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

Thesis (MScConsEcol)--Stellenbosch University, 2015.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, developmentAFRIKAANSE OPSOMMING: Die Mediterreense vrugte vlieg (medvlieg) Ceratitis capitata (Wiedemann) en die Natal vlieg C. rosa Karsch is twee belangrike tephritid pes spesies van kommersiële bladwisselende vrugte in die Wes-Kaap. In diepte inligting oor die status van hierdie twee vrugte vlieg spesies in terme van die invloed wat verskillende gasheer vrugte op die ontwikkeling, volopheid en verspreiding van hierdie vlieë in die Wes-Kaap het, is nie bekend nie. Die huidige studie ondersoek die status van hierdie vrugte vlieg spesies in die Wes-Kaap deur a) vas te stel wat die invloed is wat verskillende vrugte op lewens tabel parameters het soos eier ontwikkeling, larwe ontwikkeling, papie sukses, volwasse opkoms, vrugbaarheid en volwasse oorlewing, b) deur gebruik te maak van lokval data en besmette vrugte vanaf tuine van huise, wat naby of in areas voorkom waar vrugte kommersieel gegroei word, sodat daar vasgestel kan word wat die relatiewe volopheid en verspreiding van C. capitata en C. rosa in hierdie streek is, en c) om geometriese morfometriese metodes te gebruik om vas te stel wat die verskille in die ontwikkeling van die vrugte vlieë is wanneer hul op verskillende tipes gasheer vrugte geteel word, deur te kyk na verskille in die vorme van die vlerke. Lewens tabel parameters was vasgestel vir “Golden delicious” en “Granny smith” appels (Malus domestica L. Borkh.), “Crimson seedless” en “Dauphine” druiwe (Vitis vinifera L.), “Excellence” perskes (Prunus persica Sieb. & Zucc.), “Packham‟s triumph” pere (Pyrus communis L.), “Angeleno” pruime (Prunus japonica Thunb.), “Navel” lemoene (Citrus sinensis Osbeck), naartjies (Citrus unshiu Swingle) and “Fan Retief” koejawels (Psidium guajava Linn.) deur „n reeks van laboratorium eksperimente. Lokvalle was uitgesit en vrugte was versamel in die tuine van huise wat in of naby areas is waar vrugte kommersieel gegroei word, om „n breër kennis te verkry van die dinamika agter die vrugte vlieg populasies op verskillende kommersiële en nie-kommersiële gasheer plante, tydens verskillende maande van die jaar. Geometriese morfometriek was gebruik om die verskille in die vorme van die vlerke van „n F1 generasie C. capitata wat op verskillende gasheer vrugte geteel was te bepaal, naamlik pruime, pere en naartjies. Hierdie vrugte was dieselfde variëteite as die bogenoemde vrugte. Daar was geen aansienlike verskille (p = 0.773) in die uitbroei van eiers, tussen die vrugte vlieë spesies, wat uit verskillende gasheer vrugte wat kommersieel in die Wes-Kaap gegroei word (druiwe, pruime, pere, appels en perskes) versamel was nie. Geen steekmerke was waargeneem op lemoene nie en om hierdie rede is geen verdere analises op lemoene gedoen nie. Ceratitis capitata en C. rosa het koejawels verkies en het aansienlike voorkeur vir dìe vrug betoon in terme van vrugte wat in die veld versamel was, en ontwikkelings parameters. Die ontwikkelings sukses was aansienlik hoër vir koejawels teenoor ander vrugte wat getoets was vir beide mannetjies en wyfies (p < 0.015) van C. capitata en C. rosa. Piquanté rissies (Capsicum baccatum L.) en jambos (Syzygium jambos (L.) Alston) was aansienlike alternatiewe gasheer plante wat tydens veldwerk versamel was en moet die fokuspunt vorm van beheer aksies in huise se tuine. Patrone in die relatiewe vespreiding van die vlieë is beïnvloed deur seisonale patrone in terme van die beskikbaarheid van gasheer plante, en sommige abiotiese faktore soos reënval en hoogte bo seespieël. Ceratitis capitata was die dominante spesie, soos al reeds voorheen vasgestel was tydens ander studies. Aansienlike verskille is waargeneem in die vorme van die vlerke van slegs C. capitata mannetjies en wyfies. Daar was aansienlike variasie in vlerk vorme vir vlieë wat op verskillende vrugte tipes geteel was, meer so vir mannetjies vlieë. Die resultate dui daarop dat verskille in die ontwikkeling van vlieë voorkom wat op verskillende gasheer vrugte geteel word. Die resultate van die huidige studie kan dus help om beter te verstaan watter faktore die relatiewe volopheid en verspreiding van hierdie vrugte vlieë beïnvloed. Dit kan ook help om die tipe gashere wat meer geredelik aangeval word beter te bepaal vir die Wes-Kaap. Sleutelwoorde: Vrugte vlieë, gasheer, volopheid, verspreiding, ontwikkelin