Studies on the Biology of the Red-flour beetle Tribolium castaneum Herbst., (Coleoptera: Tenebrionidae) in different cereal flours

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Adil Shareif Mohamed Khair
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University of Khartoum
Experiments were conducted at the Entomology Laboratory of the Faculty of Agriculture, University of Khartoum, Shambat, Sudan. Chemical analysis of the four cereal flours was carried out at the Biochemistry Laboratory of the Faculty of Agriculture, University of Khartoum. The objectives were to study the biology of the red flour beetle Tribolium castaneum Herbts., when reared on flours of sorghum, wheat, millet and rice and to investigate the relative susceptibility of these four cereal flours to infestation by this pest.. Morphological studies of T. castaneum on sorghum flour were carried out and the egg, different larval instars, pupae and adults were described. The average length of the fully grown larva, pupa and adult were 5.84, 4.00 and 4.52mm, respectively. Life-cycle studies of T. castaneum at uncontrolled laboratory conditions, have shown that, egg incubation, larval, pupal and total developmental period in sorghum flour were significantly different. The total development period varied considerably according to the prevailing environmental conditions particularly the temperature. Thus the shortest durations were recorded in June (higher temp.) and the longest in September and October (lower temp.). The biology of T. castaneum was studied on wheat, millet, sorghum and rice flours in uncontrolled laboratory conditions. The flour type (food) had a significant effect on the total developomental duration of the beetle. Millet was the most favourable and rice was the least favourable for the development of the different stages of the beetle. Also food had a significant effect on the body mean weight of the different stages of the insect. The mean weight of larva, pupa and adult were less for insects reared on rice flour than for those reared on wheat flour. The ratio of males to females, sex ratio of T. castaneum was close to unity on sorghum flour, greater than unity on both millet and wheat flours, but less than unity on rice flour and with predominance of males. Studies have shown that, on the basis of total progeny of T. castaneum produced and the percentage of weight loss in the infested cereal flours, none of the cereal flours was completely resistant to infestation. However, response to infestation varied significantly from one ceral flour to the other. Significant differences in percentage weight loss in each month over a period of three months were recorded in flours of wheat, millet, sorghum and rice. Considering weight loss as the main indication of susceptibility, rice appeared to be the least susceptible (lowest total percentage of weight loss), while wheat and millet flours were the most susceptible (highest total percentage of weight losses). Insect population increased significantly on wheat and millet flours (most suitable), when compared to that on the flour of the other two cereals, particularly rice flour (least suitable). For the chemical composition of the different flours, the differences between their moisture content were not significant. Differences in protein content were highly significant, however, protein contents of wheat and millet were the same and significantly higher than that of sorghum and rice. Also ash and oil contents among the four flours were significantly different. The differences between carbohydrate contents of the flours were significant with rice showing the highest level and millet the lowest. Lower amounts of ash, oil and proteins were found in rice flour than in the other three flours, this may explain why T. castaneum was not able to develop and multiply faster on rice flour. Generally, the study showed the ability of T. castaneum to survive and complete development in all four types of the cereal flours
A thesis Submitted in partial fulfillment of the requirements for the degree of M.Sc.(Agric.)
Biology Red-flour beetle cereal flours Crop Protection University of Khartoum
Adil Shareif Mohamed Khair, Studies on the Biology of the Red-flour beetle Tribolium castaneum Herbst., (Coleoptera: Tenebrionidae) in different cereal flours .- Khartoum : University of Khartoum, 2002 .- 106p. : illus., 28cm., M.Sc