Influence of some olfactory and optical properties of fruits on host location by the Mediterranean fruit fly (Cera titis capita ta Wied.)

Abstract

Host location by the Mediterranean fruit fly (Cerutitis cupitatu Wiedemann) was studied from the viewpoint of olfactory and optical properties of certain fruits. Oranges, tangerines, plums, lemons, strawberries and grapes were found to be significantly more attractive for mated females than for mated males of C. cupitutu ( fig. 1). When compared with mated females, virgin females were definitely less attracted to oranges and odourless orange dummies (fi . 2). Dimension has a clearcut influence on the attractiveness of natural fruits for both sexes of the Mejterranean fruit fly. The most attractive rest fruit for female and male C. capitatu (oran e) had the largest size, while the least attractive test fruit (grape) had the smallest size ( fig. 1). The refatively low attractiveness of grapes could be considerably elevated by changin their greenish-yellow colour to purple (table).Since the rate of attraction of female C. cupitutu to oranges, lemons, strawberries and to their corresponding, odourless dummies did not differ significantly ( fig. 2), it was assumed that the fruit volatiles are not essential for the location of those fruits. Moreover, removal of the funiculus and arista from both antennae of female C. cupitutu failed to su press the attraction rate of the former to dummies supplemented by orange volatiles, if comparef with the respective responses of untreated females (fig. 3). The dispensableness of olfactory cues for fruit recognition was corroborated by a similar degree of attractiveness exerted by odourless dummies and dummies impregnated with five gradually increasing dosages (from Electrophysiological recordings from olfactory sensilla on the antenna1 funiculi of female C. cupitutu revealed that the former were particularly responsive to the volatiles of orange, lemon and bergamot fruits applied in dosages increasing from lo-* to lo2 pg (receptor potentials ranging from = 0.8 to = 2.3 mV), while they were less sensitive to the volatiles of apricot (receptor potentials ranging from = 0.5 to = 1.3 mV). The receptor potentials elicited by the above essential oils in olfactory sensilla of the females were = 2.8-3.4 times higher than the receptor potentials induced in corresponding sensilla of the males (fig. 5). It follows that the essential oils of certain host fruits provide olfactory stimuli to female and less so to male C. cupitatu, in spite of the relative insignificance of the former for fruit recognition. Water, which may be emitted as vapour from the leaves and fruits of host trees, was found to induce receptor potentials of similar magnitude (ranging from = 0.3 to = 1.7 mV in response to 0.1-5.0 1. 11 of water) in the olfactory sensilla of both sexes ( fig. 6).to 10' pg) of orange volatiles ( fig. 4).

Morphological characterization of the antennal lobes in the Mediterranean fruit fly Ceratitis capitata

“…For example, electrophysiological recordings from antennae of medfly adults have shown a higher sensitivity of females than males for some Citrus peel oils and volatile compounds (Light et al 1988(Light et al , 1992Levinson et al 1990;Hernandez et al 1996), while behavioral tests revealed a stronger preference of males than females for the volatiles of orange flavedo (Katsoyannos et al 1997). In females, odor preference may be affected by mating behavior: it has been observed that females are more attracted by the male-produced pheromone than the ripe guava odor during early sexual maturity, but this preference is inverted after mating (Jang 1995).…”

Attractiveness of 79 Compounds and Mixtures to Wild <I>Ceratitis capitata</I> (Diptera: Tephritidae) in Field Trials

“…Other studies have found possible female attractants among plant, fruit, or protein hydrolysate volatiles. Many of these compounds produce electroantennogram responses from female antennae or attract C. capitata females in laboratory tests (Keiser et al 1975;Light et al 1988Light et al , 1992Jang et al 1989;Dickens et al 1990; Levinson et al 1990;Cossé et al 1995;Hernández et al 1996;Prokopy and Vargas 1996;Warthen et al 1997). However, Þeld attractiveness or effectiveness has only been investigated under varied experimental conditions for a few compounds such as (E)-6-methyl nonenoate, (E)-6-nonenol and aliphatic acids (Ohinata et al 1977), ammonia salts (Gothilf andLevin 1987, Baker et al 1990), alkyl-pyrazines and geranyl acetate (Baker et al 1990), protein hydrolysates (Gothilf and Levin 1987, Heath et al 1994, Katsoyannos and Hendrichs 1995, and ammonia compounds with methylamines and putrescine (Heath et al 1991(Heath et al , 1994(Heath et al , 1996Epsky et al 1995;Ros et al 1997;Bakri et al 1998).…”

Plant Odors as Fruit Fly Attractants

“…Total airborne volatiles from fresh oranges elicited greater response of females than males (Levinson 1990;Hernández et al 1996). Additional tests conducted in large field cages housing naturally planted orange trees showed that both sexes of C. capitata respond to chemicals released from artificial cuts made in the pulp of peeled oranges (Citrus sinensis L.) and also to natural or commercial orange juice applied to the surface of yellow 7.0 cm diameter spheres (Katsoyannos et al 1997).…”

“…EAGs or electrophysiological recordings from olfactory sensilla on the antennal funiculi of C. capitata showed that both males and females detect blends of citrus peel essential oils (Levinson 1990;Hernández et al 1996) as well as most individual compounds (Light et al 1992;Hernández et al 1996). Total airborne volatiles from fresh oranges elicited greater response of females than males (Levinson 1990;Hernández et al 1996).…”