Population studies on the olive fruit fly, Dacus oleae (Gmel.) (Dipt., Tephritidae) in Western Crete

Abstract

For 4 consecutive years population studies were made on the olive fruit fly in the Sebronas valley which is located at ca 600 m altitude in Western Crete. Olive flies were trapped in olive trees at highest numbers in April‐May and August—October. Fruit infestation was very intense in spring and fall on old fruits left unharvested and new fruits, respectively. Relatively high numbers of flies were also trapped in walnut, cherry, apple and plane trees, in order of preference, and very few in chestnut, arbutus and vine. Very few flies were trapped in the above plants after September, that is in the period olive flies oviposit intensively in the olive fruits. At the beginning of summer, most females had no developed eggs in the ovaries and no sperm was detected in their spermathecae. In the few females that had eggs, the number of eggs per female was much smaller than in spring or fall. During this period the weather is warm‐dry and no olive fruits, old unharvested or new ones, suitable for oviposition exist in the trees. In the 4th year of this study, when no insecticides were applied against the olive fly in the valley due to small crop production, extensive larval mortality was observed in fall due to parasitization. Zusammenfassung Populationsstudien bei der Olivenfliege, Dacus oleae (Gmel.) (Dipt., Tephritidae) in West‐Kreta Vier Jahre hindurch wurden bei D. oleae im Sebronas‐Tal, 600 müber NN, im westlichen Kreta, Populationsstudien durchgeführt. Die meisten Fliegen wurden in den Olivenbäumen von April bis Mai sowie August bis Oktober gefangen. Der Fruchtbefall war im Frühjahr und Herbst entsprechend sehr stark und betraf alte sowie neue Früchte. Relativ viele Fliegen wurden auch in Walnuß‐, Kirschen‐, Apfel‐ und Platanenbäumen (in der Reihenfolge des Befalls) sowie in sehr geringem Maß in Erdbeerbäumen und Wein gefangen. In all diesen Wirtspflanzen wurden nur sehr wenige Fliegen nach dem September gefangen, also zur Zeit der Eiablage der Fliegen in die Olivenfrucht. Zu Beginn des Sommers hatten die meisten Weibchen noch nicht ihre Eier entwickelt, auch waren ihre Samenblasen noch ohne Spermien. Bei den wenigen Weibchen mit bereits ausgebildeten Eiern war die Eizahl pro Weibchen viel geringer als im Frühjahr oder Herbst. Zu Sommerbeginn ist das Wetter trocken‐warm, und die Olivenfrüchte — alte wie junge — sind zur Eiablage nicht geeignet. Im 4. Jahr der Untersuchungen, in welchem im Tal keine Insektizide gegen die Olivenfliege ausgebracht wurden, konnte im Herbst eine erhebliche Parasitierung des Schädlings beobachtet werden.

A basis for the renewal of sterile insect technique for the olive fly, Bactrocera oleae (Rossi)

“…From the 1950s to the 198’s research focused on the biology of OLF, artificial rearing, sterilization, quality control and pilot field testing for application of the SIT to control OLF populations. Gamma‐sterilized, laboratory reared male OLF were released to mate with wild females, yet no effective application of SIT was achieved and SIT was abandoned because of mass‐rearing difficulties (high cost and labour‐intensive), and the low quality of mass‐reared flies (Economopoulos 1972; Economopoulos et al. 1978, 1982; reviewed in Economopoulos 2002).…”

Understanding the seasonal and reproductive biology of olive fruit fly is critical to its management

“…An absence of mature eggs in fly ovaries during the spring and early summer has often been noted in European B. oleae populations (Delrio and Prota 1976;Economopoulos et al 1982;Fletcher et al 1978;Raspi et al 2002;Tzanakakis 1986) and is referred to as a summer reproductive diapause. A similar absence of mature eggs can be induced in flies reared in the laboratory by exposing larvae to cool, short days and adults to hot, long days with no access to olives Tzanakakis 1990, 1993;Koveos et al 1997;Raspi et al 2002;Raspi et al 2005).…”

The use of the cumulative degree-days to predict olive fly, Bactrocera oleae (Rossi), activity in traditional olive groves from the northeast of Portugal

“…egg resorption, fertility index and risk index), which was expected due to the diversity of factors and interactions involved in that suppression. Thus, the absence of female reproductive maturity, which was previously reported as a facultative reproductive diapause (Fletcher et al 1978;Economopoulos et al 1982;Tzanakakis and Koveos 1986;Delrio and Prota 1988;Raspi et al 2005) in response to the change of photoperiod and an increase of temperature (Tzanakakis and Koveos 1986;Koveos and Tzanakakis 1990), could be instead due to quiescence (Daane and Johnson 2010), and is not yet a fully known phenomenon. On the one hand, according to Wang et al (2009), it seems to be primarily controlled by environmental conditions such as temperature and host availability, as well as female 0 s physiological state (e.g.…”