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Title: Toxicity of microbial insecticides and chlorantraniliprole for the control of Helicoverpa armigera (Hubner) on chickpea
Authors: Tahir, Muhammad
Keywords: Entomology
Issue Date: 2017
Publisher: University of Agriculture, Faisalabad.
Abstract: The Helicoverpa armigera is a voracious and economically important insect pest devastating chickpea crop all over the world. To combat these pests the mainstay of the farmers are the use of conventional chemical insecticides, against these insecticides resistant has developed. The current study aimed at evaluation of microbial entomopathogens and new chemistry insecticide coragen against H. armigera. The study consisted of a series of experiments to screen different fungal isolates of Beauveria bassiana Metarhizium anisopliae s.l. to pick potential isolates against larvae of H. armigera, to evaluate the capacity of B. bassiana to colonize endophyticallyand their integrated use with Bacillus thuringiensis against H. armigera, to check the effectiveness of entomopathogenic nematode Heterorhabditis bacteriophora Poinar, B. bassiana and M. anisopliae alone and integrated manners, while sequential applications of H. bacteriophora were made after fungal treatment. Finally these agents were deployed under field conditions to determine their effect on survival of natural allies, pod infestation and the effect of treatments on the yield of chickpea. Four isolates of B. bassiana (WG-11, WG-12, WG-16 and WG-18) and one isolate of M. anisopliae (WG-44) exhibited greater virulence against both 2nd and 4th instar larvae among 22 tested isolates. These isolates revealed lowest LC50 and LT50 values. Beauveria bassiana colonize endophytically in chickpea plant very successfully and synergistic interaction (CTF≥20) was recorded at the moderate dose of B. thuringiensis and endophytic B. bassiana when fed with fungal inoculated chickpea leaves. Moreover, both agents have detrimental effects on pupation, adult emergence, egg eclosion and the developmental parameters of H. armigera. The toxic nature of microbial agents also influenced the diet consumption, frass production and weight gain. In combined treatments of entomopathogenic fungi and H. bacteriophora additive to synergistic interactions were recorded. The degree of addictiveness and synergism increased with delayed application of H. bacteriophora. These treatments also significantly affected pupation, adult emergence, egg eclosion and developmental parameters of H. armigera. The toxic nature of microbial agents also influenced the diet consumption, frass production and weight gain. Integrated application of B. bassiana, B. thuringiensis and coragen were made on chickpea under field conditions. Maximum marginal return was obtained in integrated application of B. thuringiensis + coragen treatments compared to their sole application. Microbial agents in simultaneous application are proved to be effective in lowering the larval density of H. armigera and hence lowering the yield losses. Microbial agents are relatively safe to natural enemies of H. armigera and hence proved to be eco-safe agents. Maximum marginal return was obtained in combined application of microbial agents than their individual application. Moreover, newer chemistry insecticides exhibit unique mode of action and better environmental profile that could help to rotate or replace the older insecticides.
Gov't Doc #: 15711
Appears in Collections:PhD Thesis of All Public / Private Sector Universities / DAIs.

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