Host deprivation influence on response of Rhagoletis pomonella to its oviposition deterring pheromone

ABSTRACT. The response of host-depibved Rhagoletis pomonella Walsh (Diptera, Tephritidae) females to host fruit ( Crataegus viridis L.) marked with R.pomonella oviposition deterring pheromone was measured in the laboratory. A positive correlation was found between length of host deprivation (5, 10, 20, 40 or 80 min) and probability of host acceptance (i.e. oviposition) by flies. The results are discussed in relation to current theories on physiological control of insect feeding and oviposition behaviour.     

Oviposition deterring pheromone in Rhagoletis cerasi: Behavioral laboratory test to measure pheromone activity

Current investigations concerning the identification of the chemical nature of the oviposition deterring pheromone of the European cherry fruit fly, Rhagoletis cerasi L., are conducted in an interdisciplinary research program by combining chemistry with behavioral evaluation. The methods used to collect and evaluate the pheromone by an improved semi-quantitative behavior test are described.

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Zusammenfassung Nach einer einleitenden Übersicht über den heutigen Stand der Erkenntnisse auf dem Gebiet der eiablage-hemmenden Pheromone (ODP) bei Fruchtfliegen und insbesondere der Kirschenfliege wird der verbesserte Verhaltenstest beschrieben, welcher für den halb-quantitativen Nachweis von ODP-Aktivität entwickelt worden ist. Im laufenden interdisziplinären Forschungsprogramm an der Eidg. Forschungsanstalt Wädenswil wird versucht, durch enge Zusammenarbeit zwischen Biologe, Chemiker und Elektrophysiologe das ODP der Kirschenfliege möglichst mit geringem Anteil an Verunreinigung einzusammeln, zu reinigen und einer chemischen Identifikation der ODP Komponenten zugänglich zu machen.Die Möglichkeiten und Grenzen des Verhaltenstests werden diskutiert und die Empfindlichkeit des Verfahrens mittels einer Konzentrationsreihe von Pheromonextrakt aufgezeigt.

     

Oviposition deterring pheromone in Rhagoletis cerasi: Biological activity of a pure single compound verified in semi-field test

A pure single compound, a palmityl-glucopyranoside identified as component of the oviposition deterring pheromone (ODP) of the European cherry fruit fly was evaluated with respect to its biological activity by means of a semi-field bioassay in a large field-cage with host plants. The comparison of the observed behaviors of flies exposed to clean cherries, to cherries treated with a standard ODP solution and with the pure compound revealed that palmityl-glucopyranoside elicited the same response as did the crude ODP solution. Irritation indices are described that seem to be of use for the characterization of cherry fruit fly behavior in the presence and absence of ODP. The advantages of the field-cage test over the standard laboratory tests are discussed.

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Zusammenfassung Mit zunehmenden Reinigungsschritten am Rohextrakt des Markierungspheromones (ODP) der Kirschenfliege, Rhagoletis cerasi L., und zunehmenden Reinheitsgrad des aktiven Prinzipes nimmt die Menge an Substanz ab, welche sowohl für die chemische Analyse wie auch die Prüfung der biologischen Aktivität zur Verfügung steht. Beim Vorliegen einer nicht mehr wägbaren Menge eines reinen Stoffes im Sommer 1985, welcher als ein Palmityl-glucopyranosid identifiziert werden konnte (Hurter et al., 1987), musste deshalb auf den üblichen Verhaltenstest im Labor verzichtet und ein neuer Lösungsansatz gefunden werden. Nachdem ein erster elektrophysiologischer Test positive Resultate gezeight hatte, wurde die Fraktion Nr. 2634 in einem grossen Freilandkäfig mit Kirschenpflanzen und natürlichen Früchten in einem Verhaltenstest auf ihre biologische Wirksamkeit geprüft.Die in dieser Arbeit präsentierten Resultate zeigen nicht nur, dass mit dem Palmityl-glucopyranosid eine ähnliche Wirkung erzielt wurde wie mit natürlichen ODP, sondern zum erstenmal konnte demonstriert werden, dass in R. cerasi und möglicherweise in andern Fruchtfliegenarten eine einzelne chemische Substanz eine eiablagehemmende Wirkung ausüben kann.

