Browsing by Author "Njenga, G. K"

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    Effect of Transgenic Bt-cotton Variety Bollgard II® 06Z604D Containing cry1Ac and cry2Ab2 Genes on Arthropod Diversity in Confined Field Trials at KARI Mwea, Kenya
    (Egerton University, 2013-01-01) Njenga, G. K; Njinju, S. M; Wepukhulu, S. B; Wessels, W; Waturu, C. N; Kambo, C. M
    A trial to establish effect of Bt-cotton variety, BG II 06Z604D on arthropod diversity was conducted in a confined field at KARI Mwea during 2006/07 cotton growing season. The experiment had nine treatments arranged in a randomized complete block design with four replicates. Three out of the nine experimental plots were sprayed six times to control general sucking pests; three plots were sprayed six times for all arthropod pests and the remaining three received no pesticide treatment. The beneficial arthropod species considered in the current study included the ladybird beetles, parasitic wasp, hoverfly, honeybee, attendant ant, predatory mite and the spider on the other hand to assess the effect of transgenic Bt-cotton on general arthropod species diversity, water, sticky and pitfall traps were set up in four stations across the field, each made up of 3 traps. The results obtained from the trial revealed that the plots sprayed with pesticides to control sucking and general arthropod pests had a negative effect on the beneficial arthropod populations as shown by significantly lower mean arthropod counts in the sprayed plots. However, significantly high arthropod populations were recorded on unsprayed Bt-cotton varieties as compared to the treated isolines and the commercial variety, HART 89M which recorded relatively low populations of beneficial arthropods. The results obtained from this study confirm that transgenic Bt-cotton enhanced population growth of non-target beneficial arthropods and had no detrimental effect on general arthropod species diversity and the environment.
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    Efficacy of Bollgard II® Variety 06Z604D Containing cry1Ac and cry2Ab2 Genes on the African Bollworm (H. Armigera) in Confined Field Trials at KARI Mwea, Kenya
    (Egerton University, 2013-01-01) Waturu, C. N; Wessels, W.,; Kambo, C. M.,; Wepukhulu, S. B.,; Njinju, S. M.,; Njenga, G. K; Kariuki, J.; Karichu, P. M.
    A Confined Field Trial (CFT) was set up at KARI-Mwea with the objective of testing efficacy of Bollgard II® variety, 06Z604D on the African bollworm and non-target pests including the cotton lygus, thrips, aphid and red spider mite. The experiment had nine treatments arranged in a randomized complete block design and replicated four times. The Bollgard II® variety, (06Z604D) compared with the isoline (99M03) and local variety (HART 89M) effectively controlled the populations of the African bollworm. The Bt-cotton variety had no effect on egg laying of African bollworms and achieved less damage of squares. However, the Bt-cotton variety had no significant effect on the populations of the non-target cotton pests. Plots sprayed 6 times for sucking pests on one hand and all pests on the other had lower counts of aphids than the unsprayed plots while the unsprayed plots had lower counts of mites, suggesting that reduced spraying in Bt-cotton could also reduce the populations of mites. The results agreed with the previous results obtained with Bollgard I® Bt-cotton varieties, DP 448B and DP 404BG. Other studies conducted elsewhere with transgenic Bt-cotton also supported the results obtained in the reported work.