koch on brinjal from Thrissur district. The present study was undertaken at the Department of Agricultural Entomology, College of Horticulture, Vellanikkara during 2016 - 2017 in the above context to investigate the biocontrol potential of the acaropathogen, A. zeylanicum against the predominant species of spider mite in Kerala, Tetranychus truncatus Ehara; to assess the sensitivity of the acaropathogen to selected novel acaricides and botanicals and also to evaluate its safety to the predatory mite, NeosAcremonium zeylanicum was evaluated along with two novel acaricides and two botanicals against T. truncatus on cucumber under polyhouse conditions. A. zeylanicum significantly reduced mite population seven days after treatment at both 1×108 spores ml-1 (72.71%) and 1×107 spores ml-1 (55.03%). However the novel aceiulus longispinosus (Evans). Laboratory bioassay conducted to evaluate the efficacy of A. zeylanicum at five different concentrations viz.1×105, 1×106, 1×107, 1×108 and 1×109 spores ml-1 against T. truncatus recorded more than 50 per cent mortality of adult mites within six days at both 1×108 and 1×109 spores ml-1. The mortality increased with increase in concentration of the fungus and also with progress in time. The highest mortality of 68.36 per cent was recorded by A. zeylanicum applied at the rate of 1×109 spores ml-1 seven days after treatment, which was on par with 61.65 per cent mortality recorded at 1×108 spores ml-1. The fungus was more effective against adult stage compared to egg stage of T. truncatus. The highest mortality of egg stage (41.33%) was recorded four days after the treatment at 1×10 9 spores ml-1. aricides (spiromesifen & diafenthiuron) and botanicals (neem oil & azadirachtin) were significantly superior to the acaropathogen in reducing the mite population. Compatibility study of A. zeylanicum with different agrochemicals revealed that the acaricides, spiromesifen and fenpyroximate were relatively safer to the fungus. The fungicides, Curzate M8 (Cymoxanil 8% + Mancozeb 64 %) and Equation Pro (Fomaxadone 16.6%+ Cymoxanil 22.1%) recorded highest per cent inhibition and were followed by the acaricides, fenazaquin, diafenthiuron, propargite and the botanicals azadirachtin and neem oil. Laboratory evaluation of safety of A. zeylanicum to the predatory mite N. longispinosus showed that the predatory mite was less susceptible to A. zeylanicum than the prey mite, T. truncatus. The pathogen did not have any ovicidal effect and had caused much lower mortality of 20 per cent on adults of N. longispinosus at the highest dose of 1×108 spores ml-1. The study indicated the potential of A. zeylanicum in reducing mite population significantly both in laboratory and polyhouse. The pathogen was found to be compatible with commonly used acaricides and also was safe to the predominant predatory mite species in vegetable ecosystems. Thus it can be inferred that the acaropathogen A. zeylanicum could be a valuable component in integrated mite management programme in vegetables.