     

Realized heritability of behavioral responsiveness to an oviposition deterring pheromone in the azuki bean weevil Callosobruchus chinensis

Artificial selection was conducted to reduce the behavioral responsiveness of female bruchid beetles, Callosobruchus chinensis, to the oviposition deterring pheromone excreted by conspecific females. Significant responses to selection were observed after two generations of selection. Realized heritability was estimated as 0.052 ± 0.017 from cumulative responses regressed on cumulative selection differentials. These results indicate that this pheromone communication system has significant additive genetic variance needed for its evolution.     

Male Diachasma alloeum parasitoids from two host species of tephritid fruit flies respond equally to female-produced sex pheromone

Abstract.  Diachasma alloeum is a braconid wasp that parasitizes hawthorn-infesting Rhagoletis pomonella and blueberry-infesting Rhagoletis mendax , both tephritid fruit fly sibling species. The behavioural responses of male D. alloeum originating from both fruit fly host species to hexane extracts of conspecific females originating from both host species and females of various mating status are investigated in a laboratory Y-tube olfactometer. Male D. alloeum originating from either R. mendax or R. pomonella respond to one whole-body, female equivalent hexane extract in equal frequency as to a live, virgin female; this response is at least 7.5-fold greater than to solvent controls. Male D. alloeum originating from R. mendax or R. pomonella are attracted to hexane extracts of female D. alloeum abdomens but not to extracts of the head and thorax regions. Virgin D. alloeum females attract significantly more male D. alloeum originating from either host species compared with mated females of the same age. Copulation behaviour between same host and mixed host pairs appears to be identical. Male D. alloeum are equally responsive to the female-produced sex pheromone of female D. alloeum , irrespective of females' host-species origin, suggesting that these host-specific populations can potentially interbreed.     

Prior experience affects the visual ability ofRhagoletis pomonella flies (Diptera: Tephritidae) to find host fruit

Females of the apple maggot fly,Rhagoletis pomonella, were allowed for 3 days to alight upon and oviposit in green or red 18- to 20-mm hawthorn host fruit (Crategus mollis) or green or red 45- to 55-mm apple host fruit (Malus pumila) hung from branches of potted host trees in field enclosures. Subsequently, when females were released individually on potted host trees harboring fruit of one of these types, their ability to find fruit of unfamiliar size proved unaffected by prior experience with fruit but their ability to find fruit of unfamiliar color was significantly affected. Specifically, females exposed to red hawthorns or red apples were less able to find green hawthorns or green apples than were females experienced with either of the latter fruit types. Fruit odor was found to have no effect on female ability to find familiar compared with unfamiliar green fruit. In contrast, a difference in size (or surface chemistry) between familiar and unfamiliar fruit but not a difference in fruit color had a significant negative influence on the propensity of alighting females to bore into unfamiliar fruit. Three bouts of experience with alighting upon and ovipositing into fruit over a period of about 1 h had no detectable effect on female ability to find unfamiliar fruit but did reduce propensity to bore into unfamiliar fruit. Our findings are discussed in relation to insect ability to learn visual and chemical stimuli of resources and insect propensity to form host races. We also discuss the potential impact of our findings on nonpesticidal, behavioral methods of managingR. pomonella in commercial apple orchards.     

Learning of apple fruit biotypes by apple maggot flies

Previously, we showed that after a female apple maggot fly, Rhagoletis pomonella,arrives on a host hawthorn or apple fruit, its propensity to accept (bore into) or reject that fruit prior to egg deposition can be modified by previous ovipositional experience with one or the other species and, hence, involves learning. Here, we present both field and laboratory evidence indicating that females also are able to learn characteristics of three different apple biotypes or cultivars: Early Macintosh, Red Delicious, and Golden Delicious. We suspect that females learn to discriminate among these three cultivars on the basis of differences in chemical stimuli among cultivars. The effect of fruit cultivar learning was not as strong as the effect of fruit species learning.     

