Thermal control of stored grains insects by utilizing solar energy [Sudan]

Five structures of different geomeetrical shapes made of black galvanized iron were used to study the effect of geometrical shape on heat absorption. All containers (pyramid, cylinder, triangular, rectangular and cube) were filled with sorghum grain and temperature measurements were taken as mentioned above. Different stage of the common insects in Sudan (Tribolium castaneum, Trogoderma granarium and Rhizoperha domonica) were subjected to high temperature (40-45 Daraja C) for different exposure periods to study the effect of heat on life cycle of these insects and to determine the degree lethal for all stages. Quality tests were carried-out for sorghum grains treated at 55 and 70 Daraja C for different exposure periods, to study the effect of temperature and exposure period on sorghum Quality. Highest maximum temperature were observed in black poylthene container (63.9 daraja C) and black metal container (58 Daraja C) when covered with transparent bags. The structures with inclined surface like pyramid and triangular recorded the highest maxium temperatures compared to vertical structures. 45 Daraja C is lethal temperature for all developing stages of these insects investigated when they subjected to such temperature for one and half hour. Treatment of sorghum grains at a temperature of 55 Daraja C for up to two hours did not indicate any harmful effect in all. Storage insect-pests are the major cause of damage and losses in food grain. For prevention of damage and losses by insects infestation, all insects present in the stored product must be eliminated at any stage of their development. Preservation methods which applied to food products for insect pests contro, as chemical method, resulted in several problems and hazard for consumers. Heat treatment is one of the safe alternative measures for storage insects control but it is costy and requires special facilities for application. Therefore, the aim of this study is to utilize solar radiation as soarce of heat for thermal control of storage insects, in an attempt to find out a safer effective control measure at minimal cost. To study the effect of material, black paint, and transparent cover on heat observation, four groups of containers were made from different materials (plastic, polythene, metal and jute) were used. Two containers fromeach group (out of three) were painted black and one from these two black containers was covered with transparent polythene. All containers were filled with equal amounts of sorghum grains and kept out door for exposure to direct sun radiation. Temperature measurements were taken at hours time interval from 8:00 a.m. to 1:00p.m. for the first period and form 1:00 p.m. to 5:00 p.m. for the second period. Studied parameters except moisture content, 1000 kernels weight and bectolitre weight. Treatment of sorghum grains at 55 Daraja C for two hours could be safely used without affecting seed germinability. However, increasing temperature or treatment period could resultted in slight dicrease in germinability. Generally it could be concluded that solar energy could be utilized for control of storage insects with simple treatment of the containers tested in this study under Sudan conditions throughout the year.