n African Entomology - Comparing abundance of predacious and phytophagous mites (Acarina) in conjunction with resistance identification between Bt and non-Bt cotton cultivars

Volume 21, Issue 1
  • ISSN : 1021-3589



Knowledge of the arthropod complex associated with any crop is essential for developing pest control strategies. Bt (GK-12, Lu-23 and SGK-321) and non-Bt (Zhong-12, Shiyuan-321 and Simian-3) cotton varieties were used for assessing differences in harbouring populations of the carmine spider mite (Boisduval) and predatory mite (Oudemans). Two Bt cotton varieties GK-12 and Lu-23, and two non-Bt varieties Zhong-12 and Simian-3 appeared more supportive for maintaining , whereas, SGK-321 (Bt) and Shiyuan-321 (non-Bt) clearly showed reduced pest susceptibility, but efficient in maintaining population. Throughout the study period, the densities of remained higher (1.77 and 1.40 per leaf) in Bt than non-Bt varieties following insecticides application against the cotton pest complex. The beneficial mite remained active in both Bt and non-Bt varieties, but Bt cotton had slightly higher numbers of the predator (0.58 per leaf) than non-Bt cotton (0.40 per leaf). Consequently, there were no great impacts on the predatory natural enemy associated with Bt cotton and the predator population in Bt fields was not negatively affected in comparison with conventional cotton. All tested varieties of cotton significantly differed in relation to their morphological characteristics. Of the different factors found to affect the populations of predacious and phytophagous mites, in general, the trichome density on the lower surface of the leaf, leaf thickness and plant height had positive relations with arthropod abundance. Our results showed that SGK-321 (Bt) and Shiyuan-321 (non-Bt) could be recommended for use in creating new resistant cotton varieties as a component of an integrated pest management strategy. Hence, the differences in the response of pest and predator to host plant and leaf architectures should be considered to enhance their roles in biological control strategy.

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