University of Khartoum

Studies on Some Trypetidae of Economic Importance in the Sudan

Studies on Some Trypetidae of Economic Importance in the Sudan

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Title: Studies on Some Trypetidae of Economic Importance in the Sudan
Author: Ali, El Tigani El Tahir
Abstract: A study of distribution, relative importance and some aspects of the biology and ecology of the fruit flies (Trypetidae) was carried out. A survey conducted in the semi arid northern parts of the Sudan, for two seasons, revealed the occurrence of nine species, of which at least five are economically important. Dacus (Diadacus) ciliatus and D. (D.) vertebratus are the major pests of cucurbits in the country causing extensive damage to cucurbits; of the two the former was the dominant species. The Mediterranean fruit fly, C. capitata and an allied species, C. quinaria were responsible for considerable losses to citrus fruits in the Northern Province. A fifth species, Acanthiophilus helianthi was noticed to injure safflower inflorescence for the first time in the Sudan. A comparative study of the morphology of the four Dacus species was done and the distinguishing characters were brought out. D. ciliatus was found quite distinct from D. vertebrates, and three 'forms' with gradations of hypo-pleural spots were distinguished. The biology of D.cilliatus was studied in the field and laboratory. The total life cycle occupied 16-17 days under laboratory conditions (25-27°c and 60-75% R.H.). The larva underwent three moults with four larval instars; two were visible, while the last one was inside the puparium. Adults of D. cilliatus had no resting stage under Sudan conditions. Fecundity potential, as determined by oviposition, indicated that it is capable of laying an average of 143 eggs, with a maximum of 433 eggs. Adult flies lived up to 7 months, when fed with honey, sugar granules and water. Host preference tests in the field indicated that there was no definite preference for any of the varieties under test, although 'khiar' (Cucumis sativus) was generally preferred for egg laying. Among the synthetic attractants tested, cuelure was the most efficient as far as D. cilliatus is concerned, while trimedlure was found quite attractive to the Mediterranean fruit fly Ceratitis capitata, and not to its related species C. quinaria. Seasonal activity of adults of D. ciliatus studied by using Steiner's traps showed the maximum activity during the cold months (November – January), which coincided with the main growing season of cucurbits. Preliminary tests to find out the depth of pupation using different soil types, showed that the average depth was 3.3cm. in clay, 1.7 in sandy soil and 1.2cm in silt soil. D. ciliatus was found to prefer young fruits for oviposition, but there was heavy mortality of larvae in small, young fruit; the life history was shorter when immature stages were reared on young fruit. The atmospheric Relative Humidity exercised very little influence on the emergence of flies from the puparium in the soil. Based on the preliminary studies conducted, some recommendations for control under Sudan conditions and lines of future work are indicated.
URI: http://khartoumspace.uofk.edu/123456789/16934
Date: 2015-11-08


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