| dc.description.abstract | Manila (Sclerocarya birrea) is one of the most useful indigenous trees in Africa. The fruits of marula are used to produce useful products such as juice, jam and beer. The seed kernels are very rich in proteins and can be processed into oil. The wood is carved to make pestles, mortars, bowls and saddles. The bark of the tree is used to make fibers, dyes and medicine. However, the marula tree is attacked by various diseases and pests. Of particular importance are the fruits which are attacked by fruit flies. Fruit flies cause extensive loses to various fruit tree species throughout the world, for example in Kenya, as much as 80% of mango yield have been lost to fruit flies. A lot of work has been done on the pest status and diversity of fruit flies on various cultivated fruits around the world but little has been done on indigenous fruit trees in Botswana. Thus this work was carried out to evaluate the pest status and diversity of fruit flics on marula trees in three localities (Gabane, Mochudi and Rasesa) in Botswana. Traps with four different parapheromones and a food bait were placed on 15 randomly selected marula trees in the three sites to study the fruit fly diversity. The traps were cleared once every two weeks to gather all the accumulated flics. Pest status of fruit flies on marula fruits was evaluated using three categories of marula fruits which were randomly selected. Fifteen to twenty fruits which showed symptoms of infestation, those without symptoms and fruits that fell to the ground under marula trees were collected to evaluate pest status of fruit flies in marula tree. Ten fruits randomly selected from each category and from each site were dissected to count the immature stages. Some fruits were also set up in the laboratory for fruit fly emergence. Five fruits from each category and from each site were set up for adult emergence. After emergence the adult fruit flies were fed on marula fruits until their natural colour developed fully. The adults were killed and used to identify the species of fruit flies that infest manila. A total of 3835 adults of 14 fruit fly species were collected from the sites from December 2009 to March 2010. The fruit fly species recorded from traps in this study were C. cosyra, C.9 capitata, C. rosa, C. pedesiris, C. quinaria, D. ciliatus, D. emi/tus, D. frontalis, D. fuscalus, D. percropsis, D.vertebratus, Coelotrypes species, Trirhithrum species and Isocania species. Gabane had the most diverse fruit fly species composition with Shannon index of 1.333, followed by Rasesa with an index of 0.651 and Mochudi with 0.279. Ceratitis cosyra was the most abundant species, making up 61.5% of all the specimens collected from the three sites. Fruits collected from the ground had the largest number of damage symptoms when compared to fruits obtained from the trees. The fruits from the ground also had the highest number of immature fruit flies when compared to fruits from the trees. However, fruits with symptoms of infestation collected from the tree had the highest number of adult fruit fly emergence. Among all the fruit fly species collected only C. cosyra emerged from the fruits. Among the lures used, biolure was the most efficient as it attracts both males and females of different fruit fly species. The results in the study add to the fruit fly pest list found in Botswana and can be used by concerned departments in the Ministry of Agriculture of the Government of Botswana especially the National Plant Protection Division in the development of pest management and control programmes. The scientific community worldwide will also find the information usfteful. The information can also be useful to farmers and other organizations which deal with production and trading of fruits such as the Horticultural Market of Botswana. Further research is needed to determine the economic threshold of fruit flics on marula and also to determine the fruit fly species diversity in different host crops in the whole country. | en_US |