Effects of recent experience on foraging in tephritid fruit flies

In field-cage studies, we investigated how the foraging behavior of tephritid fruit flies is modified by experience immediately prior to release on host plants. We observed females of a relatively monophagous species,Rhagoletis mendax (blueberry maggot fly), an oligophagous species,Rhagoletis pomomella (apple maggot fly), and a polyphagous species,Ceratitis capitata (Mediterranean fruit fly). Just prior to release on a host plant, the following kinds of stimuli were supplied: (1) single oviposition in a host fruit, (2) contact with 20% sucrose, (3) contact with a mixture of protein food (bird feces and sucrose), (4) contact with water, and (5) a walk over a host-plant leaf. When flies foraged on host plants without resources, search was most intensive (as measured by number of leaves visited) following a single oviposition in fruit, but residence time generally was the same following exposure to sugar, protein, and fruit stimuli.Rhagoletis mendax andC. capitata females visited the fewest leaves following exposure to water or host leaves, whereasR. pomonella foraged equally intensively following exposure to food stimuli, water, or leaves. On host plants containing resources (fruit and protein food), a single oviposition dramatically increased the number of females of all three species that found fruit compared to females that received experience with food, water or foliar stimuli. We found no significant effect of recent brief experience with any of the stimuli on subsequent attraction to protein food. Overall,C. capitata exhibited a higher propensity to abandon host plants than eitherR. mendax orR. pomonella. We suggest that this may reflect adaptations to differences in distribution of host plants in nature, strategies of dispersal, and host range.     

Morphological and electrophysiological mapping of tarsal chemoreceptors of oviposition-deterring pheromone in Rhagoletis pomonella flies

Light microscopy and S.E.M. observations revealed that Rhagoletis pomonella female tarsi, bearing the principal receptors of oviposition-deterring fruit marking pheromone (ODP), have 3 types of chemosensilla: B, C and D. Using electrophysiological hair tip-recording techniques, we found that D chemosensilla located in pairs on distal ventrolateral portions of the 2nd, 3rd and 4th tarsomeres of each leg were highly sensitive to stimulation by the pheromone. D chemosensilla located in pairs on the 5th tarsomere of each leg were moderately sensitive to the pheromone, while the B and C chemosensilla of all tarsi were nearly or completely insensitive to it. For reasons discussed, the D chemosensilla on the prothoracic tarsi may be the most important in providing sensory input eliciting oviposition deterrence.     

Learning to find fruit in Ceratitis capitata flies

Wild Mediterranean fruit fly females, Ceratitis capitata (Wiedemann), from an essentially monophagous population on the island of Hawaii were exposed to natural mock orange (Murraya paniculata) or sweet orange (Citrus sinensis) host fruit hung from branches of potted trees for 3-day periods in field enclosures. Subsequently, when flies were released individually onto potted trees harboring one or the other (or a mixture) of these fruit types, a higher proportion visited the type of fruit with which they were familiar (and visitors found familiar fruit faster) compared with the fruit type with which they were unfamiliar. Moreover, fruit-finding flies of this monophagous population attempted oviposition exclusively in the familiar fruit type, and thus appeared to be just as capable of learning to accept fruit for oviposition as wild flies from a previously-tested polyphagous population on the island of Maui. Additional tests were conducted in which flies were exposed to natural or colored-wax-covered mock oranges or sweet oranges and tested for response to colored-wax-covered natural or artificial fruit. Results suggested that fruit size was the principal character learned and used in finding mock orange or sweet orange fruit, while fruit color and odor appeared to be of little or no importance in this regard.

