Fruit fly (Diptera : Tephritidae) ecology in the Western Cape, South Africa

[摘要] ENGLISH ABSTRACT: The Mediterranean fruit fly (medfly) Ceratitis capitata (Wiedemann) and the Natal fly C. rosa Karsch are two important tephritid pest species of commercially grown deciduous fruit in the Western Cape. Detailed information on the status of these two fruit fly species in terms of the influence that different host fruits have on their development, abundance and distribution in this region is not known. This project investigated the status of the two fruit fly species in the Western Cape by a) determining the influence of different fruit types on life table parameters such as egg development, larval development, pupal success rate, adult emergence, fecundity and adult survival, b) assessing trapping data and fruit infestation from home gardens in or near areas where deciduous fruits are grown commercially, in order to determine relative abundances and distribution of C. capitata and C. rosa in the region, and c) using geometric morphometrics to assess variability in development associated with host type, by determining shape variation in the wings of C. capitata that were reared on different host fruits. Life table parameters of C. capitata and C. rosa were determined with a series of laboratory experiments on 'Golden delicious and 'Granny smith apples (Malus domestica L. Borkh.), 'Crimson seedless and 'Dauphine grapes (Vitis vinifera L.), 'Excellence peaches (Prunus persica Sieb. & Zucc.), 'Packham‟s triumph pears (Pyrus communis L.), 'Angeleno plums (Prunus japonica Thunb.), 'Navel oranges (Citrus sinensis Osbeck), clementine (Citrus unshiu Swingle) and 'Fan Retief guava (Psidium guajava Linn.). To gain a broader understanding of the population dynamics of fruit flies, on different commercial and non-commercial host plants in various fruit growing areas during different months of the year, baited traps were installed and fruit infestation of known and potential host fruits were assessed at selected sites. Geometric morphometrics were used to assess shape variation of wings of a F1 generation of C. capitata reared on different host fruits, namely plum, pear and clementine that were of the same varieties as mentioned above.No significant differences (p = 0.773) were found in egg hatch between fruit fly species on the different deciduous fruit types grown commercially in the Western Cape: grape, plum, pear, apple and peach. No positive puncture response was found on oranges, therefore this fruit type was excluded from further analyses. Ceratitis capitata and C. rosa favoured guavas and displayed significant preferences for this fruit in terms of field collected samples and developmental parameters. Developmental success was significantly higher on guavas compared to other fruit types tested, for males and females (p < 0.015), of both C. capitata and C. rosa. Piquanté peppers (Capsicum baccatum L.) and jambos (Syzygium jambos (L.) Alston) were also significant alternate host plants based on high fruit infestation rates in the field and they should be the focus of control actions in home gardens. Patterns of relative abundance of the two fruit fly species were found to adhere to seasonality in terms of host availability and certain abiotic factors such as annual rainfall and elevation. Ceratitis capitata was found to be the dominant species, as has been recorded previously in other studies. Significant differences were found in the wing shape of males and females of C. capitata only. Shape variation was significant for flies reared on different fruit types, more so for males. These results suggest developmental differences for flies reared on different hosts. Results of the present study can be used to gain a better understanding of factors that determine the relative distribution of these two species and which hosts they more readily infest in the Western Cape.Key words: Fruit flies, host, abundance, distribution, development

[发布机构] Stellenbosch University