Effects of Bacillus thuringiensis var. aizawai and NeemAzal-T/S against the immature stages of the African bollworm Helicoverpa armigera (Hübner)(Lepidoptera: Noctuidae)

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Alawad, Loai Mohammed ELamien Ahmed
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The experiments were conducted under laboratory condition at the College of Agricultural Studies, Sudan University of Science and Technology to study the efficacy of Bacillus thuringiensis var. aizawai, NeemAzal -T/S and a combination of 50% Bt.a and 50% NeemAzal-T/S against the second and fourth larval instars of Helicoverpa armigera (Hubner). Three concentrations of Bt.a were used, 0.5 kg/ha, 1kg/ha and 1.5 kg/ha.The results show a significant difference in the mortality percentage between the different concentrations. The Bt.a was more effective in the 4th larval instars, this could be due to the fact that more food was consumed by the 4th larval instars. Three concentrations of NeemAzal- T/S were also used 1L/ha, 2L/ha and 3L/ha. The results showed a significant difference in the mortality percentage between different concentrations. A high repellency effect was observed in the 2nd larval instars and the larvae failed to develop to the next developmental stage. The combination of Bt.a and NeemAzal - T/S resulted in 100% mortality among the 2nd larval instars. This agrees with previous findings that the efficacy of Bt.a is highly effective when mixed with other biopesticides. There is ample evidence that the use of a combination of pesticides that have different mechanisms of actions delays insect resistance, therefore further scientific and feasibility studies should be conducted to evaluate the economic impact of using this combination as a control measure in the future.
University of khartoum