Browsing by Author "Rugumamu, Constancia Peter"

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    The response of maize varieties to damage by protephanus truncatus (horn) (coleptera: bostrichidae) in Tanzania
    (University of Dar es Salaam, 1992) Rugumamu, Constancia Peter
    The Larger Grain Borer, Prostephanus truncatus (Horn) (Coleoptera: Bostrichidae} is a major pest of maize on farms in Tanzania. Experiments were conducted, using some commonly grown Tanzanian maize varieties, to determine their ability to resist damage caused by the feeding of P. truncatus. Damage was assessed by counting the number of Fl adults produced in similar infestations of different varieties of maize over the same period of time. The values produced were converted to indices of susceptibility of the maize varieties. Grain weight loss was also used as an indicator of varietal susceptibility to the pest. The experiments were maintained at between 27 and 30~0c and 60-80X Relative Humidity throughout the experimental period. Maize varieties studied included: Kilima; Staha; Kito; TMVI1;; Katumani and ICW. The physical, chemical and nutritional characteristics of the different maize varieties were also measured and compared to determine which of these factors were related to the differences in susceptibility, exhibited by the maize types tested. Laboratory studies showed that P. truncatus is a very damaging storage pest. Differences in the numbers of Fl adults produced were highly significant (P < 0.01) among maize varieties, giving significantly different indices of susceptibility (P < 0.01). Mean weight losses of the varieties were also significantly different (P < 0.05). The most susceptible maize variety, Kilima, produced about twice as many F1 adults as the least susceptible variety, ICW. Insect feeding also caused Kilima to lose about twice as much weight as ICW. There were positive linear relationships between weight loss, and indices of susceptibility; starch content and the indices of susceptibility (regression equations :- y = 8.927 + 0.342x and y = 3.485 + 0.248x respectively). Grain hardness was negatively related to the indices of susceptibility (y = 18.77 - 0.098x). Grain hardness and starch content of the maize were also negatively related .(R = - 0.91). The protein and moisture contents and the grain weight of the maize varieties were not significantly related to the indices of susceptibility. The study shows that those varieties of maize tested had different levels of susceptibility to P. truncatus feeding and that some were less palatable to the insects. It is therefore recommended that further research be carried out with the objectives of producing recommendations for maize with better storage characteristics, by including grain borer resistance parameters in the maize breeding programme, to provide farmers with varieties better able to resist P. truncatus damage:
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    Varietal resistance of stored maize to prostephanus truncatus (horn) (Coleoptera:Bostrichidae) and Sitophilus Zeamais (Motsch.) (Coleoptera: Curculionidae) in Tanzania.
    (University of Dar es Salaam, 2000) Rugumamu, Constancia Peter
    The study objective was to investigate varietal resistance of some stored maize to the Larger Grain Borer (LGB), Prostephanus truncatus and the maize weevil, Sitophilus zeamais in laboratory and field conditions. The studied maize varieties were UCA, CH6, Kilima, Staha, CH3, Kito, TMVI, Katumani. The resistance of the varieties to the pests was measured by using the Index of Susceptibility (IS) which was significantly different ( P < 0.001, 7) among the varieties. Mean weight losses of the varieties were significantly different at P < 0.001. Weights of F adults of each species were the same. Electrophoresis indicated different levels of vitellogenin in haemolymph of the female insects reared on different varieties reflecting varying reproductive performance of the insect species on each variety. The weight losses of the varieties and vitellogenin levels from insects haemolymph exhibited the same trend with the IS of the varieties to the insects. Assessment of a combined effect when P. truncatus and S. zeamais were infesting the same varieties simultaneously exhited varying reproductive performance of the insects at F2. Hardness of the maize grains was negatively correlated with the IS of the variety, r = - 0.979 and - 0.067, P < 0.001 for P. truncatus and S. zeamais respectively. Starch contents of the grains were positively related to IS of both P. truncatus and S. zeamais, r = 0.999 and 0.995, P < 0.001 respectively. Grain hardness and starch content showed negative relationship. Protein and mineral contents of the varieties did not show any influence on the resistance of the varieties to the insects. Field experiments at Wami-Dakawa and Kipera sites revealed the same susceptibility trend of the varieties to the insects as the IS of the varieties in the laboratory. Katumani was the most resistant variety while UCA was the least of them all. It was concluded that P. truncatus was a more damaging insect pest of maize than S. zeamais and that the eight varieties had varying resistance to both pests. A search for more components for Integrated Pest Management (IPM) in grain storage ecosystems was recommended.