Influence of Initial Pest Density on the Survival and Development of Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae) in Broken grains of Three Physiological types of Pearl Millet and Nine Cultivars of Wet Season Sorghum
N.E.S. LALE and B.M. SASTAWA
ABSTRACT: The effects of three pest densities (5, 10 and 155 pairs of adult beetles/5 g of broken grains) on the survival and development of rust-red flour beetle (Trtbolium castaneum) using cereal diets processed from three physiologically different millets and nine
sorghum cultivars were assessed under tropical storage conditions. The maiwa millet diet was the most preferred both for survival and progeny development of T. castaneum in comparison with dauro and gero millets. The proportion of adult beetles that died and
the mean number of larval and adult progeny that developed on a maiwa diet were 30.8% and 52.3, respectively. Comparable figures for dauro and gero millets were, 37.4% and 49.0, and 48.1% and 25.7, respectively. The initial pest density of 30 adult
beetles/5 g of broken grains significantly suppressed progeny development in millet in comparison with development at pest density of 10 or 20 adult beetles/5 g of broken grains. The mean numbers of T. castaneum progeny that developed at the pest densities of 10, 20 and 30 adult beetles/5 g of broken millet grains were 44.4, 44.3 and 3g,4·, respectively. In sorghum, the proportion of T. castaneum adults that died (46.5%) was
significantly higher in broken grains of Chakalari-red than in those of any of the other cultivars except Janna-jos. Mortality of adult flour beetles was lowest (15.9%) in broken grains of Jigari-red. Mean number of T. castaneum progeny that developed in broken sorghum grains ranged, on average, from 34.0 in Tumbuna-fadama to 43.7 in Chakalari-red. In contrast, progeny development in sorghum increased significantly with increasing initial pest density being 29.3, 39.4 and 48.5 at pest densities of 10, 20 and 30 adult beetles/5 g of broken grains, respectively.