Preliminary studies on the winter season abundance and fitness of tephritid fruit flies in the Harare area, Zimbabwe
Bara, Gracian Takudzwa
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Fruit flies (Diptera: Tephritidae) are among the major constraints in commercial fruit production in many developing African countries. Due to their economic importance, knowledge of the tephritid fruit fly spectrum in any given area is a prerequisite for the development of an integrated pest management programme (IPM) to address the pest problem. To determine the diversity and abundance of fruit fly species in Harare and its environs during the winter season, assessments were conducted on avocado (Persea americana ), naartjie (Citrus reticulata ), guava (Psidium guajava ), lemon (Citrus limon ) and orange (Citrus sinensis ) in the cold months of April to August 2013. Traps baited with methyl eugenol and a 3-component lure (Biolure®) were used to trap adult fruit flies at different locations. A total of 4,991 fruit flies were collected from the traps. In decreasing order of abundance, the fruit flies recorded comprised the following: Ceratitis rosa (56.4%), Bactrocera invadens (21.4%), Ceratitis cosyra (11.4%) and Ceratitis capitata (10.9%). Overally, guava fruit trees recorded the highest number of fruit flies caught/trap/day. Traps set up in avocado trees captured higher numbers of C. cosyra compared to those set up in guava trees. Laboratory incubation of field-sampled fruits yielded C. capitata , C. rosa , C. cosyra and B. invadens . Ceratitis capitata was observed to co-habitate with C. rosa and C. cosyra in guava and naartjie fruits, whilst B. invadens co-habitated with C. rosa and C. cosyra in guava fruits. The fruit infestation indices varied with fruit type with the highest infestation being recorded in guava where C. rosa and B. invadens numbered 13 and 15 flies per kg of fruit, respectively. Trirhithrum sp. was also observed to emerge from naartjie fruit at 0.53 flies per kilogramme of fruit. Guava and naartjie were identified to be the main overwintering hosts for C. cosyra whilst B. invadens utilized guava. The adult tephritid populations, in particular, B. invadens , C. rosa , C. cosyra and C. capitata , were generally low during winter and this vi presents the most opportune time to suppress the fruit fly populations. The influence of host fruit and temperature on the body size (and hence fitness) of field populations of C. cosyra was also investigated. Ceratitis cosyra adults reared from guava fruits sampled at the end of the summer season were generally larger than those reared from winter-sampled naartjie and guava .