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Résumé Des femelles sauvages d'une population essentiellement monophage de C. capitata Wiedemann, provenant de l'île de Hawaï, ont été mises en présence pendant des périodes de 3 jours dans des enceintes dans la nature à des fruits de Murraya paniculata et de Citrus sinensis suspendus à des branches d'arbres empotés. Quand les mouches ont été libérées individuellement sur les arbres empotés portant l'un ou l'autre de ces fruits (ou leur mélange), une plus forte proportion a visité le fruit avec lequel elles étaient familiarisées (et l'ont trouvé plus vite) que le fruit avec lequel elles ne n'étaient pas. De plus, les femelles découvrant des fruits de cette population monophage ne tentèrent de pondre que dans le type de fruit avec lequel elle étaient familiarisées. Elles se montrèrent aussi capables que les mouches d'une population polyphage de l'île de Maui d'apprendre à accepter de nouveaux fruits pour pondre. Des expériences complémentaires ont été réalisées dans lesquelles les mouches étaient mises en présence de fruits de M. paniculata ou de C. sinensis naturels ou couverts de cire colorée ou encore de fruits artificiels. Les résultats suggèrent que la taille du fruit est le principal critère d'apprentissage utilisé pour trouver M. paniculata ou C. sinensis, la couleur et l'odeur du fruit étant apparus comme de moindre importance ou sans effet.

     

The effect of an oviposition deterring pheromone on egglaying in Pieris brassicae

A laboratory study was conducted in order to determine the influence of the oviposition deterring pheromone (ODP) upon the distribution of eggbatches and eggs by Pieris brassicae females. This pheromone is known to be associated with eggs. Butterflies were offered a choice between cabbage leaves treated in various ways with the ODP and control leaves. The presence of intact conspecific eggs on the treated leaf appeared to have a moderate deterrent effect upon oviposition. An aqueous solution of the ODP, obtained by washing eggs in distilled water was found to have a somewhat higher deterrent effect. Most effective in deterrence of oviposition, however, appeared to be a washing of P. brassicae eggs in methanol. Such a methanol solution can be stored at low temperatures for at least three years without loosing activity. Application of eggwash to either the upper or lower surface of the leaf does not make any difference to females. Percentage deterrence was found to increase with the concentration of eggwash. At very low concentrations no significant difference could be observed anymore in the numbers of eggbatches and eggs laid on control and treated leaf. On the other hand, even very high concentrations of methanol eggwash do not fully protect cabbage leaves against oviposition. Washing P. brassicae eggs seven times consecutively in methanol, a series of pheromone solutions is obtained, all of them were found to possess a high deterrent activity. Although percentage deterrence slowly decreases in subsequent washings, the seventh eggwash sprayed onto cabbage leaves still resulted in less than one quarter of the total number of eggbatches and eggs being laid on the treated leaf.

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Résumé Des expériences de laboratoire ont été réalisées pour déterminer d'influence d'une phéromone dissuasive de la ponte (ODP) sur la distribution des ooplaques et des oeufs de Pieris brassicae. Cette phéromone est connue comme associée aux oeufs. Les papillons ont eu le choix entre des feuilles de chou traitées de différentes façons avec ODP et des feuilles témoins. La présence d'oeufs intacts de la même espèce sur les feuilles a un effet dissuasif modéré sur la ponte. Une solution aqueuse d'ODP, obtenue par lavage des oeufs à l'eau distillée est quelque peu dissuasive. Le lavage des oeufs de P. brassicae au méthanol est apparu comme le plus dissuasif. Une telle solution au méthanol peut être stockée à basse température au moins 3 ans sans perte de son pouvoir. Les applications de l'eau de rinçage sur les faces supérieures ou inférieures des feuilles induisent le même comportement des femelles. L'effet dissuasif augmente avec la concentration de l'eau de rinçage; aux très faibles concentrations, aucune différence significative n'a pu être observée avec les témoins quant au nombre d'ooplaques et d'oeufs. Par ailleurs, même aux très hautes concentrations du méthanol, l'eau de rinçage n'inhibe pas totalement la ponte sur les feuilles de chou. En lavant 7 fois consécutives les oeufs de P. brassicae dans le méthanol, on obtient une série de solutions de phéromones, dont chacune possède un fort pouvoir dissuasif. Bien que l'effet dissuasif diminue lentement avec des rinçages successifs, la pulvérisation du septième rinçage sur les feuilles de chou réduit encore à moins du quart le nombre total d'ooplaques et des oeufs pondus sur la feuille traitée.

