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20171
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Subject: Entomology × Author: Debbarma, Dipendu × End date: 2019 × Thesis Type: M.Sc ×
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    ThesisItemOpen Access
    POPULATION DYNAMICS OF APHIDS AND THEIR ROLE IN INCIDENCE ON VIRAL DISEASES OF POTATO, Solanum tuberosum L.
    (AAU, Jorhat, 2017-07) Debbarma, Dipendu; Bhattacharyya, Badal
    Field and laboratory investigations were carried out to know the population dynamics of potato aphids and their role in disseminating viral diseases at Assam Agricultural University, Jorhat during 2016-17. Experimental results delineates the presence of only one species of aphid (Myzus persicae Sulzer) and found active from 2nd week of December, 2016 to 1st fortnight of February, 2017. The lowest (0.19 / leaf) and highest (2.56 / leaf) population of M. persicae was recorded on 15th December, 2016 and on 26th January, 2017, respectively. Correlation studies between weekly mean population of aphids / leaf and different meteorological parameters registered significant negative correlation with the morning (r=-0.843) and evening (r=-0.673) relative humidity. However, other meteorological parameters viz., maximum and minimum temperature, total rainfall and BSSH were found to be non significant. Altogether eight different species of coccinellids viz., Mecraspis discolor (Fab.), Cheilomenes sexmaculata (Fab.), Coccinella transversalis (Fab.), Coccinella septempunctata L., Brumoides suturalis (Fab.), Propylea sp., Harmonia dimidiata (Fab.) and Coelophora saucia (Mulsant) and one species of spider (Neoscona sp.) were recorded during the course of the study. The maximum population of coccinellids (0.32/plant) coincided with the peak aphid population (2.56/leaf). Correlation studies of M. persicae with their aforementioned natural enemies revealed a highly significant positive relationship. Significant negative correlation with morning relative humidity was registered for both cocinellids (r=-0.734) and spider (r=-0.809) population. However, other meteorological parameters viz., maximum and minimum temperature, total rainfall and BSSH were found to be non significant. The first incidence of viral disease was observed after 42 days of sowing of potato and the maximum disease incidence (28.39%) was recorded on 2nd week of February, 2017. Altogether ten alternate hosts of M. persicae viz., Melastoma melabathricum L., Mikania micrantha Kunth, Chromolaena odorata L., Ageratum houstonianum Mill., Solanum nigrum L., Hibiscus rosa-sinensis L., Lycopersicon esculentum Mill., Capsicum annum L., Solanum melongena L. and Spilanthes calva DC. were recorded from the vicinity of the experimental plots. Out of these, potato leaf roll virus was detected only in Melastoma melabathricum L. besides potato leaves and M. persicae.