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

Abstract

Female Mediterranean fruit flies (medfly) Ceratitis capitata (Wiedemann) (Diptera: Tephritidae) perceive both qualitative and quantitative aspects of citrus fruit chemistry. However, the behavioural and biological adjustments of this response remain largely unknown. In the present study, the ovipositional responses of gravid female medflies to essential oils (i.e. the most critical resistance factor to medfly infestation) of various citrus fruits are investigated. In dual‐choice (treatment versus distilled water control) experiments, females lay significantly more eggs into pre‐punctured hollow oviposition hemispheres (domes) provided with 1 µL of citrus peel oil from sweet orange, satsuma mandarin, bitter orange, grapefruit and lemon compared with odourless domes. No‐choice tests show a weak effect of lemon essential oils in stimulating oviposition. The female ovipositional response to sweet orange oil (the most active in eliciting oviposition) is dose‐dependent. Additionally, limonene, the most abundant chemical in all citrus oils, stimulates oviposition, whereas linalool, a representative compound of immature citrus fruit associated with high toxicity against immature stages of fruit flies, has a significant deterrent effect. In further no‐choice tests, females lay approximately 23% fewer eggs in limonene (93%) (amount found in orange oil) and 60% fewer eggs in limonene 93% plus linalool 3% (approximately 10‐fold the amount found in orange oil) mixtures, relative to sweet orange oil. The results suggest that the limonene content accounts largely (but not completely) for the ovipositional responses observed in sweet orange oil, whereas high linalool proportions are capable of significantly masking and/or disrupting its stimulatory effects in citrus oils. The importance and practical implications of these findings with respect to understanding how citrus fruit chemistry influences the ovipositional responses of medfly is discussed.

Oviposition of fruit flies (Diptera: Tephritidae) and its relation with the pericarp of citrus fruits

“…This fact was observed by Ioannou et al (2012) who identified that compounds like linalool, found in different contents in citrus, is associated with mortality of immature stages of C. capitata, while limonene, found in more than 90% in all citrus oils, stimulates oviposition justifying infestations of C. capitata in citrus fruits.…”

“…The flavedo constitution is cited by several authors as the most critical resistance mechanism to fruit flies infestation in citrus (Back and Pemberton, 1915;Greany et al, 1983;Salvatore et al, 2004;Ioannou et al, 2012). Possibly, when oil glands in the flavedo are broken, they release toxic compounds that, in contact with eggs and first instar larvae, can cause death before the larvae reach the albedo region (non-oily region of the peel) (Greany, 1989).…”

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.…”

Plant Odors as Fruit Fly Attractants

“…As citrus fruits mature from an immature green to an orange/yellow mature stage, the linalool content of the peel oil declines progressively, and the less toxic limonene becomes the major component. Limonene content acts as a potential stimulus for the ovipositional responses observed with sweet orange oil, whereas high linalool contents could mask or disrupt those effects in citrus oils (Ioannou et al 2012).…”

“…Limonene, the most abundant chemical in citrus essential oils, stimulates oviposition in C. capitata females, whereas linalool, a compound representative of immature citrus fruit associated with high toxicity against immature stages of fruit flies and considered as an important compound conferring resistance against fruit fly larval development, has a significant deterrent effect (Ioannou et al 2012). As citrus fruits mature from an immature green to an orange/yellow mature stage, the linalool content of the peel oil declines progressively, and the less toxic limonene becomes the major component.…”