     

The cost of reproduction in rosehip flies,Rhagoletis basiola: Eggs are time

Summary The hypothesis was tested that egg-laying by rosehip fruit flies,Rhagoletis basiola, would lead to reduced adult survivorship compared with oviposition-deprived flies, through experimental manipulation. Oviposition-deprived flies were assigned to two groups: mated and spinster. All three treatment groups were permitted to spend equal time and energy exploring and handling hosts but only the former group were allowed to deposit eggs (three/day). Results clearly showed that ovipositing flies suffered significantly higher mortality rates and that mated and spinster flies produced similar survivorship patterns. I consider these results both as a foraging problem (i.e. laying eggs in inferior hosts can cost both eggs and life) and as a more general life history problem.     

Attractiveness of various colours to Australian tephritid fruit flies in the field

The response of tephritid fruit flies to variously coloured sticky traps was studied in the field in southeastern Queensland over three seasons (1978–81). Three species, Dacus tryoni (Froggatt), D. neohumeralis Hardy and D. cacuminatus (Hering), made up the majority of the flies captured. On a per unit area basis, a sticky flat trap was more efficient than a sticky wing trap and was adopted as the trap design. Daylight fluorescent (DF) Saturn Yellow captured significantly more flies than any of the other ten colours, or perspex and aluminium foil, tested, although the DF colours Lime, Blaze Orange and Emerald were also attractive. There was a significant correlation between the number of flies captured by a colour and the difference, in nanometres, between the peak reflected wavelength of the colour and 550 nm which is quoted as the peak wavelength reflected by green leaves. The three species did not differ in their responses to the coloured traps, and more males than females were captured. When either cuelure or methyl eugenol was added to the sticky traps no one colour emerged as significantly superior, but the yellow, and yellow/green DF colours consistently caught more flies. The attractiveness of coloured traps declined as the number of flies captured increased. The efficiency of Steiner and McPhail traps was not increased by the addition of any attractive colour. Of various possible trap shapes of equivalent surface area, circular and square traps captured more flies than did triangular, rectangular and diamond shaped traps. When spheres were tested, those of 10 cm diameter captured more flies than those of 5 cm diameter, and more flies were caught on black, than on yellow or green spheres.

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Résumé Plusieurs espèces de téphritidées, principalement Dacus tryoni, D. neohumeralis et D. cacuminatus, ont été capturées avec des pièges gluants colorés dans le S.E. Queensland (Australie) pendant 3 saisons (1978–81). Des pièges plats de 15×20 cm ont capturé plus de mouches/cm² que des pièges ailés formés par 2 plans à 90°. Les couleurs jaune-vert ont été préferées par les 3 espèces, le jaune saturne lumière du jour fluorescent ayant été le plus attractif. Une corrélation significative a été trouvée entre le nombre de mouches capturées par une couleur et la différence en nanomètres entre le mode des longueurs d'onde reflétées par cette couleur et 550 nm considéré généralement comme le mode des longueurs d'onde reflétées par les feuilles vertes. Les 3 espèces ont montré les mêmes réponses aux pièges colorés et le nombre de mâles avait tendance à excéder celui des femelles. Quand de la cuelure ou du méthyl eugénol étaient ajoutés aux pièges gluants, aucune couleur n'était significativement supérieure, mais les couleurs fluorescentes lumière du jour jaune et jaune-vert ont capturé nettement plus de mouches que le bleu, l'orange, le rouge, le noir, le blanc, la feuille d'aluminium ou le perspex clair. Le taux de capture diminuait plus le nombre de mouches sur le piège augmentait. Ceci peut expliquer la diminution apparente de la discrimination entre les couleurs quand des leurres mâles sont posés sur les pièges. Des expériences avec des pièges tachetés et un retrait quotidien des mouches ont montré que la diminution d'attractivité était une réponse à un stimulus visuel. Après plusieurs jours d'exposition, un piège de couleur relativement peu attractive, capturant des mouches à un taux faible mais appréciable, a capturé un nombre de mouches voisin de celui d'un piège de couleur attractive qui avait commencé par capturer un grand nombre de mouches, mais avait vu baisser son attractivité par suite de la présence des mouches captives. Les données hebdomadaires sur les captures n'ont pas présenté de différences suivant les couleurs, mais la sommation des captures quotidiennes (avec retrait quotidien des mouches) sur la même période a montré des différences d'attractivité significatives.Les pièges de Steiner et de McPhail n'ont présenté aucun taux de capture différent quand ils étaient peints sur les 2/3 inférieurs avec des couleurs attractives jaune-vert.Des sphères noires ont capturé plus de mouches que des sphères rouges, jaunes ou vertes, et des sphères de 10 cm de diamètre étaient plus attractives que celles de 5 cm.Quand un choix de pièges plats de la même couleur et de la même surface mais de formes diverses a été proposé aux mouches, les pièges circulaires et carrés ont capturé plus de mouches que les pièges triangulaires, rectangulaires ou rhombiques.

