ECOTOXICOLOGY Insecticidal Activity of Citrus aurantium Fruit, Leaf, and Shoot Extracts Against Adult Olive Fruit Flies (Diptera: Tephritidae) E. P. SISKOS, 1 M. A. KONSTANTOPOULOU, 1 B. E. MAZOMENOS, 1,2 AND M. JERVIS 3 J. Econ. Entomol. 100(4): 1215Ð1220 (2007) ABSTRACT Solvent extracts of differing polarity from Citrus aurantium (L.) (Rutaceae) fruit, leaves, and shoots were evaluated for biological activity against adults of the olive fruit ßy, Bactrocera oleae (Gmelin) (Diptera: Tephritidae). Using a petri dish residual exposure bioassay, we found that the petroleum ether extract from fruit alone showed insecticidal activity against the ßies. The extract of the three fruit tissues (ßavedo [peel], albedo, and ßesh) indicated that bioactivity was limited to the ßavedo, and this activity was signiÞcantly higher than that of the whole fruit extract. The most effective extract was obtained when fresh ßavedo was used, whereas extracts of oven-dried ßavedo were inactive. Fruit maturity also affected bioactivity; extracts of ripe fruit were more effective than those of unripe fruit. Our results suggest that C. aurantium ßavedo contains secondary metabolites with insecticidal activity against B. oleae adults. KEY WORDS Rutaceae, plant extracts, botanical insecticides, olive ßy Plants in general are able to produce secondary me- tabolites that are physiologically active to insects and other organisms and that provide the plants with one of the most important defenses in their arsenal (Har- borne 1993, Schoonhoven et al. 1998, Speight et al. 1999, Strauss and Zangerl 2002). These “secondary plant substances” are increasingly being sought for use in integrated pest management (IPM), because they are likely to be more selective and more rapidly de- gradable than synthetic insecticides, and they pose less threat to the environment or to human health (Plimmer 1993, Nair 1994, Isman 2006). Citrus species have been reported as a source of botanical insecticides: Peel and seed solvent extracts from a variety of citrus plants contain secondary me- tabolites that show insecticidal activity against several coleopteran and dipteran species (Su et al. 1972, Ab- bassy et al. 1979, Greany et al. 1983, Sheppard 1984, Salvatore et al. 2004). Limonoids, extremely bitter chemicals present in citrus seeds, act as antifeedants or antagonize ecdysone action in many lepidopteran spe- cies (Klocke and Kubo 1982, Jayaprakaha et al. 1997). All the aforementioned studies focused on the insec- ticidal properties of essential oils derived from peel and seeds. There is little information on the insecti- cidal effects of chemicals derived from other parts of the citrus plant, in particular the leaves, shoots, and ßowers. The overall aim of this study was therefore to com- pare the insecticidal properties of extracts obtained from a range of different plant parts of Citrus spp., speciÞcally the leaves, shoots, fruit, and the tissues of the fruit layers ßavedo (peels), albedo, and ßesh. We chose as study organisms the bitter orange Citrus au- rantium (L.) (Rutaceae), a very common ornamental plant in the Mediterranean basin, and the olive fruit ßy, Bactrocera oleae (Gmelin) (Diptera: Tephritidae), a very serious pest that continues to inßict major yield losses in the same region, despite repeated pesticide treatments (Katsoyannos 1992). We also aimed to re- solve the best solvent system for extracting the bio- active chemicals, and whether fruit maturity and oven-drying of plant tissues affected the biosynthesis and the degradation of the bioactive components. Materials and Methods Plant Material. All plant materials used in this study were collected from bitter orange trees located in the Zografos area of Athens, Greece. Ten healthy trees were selected for sampling. The trees were of similar size (4 Ð5 m in height) and 10 yr old. In each sam- pling the same number of fruit, leaves, and shoots was collected from each tree. Samples were rapidly trans- ferred to the laboratory and cleaned thoroughly by washing in detergent and then rinsing with tap water followed by distilled water. Extraction Procedure. Before extraction, plant ma- terials were homogenized in methanol (1 ml/g fresh plant material or dried equivalent to 1 g of fresh [=0.35 g dry]) for 5 min in a blender. The homogenate was then placed in a 2-liter Erlenmeyer ßask, and methanol (MeOH) (20 Ð22°C) was added (Þnal extraction vol- ume, 1 liter). The ßask was then placed on a shaker. The conventional solid-liquid extraction method in- 1 Chemical Ecology and Natural Products Laboratory, NCSR “De- mokritos,” P.O. Box 60228, 153 10 Aghia Paraskevi, Attikis, Greece. 2 Corresponding author: e-mail: bmazom@bio.demokritos.gr. 3 Cardiff School of Bioscience, Cardiff University, P.O. 195, Cardiff, United Kingdom. 0022-0493/07/1215Ð1220$04.00/0  2007 Entomological Society of America