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Title: Crop phenology based sustainable management of whitefly, Bemisia tabaci (Gennadius) on Bt and non-Bt cotton in Punjab, Pakistan
Authors: Iqbal, Muhammad
Keywords: Agriculture and Veterinary Sciences
Issue Date: 2021
Publisher: University of Agriculture, Faisalabad.
Abstract: The introduction and increasingly widespread use of transgenic cotton, the development of insecticide resistance, selection pressure, and climate change are forcing the need to examine new and alternative management approaches for cotton whitefly, Bemisia tabaci. In present work, field and laboratory studies were conducted during year 2018 and 2019 to evaluate whitefly infestations, CLCuD incidence, molecular characterization of haplotypes, and biorational approaches to the management of B. tabaci. The basic experimental design of field experiment was factorial arrangement of treatments arranged in a split plot with planting date (n=3) and insecticide seed treatment (n=2) randomized at the main plot level and cotton variety (n=4) randomized at the subplot level. In other field experiments, effective entomopathogenic fungi and insecticides were employed as management tools. Field studies showed that early planted (April) cotton had low whitefly population and thus low incidence of CLCuD compared to later planted (May and June) cotton crops. Maximum populations of the whitefly were recorded from late August and September. There was positive relationship between relative humidity and whitefly populations, while temperature and rainfall were not found to be contributing factors. The study found that early planting is more effective in the management of whiteflies and cotton leaf curl virus disease. Planting time and crop phenology ultimately influence pest management, disease prevalence, harvest and yield. Molecular studies indicate that the whitefly population in Punjab province are generally Asia II 1 with at least some MEAM 1 at Rahim yar Khan, hence Asia II 1 is the main cause of CLCuD infestation. Moreover, different associated endosymbionts (Portiera aleyrodidarum, Arsenophonus, Hamiltonella, Cardinium, Rickettsia and Wolbachia) harbouring B. tabaci showed variations in severity when analysed. Cardinium, Arsenophonus and Hamiltonella were detected from each collection location; Wolbachia was present at two of the three locations and no Rickettsia was detected. Laboratory studies tested several entomopathogenic fungi and insecticides against B. tabaci nymphs and adults. Several insecticides were found effective, at recommended doses, for management. Spirotetramat, pyriproxyfen and buprofezin were found effective as nymphicide while flonicamid and diafenthiuron were found effective as adulticide. However, Beauveria bassiana and Metarhizium anisopliae gave equivalent mortality after seven days of the treatment, suggesting that they are slower in action but could be very valuable if applied early. Older insecticides tended to increase population. Conventional insecticides and fungi were not effective against whitefly. The data showed that combining newer insecticides chemistries with entomopathogenic fungi provided better control and return on investment. That is a valuable contribution to pest management in Pakistan. With the use of entomopathogenic fungi and new generation insecticide application, the treated seed of both Bt and non-Bt varieties of cotton, was found to be protected. Main findings of present work include differences among cotton varieties in whitefly preferences, no differences in whitefly pressure between transgenic and non transgenic varieties, and increased profitability associated with April planting dates across location cotton planted in April experienced less pest pressure, had less disease pressure, and maximized financial returns. It is concluded that the phenological based management will promote the cotton growth and will require sustainable management of B. tabaci through biorational (EPF) and new chemistry insecticides (IGRs) application during critical stage of the crop.
Gov't Doc #: 24446
Appears in Collections:PhD Thesis of All Public / Private Sector Universities / DAIs.

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