     

Dacus dorsalis flies can learn to find and accept host fruit

Mature oriental fruit fly females, Dacus dorsalis, from a population cultured on host fruit in the laboratory for one generation responded positively to visual and olfactory stimuli of individual natural kumquat (Fortunella japonica) and apple (Malus pumila) host fruit or models of these fruit hung from branches of potted trees in field enclosures. When females were exposed for 3 days to natural kumquats or apples on trees and subsequently released individually onto trees harboring one or the other of these fruit types, a significantly greater proportion of those exposed to kumquats than those exposed to apples or those not exposed to any fruit visited kumquats. Females exposed to kimquats for at least 3 days followed by at least 3 days of exposure to apples retained ability to find kumquats. Compared with females exposed to apples for 3 days or with naive females, females exposed to kumquats for 3 days exhibitied no less ability to find apples but did significantly refrain from accepting apples for oviposition. A final test was conducted in which females were exposed to natural kumquats or apples for 3 days and tested for response to inanimate models of either the same color and size as natural kumquats (orange, 20-mm diameter) or apples (green, 75-mm diameter) or models of the same color but opposite size. Results suggest that fruit size is the principal character learned and used in finding kumquats, which apparently are somewhat inconspicuous to an inexperienced foraging D. dorsalisfemale.     

Host marking pheromone of Rhagoletis cerasi: field deployment of synthetic pheromone as a novel cherry fruit fly management strategy

We tested the efficacy of synthetic host marking pheromone (HMP) of the European cherry fruit fly (R. cerasi) as a fruit-infestation-reducing-agent in an experimental cherry orchard. Two different pheromone deployment strategies were compared: covering entire tree canopies with synthetic HMP or treating only one half (top to bottom or lower half) of the tree canopy. Pheromone application caused a tenfold reduction in fruit infestation if the entire tree canopy was covered (0.226 vs 0.021 pupae/fruit in untreated and treated trees, respectively). Results show, nevertheless, that a significant reduction in fruit infestation can be achieved by treating only one half of tree canopies (top to bottom) (0.021 vs 0.048 pupae/fruit when comparing totally vs partially treated trees). We conclude that synthetic cherry fruit fly HMP has potential as a fruit fly management tool, especially in cases where organically grown fruit reaches high market values.     

