University of Khartoum

The Biology and Ecology of Some Important Insect Pests of Stored Dates in Central Sudan

The Biology and Ecology of Some Important Insect Pests of Stored Dates in Central Sudan

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Title: The Biology and Ecology of Some Important Insect Pests of Stored Dates in Central Sudan
Author: El Nazir, Susan Mohamed Abdalla
Abstract: Life history studies of the date moth, Ephestia calidella, the saw-toothed grain beetle Oryzaephilus surinamensis and the merchant beetle Oryzaephilus mercator reared on different date cultivars were conducted under ambient laboratory conditions at the Agricultural Research and Technology Corporation, Shambat. Beside the life history aspects: susceptibility, food preference and warehouse studies on stored dates were also carried out. The latter study was conducted in an adjacent warehouse within the ARTC buildings. All these investigations were run during the year 2001 to 2003. The various life history aspects studied were in general proved as essential elements in the development of these insects when Gondaila was provided as food. The highest mean number of eggs per female (fecundity) for Ephestia calidella was 172.9 and the longest oviposition period was 5.5 days and the life span of adults was 7.4 days. These were recorded at a mean temperature and relative humidity of 22.7°C and 34.3% in wintertime (December). Poor performance in egg laying and other parameters were recorded at a mean temperature and relative humidity of 35.5°C and 19.5% (May) and of 33.5°C and 59.8% (August). Humidity was found to play a minor role on the above aspects studied. The same trend in the results and under ambient similar conditions (temperature and relative humidity) was more or less attained when Barakawi was given as food. The shortest mean larval-pupal development period on Gondaila was 36.3 and 41.2 days at a mean temperature and relative humidity of 29.2°C and 39.8% (October-November) and the longest was 94.1 and 120.0 days at 34.9°C and 39.2%R.H. (May-November) in continuous darkness and natural day length, respectively. On Barakawi the shortest period was 61.4 and 63.4 days at a mean temperature and relative humidity of 26.2°C and 37.4% (October-January) and the longest was 101.7 and 147.0 days at 34.9°C and 39.2%R.H. (May-November) in continuous darkness and natural day length, respectively. The intrinsic rate of natural increase was calculated for E. calidella. The highest value was 0.873 at 29.2°C and 39.8% R.H. (October-November) on Gondaila. However, on Barakawi the highest value was 0.571 at 33.1°C and 45.3% R.H. (October-January). With regard to Oryzaephilus surinamensis the pre-oviposition period, fecundity and oviposition period were markedly affected by temperature, relative humidity and date cultivars (Barakawi and Gondaila). The highest mean number of eggs was 61.2 the oviposition period continued for more than 9 months when the experiment was started in August (warm and humid month), some adults lived for up to 10 months. Low temperature prolonged the incubation period while relative humidity seemed to have little effect. However, both temperature and relative humidity affected egg hatching. The shortest larval-pupal mean development periods 21.4 and 31.0 days were recorded at a mean temperature and relative humidity of 36.3°C and 49.9% (August-September) on Gondaila and Barakawi, respectively. The longest mean period was 54.5 days on Gondaila, however, the mortality was 100% on Barakawi at a mean temperature and relative humidity of 25.0°C and 32.4% (January-March). For Oryzaephilus mercator the highest mean fecundity was 32.7 eggs when the experiment was conducted in August. The oviposition period was extended up to 3 months. Some adults lived for about 5 months. The shortest mean larval-pupal development period was 26.2 days on Gondaila and 36.2 on Barakawi at a mean temperature and relative humidity of 36.3°C and 49.9% (August-September). The longest mean period was 48.3 days on Gondaila at 33.5°C and 19.5% R.H. (March-May). However, on Barakawi the mortality was 100%. Inter-specific interactions between O. surinamensis and O. mercator were investigated at 30°C and 70=485;75% R.H. using the replacement series design. Predictions of the outcome of competition from the first generation based on the design were verified by long-term experiments. O. surinamensis was dominant over O. mercator which was eventually eliminated. Susceptibility and food preference experiments were performed. Gondaila was found to be the most susceptible cultivar, followed by Bit-Tamoda, Mishrig Wad Khateeb, Mishrig Wad Laggai and Barakawi was the least susceptible for both E. calidella and O. surinamensis. For O. mercator Bit-Tamoda then Gondaila, Mishrig Wad Laggai, Mishrig Wad Khateeb and also Barakawi was the least susceptible. The succession and population growth of the stored date insects was investigated in a warehouse studies From November, 2001 to December, 2002. E. calidella was prevailing during the cool drier months. However, O. surinamensis was prevailing during the warm humid months of the year.
Description: December 2004221 Pages
URI: http://khartoumspace.uofk.edu/handle/123456789/10973
Date: 2015-05-18


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