Toxicity of citrus essential oils against Ceratitis capitata (Diptera: Tephritidae) larvae

Abstract

Citrus peel essential oils are considered to constitute the most important resistance factor of citrus fruits against fruit flies. Essential oils were obtained from three sweet orange varieties, one bitter orange and one lemon variety. Yield, chemical composition and toxicity against neonates of the Mediterranean fruit fly were determined. Based on chemical analysis, the toxicity of commercially purchased major and minor components (monoterpenes and sesquiterpenes) of essential oils was determined. In addition, fractions were prepared to evaluate the role of minor components in the toxicity of crude essential oils. Limonene was by far the most abundant ingredient (96.2-97.4%) in all sweet orange varieties and in bitter orange, while the concentration of limonene was much lower in lemon essential oils (74.3%). Orange and bitter orange essential oils were more toxic than lemon essential oils. The toxicity of orange and bitter orange essential oils was similar to that of their major component limonene. In tests of commercially purchased chemicals, the oxygenated components of essential oils were more toxic than hydrocarbons but their low concentration in citrus essential oils could not affect the toxic activity of essential oils. The presence of α−pinene and β-pinene seems to account for the lower toxicity of lemon essential oils in relation to other citrus essential oils. The importance of understanding the toxicity of essential oils in relation to their composition and their role regarding the resistance of citrus fruits to Ceratitis capitata infestation is discussed.

Toxic and hormetic-like effects of three components of citrus essential oils on adult Mediterranean fruit flies (Ceratitis capitata)

“…Limonene was selected among the three compounds tested because (as mentioned above) it is the most abundant compound of citrus EOs [2, 14]. Subsequently, flies were sorted by treatment and kept in 20 by 20 by 20 cm Plexiglas cages.…”

Essential oils of citrus fruit stimulate oviposition in the Mediterranean fruit fly Ceratitis capitata (Diptera: Tephritidae)

“…A more recent study now recognizes citrus fruit essential oils as the most critical mechanism conferring resistance to citrus species against C. capitata (Papachristos et al , 2008), presumably as a result of the limited ability of females to place their eggs below the toxic flavedo area as a consequence of their short and pointed ovipositor (Jones, 1989; Birke et al , 2006; Papachristos & Papadopoulos, 2009). According to Papachristos et al (2009), apart from the positive relationship between dose‐exposure and mortality effects of citrus essential peel oils on medfly neonate larvae, qualitative aspects of their composition may also affect their effectiveness as a defensive mechanism. In particular, the lower toxicity of lemon essential oil with respect to other citrus oils has been attributed to the presence of substantial amounts of α ‐pinene and β ‐pinene, which exhibit very low toxic activity against larvae (Papachristos et al , 2009).…”

“…According to Papachristos et al (2009), apart from the positive relationship between dose‐exposure and mortality effects of citrus essential peel oils on medfly neonate larvae, qualitative aspects of their composition may also affect their effectiveness as a defensive mechanism. In particular, the lower toxicity of lemon essential oil with respect to other citrus oils has been attributed to the presence of substantial amounts of α ‐pinene and β ‐pinene, which exhibit very low toxic activity against larvae (Papachristos et al , 2009). In addition to differences in the composition of essential peel oils among citrus species as a result of their innate botanical features, a series of studies reports that, during citrus fruit maturation, there are fundamental changes in the composition of the essential oils that largely affect their toxic properties (Attaway et al , 1967, 1968; Greany et al , 1983; Greany, 1989; Rasgado et al , 2009; Flamini & Cioni, 2010).…”

Supercritical CO2 Extraction of Waste Citrus Seeds: Chemical Composition, Nutritional and Biological Properties of Edible Fixed Oils

“…Natural vegetable fixed oils are currently under investigation for their broad‐spectrum in pest control . Moreover, several studies have explored the insecticidal activity of extracts and compounds obtained from Citrus fruits . Data have been reported regarding the interaction of C. capitata with Citrus host species, the toxic activity and hormetic‐like response of Citrus peel essential oils and their most abundant compounds on medfly .…”

“…Moreover, several studies have explored the insecticidal activity of extracts and compounds obtained from Citrus fruits . Data have been reported regarding the interaction of C. capitata with Citrus host species, the toxic activity and hormetic‐like response of Citrus peel essential oils and their most abundant compounds on medfly . Preliminary behavioral bioassays showed that Citrus seed oils had a low attractant effect to medfly, while wet seeds (CRS and CLS) showed a significant attractiveness.…”