Relative air humidity influences the function of the tarsal chemoreceptor cells of the cherry fruit fly (Rhagoletis cerasi)

ABSTRACT. Electrophysiological recordings from the tarsal D-sensilla of mature, 5–7-day-old female European cherry fruit fly ( Rhagoletis cerasi L.) revealed that a large proportion of sensilla showed no sensory activity in response to stimulation with the oviposition deterring pheromone ('ODP') or sucrose. In contrast, good recordings were obtained from almost all sensilla in freshly emerged, 1-day-old flies. Ageing, nutritional state and contamination were excluded as possible major factors influencing the responsiveness of the D-sensilla. The study of the variability in responsiveness of the sensilla of 1-day-old flies among different tarsomers, among tarsi of the same individual and among individuals, revealed that the major source of variability was among individuals.
Individual flies were also affected by the humidity in the holding cages: relative air humidity of less then 75% for 4–6 days was shown to reduce the number of D-sensilla giving recordings with a good signal-to-noise ratio. The D-sensilla on the most distal tarsomers were affected most by the reduced (30–55% r. h.) air humidity. Flies which had contact with plant leaves showed less reduction in responsiveness at low air humidity (40% r. h.) then flies without leaf contact.     

Intra-tree foraging behavior of Ceratitis capitata flies in relation to host fruit density and quality

We examined the intra-tree foraging behavior of individually-released, wild-population Mediterranean fruit flies (medflies), Ceratitis capitata (Wiedemann), on field-caged host trees bearing each of three different densities (0, 3, or 12 per tree) of non-infested host fruit (kumquat) or each of two levels of fruit quality (12 non-infested fruit or 12 fruit infested with eggs and covered with host marking pheromone). With increasing density of non-infested fruit, medflies tended to remain longer in trees, visit more fruit before leaving, oviposit more often, accept a proportionately smaller number of fruit visited, and emigrate sooner after the last egg was laid (i.e. have a shorter Giving-Up-Time). Medflies spent much less time, oviposited much less often, and exhibited a longer Giving-Up-Time on trees harboring pheromone-marked fruit than non-infested fruit. Variation in temperature within the range at which experiments were conducted (25–36°C) had little detectable influence on foraging behavior. We compare our findings with published findings on the intra-tree foraging behavior of another tephritid fly, Rhagoletis pomonella (Walsh), and with current foraging behavior theory. We discuss implications of our findings with respect to medfly management strategies, particularly fruit stripping in eradication programs and use of synthetic marking pheromone for control.

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Résumé Nous avons étudié le comportement de prospection dans un arbre, de femelles d'une population sauvage de C. capitata, libérées individuellement à l'intérieur de cages contenant des Eriobotrya japonica (kumquat), portant chacun 3 densités différentes de fruits no contaminés (0, 3, 12 par arbre) et chacun 2 niveaux de qualité de fruits: 12 fruits non infestés ou 12 fruits contaminés par des oeufs et recouverts de phéromone de marquage de l'hôte. C. capitata avait terndance à rester plus longtemps dans les arbres, à visiter plus de fruits avant le quitter, à pondre plus souvent, à accepter proportionnellement un nombre plus réduit de fruits déjà visités, à émigrer plus tôt après la ponte du dernier oeuf (c'est-à-dire à présenter un temps d'abandon plus bref), quand la densité des fruits non contaminés augmentait. C. capitata a dépensé beaucoup moins de temps, pondu beaucoup moins souvent, et présenté un temps d'abandon plus long sur les arbres portant des fruits marqués par la phéromone que sur ceux ayant des fruits non contaminés. Les variations de température dans la gamme de cells où les observations ont eu lieu (23–36°C) n'ont eu qu'une faible influence décelable sur le comportement de prospection. Nous avons comparé nos résultats avec ceux publiés sur la prospection à l'intérieur de l'arbre par une autre téphritide (Rhagoletis pomonella) et avec la théorie dominante sur le comportement de prospection. Nous discutons les conséquences de nos résultats sur les stratégies de lutte contre C. capitata, en particulier l'élimination des fruits dans les plans d'erradication et l'utilisation de phéromone synthétique de marquage.

