Relation of cotton cultivars to the cotton-pest problem in the Sudan Gezira

Abstract

Growing of irrigated cotton in the Sudan, in relation to pest control, entered the ‘crisis phase’ around 1967–68 and the ‘disaster phase’ in 1980–81. At the cruxes of the pest-control problem lay the uncontrollable whitefly-induced lint stickiness and the American bollworm (ABW). The paper gives the succession of cotton varieties in the Gezira and reviews the reports on higher incidence of the whitefly and ABW on newer varieties. Logical explanations offered for the higher pest incidence on newer varieties lead to the conclusion that as compared with Sakel-type cottons, the Lambert-type cottons would have a greater build-up of the whitefly, while Acala cottons would have not only larger populations of both whitefly and ABW but also increased losses from the latter. Changes in area under different types of cotton are shown graphically in relation to the pest-control situation and a case is made for the hypothesis that varietal changes in the Gezira had profound ecological effects which favoured the whitefly and ABW, but made sprays less effective, leading eventually to the cotton-pest-control predicament. Finally, based on recent experience, a hope is expressed that switching to cultivars less favourable to the pests and more suited for efficient pesticide application would ease the cotton-protection problem.