Browsing by Author "Minja, Eliaineny Mose"

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    Effect of intercropping sorghum and cowpea on their lepidopteran stem and pod borer populations build-up with particular emphasis on ChiloPartellus (swinhos) (Lepidoptera: pyralidae) in South Kenya.
    (University of Dar es Salaam, 1990) Minja, Eliaineny Mose
    Polyculture of intercropping is widely practiced in Eastern Africa. Normally crops with widely differing growth habits such as legumes and cereals are interplanted. Such crop mixtures may however, lead to increased or decreased pest incidences depending on crop combination, location, season and cropping pattern. The results described in this thesis involved field studies on sorghum stem and cowpea pod borers in relation to cropping patterns and microclimatic factors in 1986-88. Five cropping patterns were investigated: cowpea and sorghum monocrops, cowpea and sorghum sown simultaneously in the same plot, and cowpea sown before and after sorghum in the same plots. Crops were planted in randomized blocks replicated thrice at ICIPE Mbita point field station (MPFS) and on a farmer’s field on Rusinga Island. Chilopartellus (Swinhoe) (Pyralidae) egg counts were made on twenty sorghum plants. Chilo moths were released on caged field plants to study oviposition. Sorghum plants were artificially infested with eggs to study larval establishment. Stem borer larval and pupal populations were monitored on destructively sampled sorghum plants. Pod borer egg and larval counts were made weekly. Pupae were sampled every five days. Dead borers and other arthropods on plant samples were noted. Soil arthropods were sampled weekly using pitfall traps to monitor potential predators. Light intensity was recorded at ground level using a quantum radio meter (LI-1905). Canopy temperature and humidity were recorded. C. partellus, Busseolafusca (Fuller) (Noctuidae), Eldanasaccharina (Walker) (pyralidae) and Sesamiacalamistis (Hmps.) (Noctuidae) were recorded on sorghum throughout the study. Stem borer larval and pupal populations appeared to increase with the age of sorghum. Monocrop sorghum had a significantly higher number of borers and leaf damage than intercrops. There was a significant delay in borer colonization and establishment on sorghum sown after cowpea than the other cropping patterns. Monocrop cowpea had a significantly higher number of Marucatestulalis (Geyer) (Pyralidae) eggs, larvae, pupae and damaged pods than intercrops. Borer colonization and establishment was delayed in cowpea sown after sorghum. Diseases and parasites were the predominant mortality factors in larvae and pupae respectively. Soil arthropods were fewer in sorghum monocrop than intercrops. Furthermore, light intensity, temperature and humidity variations within crop canopies were higher in monocrop than intercrops. Cowpea and sorghum grain yields seemed to have been adversely affected by late planting. However, it appeared that if both crops are to be produced efficiently on a piece of land, then cowpea could be sown before sorghum. In conclusion therefore, intercropping appeared to have substantial influence in disrupting borer colonization and establishment as well as favoring predators and parasites.