     

Attracticidal spheres for controlling apple maggot flies: commercial-orchard trials

Wooden pesticide-treated red spheres and biodegradable sugar/flour pesticide-treated red spheres were compared with wooden sticky-coated red spheres and insecticide sprays for controlling apple maggot flies, Rhagoletis pomonella(Walsh) (Diptera: Tephritidae), in small blocks of apple trees in Massachusetts commercial orchards in 1997, 1998 and 1999. Pesticide-treated spheres received a coating of 70% latex paint, 20% feeding stimulant (sucrose), and 10% formulated insecticide (containing 20% imidacloprid). To replenish sucrose lost during rainfall, wooden spheres were capped with a disc comprised of hardened sucrose that seeped onto the sphere surface, whereas the surface of sugar/flour spheres received sucrose that seeped from the interior. Each year, each of the 24 perimeter trees of each non-sprayed block received a sphere baited with butyl hexanoate (an attractive component of host fruit odor), with the intent of intercepting immigrating flies. Based on captures of flies on unbaited sticky-coated red spheres placed near the center of each block and on periodic samples of fruit for injury, there was a consistent pattern of treatment performance. Each year, sticky-coated spheres were only slightly less effective than two or three sprays of organophosphate insecticide, sugar/flour pesticide-treated spheres were only slightly less effective than sticky spheres, and wooden pesticide-treated spheres were least effective. Versions of pesticide-treated spheres used in 1999 were more durable than those used in previous years, but further improvement is needed before either wooden or sugar/flour pesticide-treated spheres can be recommended for grower use.     

Use of fruit wounds in oviposition by Mediterranean fruit flies

Casual observations suggested that female Mediterranean fruit flies (Ceratitis capitata Wiedemann) exploit fruit wounds (including pre-existing oviposition punctures) as oviposition sites. This behaviour was quantified under field conditions in a citrus grove on the Greek island of Chios. Fruit wounds influenced oviposition behaviour in three ways. First, females were more likely to land on oranges (Citrus sinensis) that were artificially wounded than into unwounded control oranges. Second, having landed, females were more likely to attempt oviposition into a wounded orange than into control oranges. Third, females that attempted oviposition into wounded oranges usually did so directly into or very near the wound. The diameter and depth of the wound significantly influenced the tendency for female flies to land on a fruit but not their propensity, having landed, to attempt oviposition in or near the wound. The significance of this behavior in nature and implications for management of the Mediterranean fruit fly are discussed.

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Résumé Des observations fortuites nous ont suggéré que C. capitata Weidemann utilise les blessures des fruits, y compris d'anciennes piqûres de ponte, pour déposer ses oeufs. Ce comportement a été quantifié dans une orangeraie de l'île grecque de Chios. Les blessures des fruits influent sur la ponte de 3 façons. D'abord, les femelles atterissent plus fréquemment sur les oranges, Citrus sinensis, artificiellement blessées que sur les fruits intacts. Ensuite, après atterrissage, les femelles tentent plus souvent de pondre sur une orange blessée que sur des oranges intactes. Enfin, les femelles pondent directement dans la blessure ou à proximité. Le diamètre et la profondeur de la blessure influent sur la tendance à l'atterrissage, mais non sur les tentatives de ponte dans la blessure ou près d'elle. La signification de ce comportement dans la nature et ses conséquences sur la lutte contre C. capitata sont discutées.

     

Host-marking pheromone and use of previously established oviposition sites by the mediterranean fruit fly (Diptera: Tephritidae)

Under controlled conditions, the Mediterranean fruit fly, Ceratitis capitata(Wiedemann) preferred to initiate oviposition into preexisting, naturally formed oviposition punctures in a host fruit, kumquat (Fortunella japonica),over establishing new sites on the fruit. This preference was expressed despite the presence of naturally deposited host-marking pheromone (HMP)shown previously to deter oviposition. An almost-identical preference for existing punctures was expressed when females were presented with fruit bearing artificially made punctures on which HMP had been naturally deposited. Using artificial punctures and HMP extracts, the occurrence of punctures was manipulated independently of the presence of HMP.Under field-cage conditions, we found that (1) punctures stimulated egg-laying on kumquats, regardless of HMP treatment; (2) HMP extract inhibited egg-laying, regardless of the occurrence of punctures; and (3) the extent to which HMP inhibited egg-laying was greater on fruit free of punctures than on fruit bearing them. The physiological, evolutionary, and pest management implications of these results are discussed.