Volatile host fruit odors as attractants for the oriental fruit fly (Diptera: Tephritidae)

We examined the responses of oriental fruit flies, Bactrocera dorsalis Hendel, to the odors of different stages and types of fruit presented on potted trees in a field cage. Females were most attracted to odors of soft, ripe fruit. Odors of common guava were more attractive to females than papaya and starfruit, and equally as attractive as strawberry guava, orange, and mango. In field tests, McPhail traps baited with mango, common guava, and orange captured equal numbers of females. Traps baited with mango were compared with 2 commercially available fruit fly traps. McPhail traps baited with mango captured more females than visual fruit-mimicking sticky traps (Ladd traps) and equal numbers of females as McPhail traps baited with protein odors. Results from this study indicate that host fruit volatiles could be used as lures for capturing oriental fruit flies in orchards.     

Flight Tunnel Responses of Diachasmimorpha longicaudata (Ashmead) (Hymenoptera: Braconidae) to Olfactory and Visual Stimuli

Cohorts of mass-reared, naive Diachasmimorpha longicaudata, parasitoids of tephritid fruit flies, were released in a laminar airflow wind tunnel to study their responses to visual and olfactory stimuli associated with their host habitat. Parasitoids were five times more likely to land on yellow plastic spheres emitting the odor of ripe, guava fruit (Psidium guajava L.) than to spheres emitting clean air. The rate of landing was not modified by the presence of green artificial leaves adjacent to the spheres in the tunnel or by the inclusion of green leaf volatiles emanating with the guava odors. However, hovering activity was twice as frequent around spheres adjacent to artificial leaves than around isolated spheres. Oviposition activity on spheres emitting guava odor was not affected by the presence of artificial leaves nor by green leaf volatiles. This suggests that inexperienced D. longicaudata may be instinctively attracted to foliage and to fruit odor but that landing (arrestment) and oviposition are influenced more by odor than by the appearance of fruit or foliage. D. longicaudata are not instinctively attracted to larvae of Bactrocera dorsalis in the absence of host-habitat stimuli. More wasp activity occurred around oviposition units containing larvae if the odor of ripe/overripe guava was present. Successful wasp reproduction occurred only in units with guava odor.     

Bactrocera dorsalis preference for and performance on two mango varieties at three stages of ripeness

Most tropical fruit flies only lay into mature fruit, but a small number can also oviposit into unripe fruit. Little is known about the link between adult oviposition preference and offspring performance in such situations. In this study, we examine the influence of different ripening stages of two mango, Mangifera indica L. (Anacardiaceae), varieties on the preference and performance of the Oriental fruit fly, Bactrocera dorsalis (Hendel) (Diptera: Tephritidae), a fly known to be able to develop in unripe fruit . A series of laboratory-based choice and no-choice oviposition experiments and larval growth trials were carried out. The results demonstrated a general preference by B. dorsalis for mango variety Oakrong over variety Namdorkmai, but in most cases the single largest dependent variable influencing results was fruit ripening stage. Ripe and fully-ripe mangoes were most preferred for oviposition by B. dorsalis . In contrast, unripe mango was infrequently used by ovipositing females, particularly in choice trials. Consistent with the results of oviposition preference, ripe and fully-ripe mangoes were also best for offspring survival, with a higher percentage of larval survival to pupation and shorter development times in comparison to unripe mango. Changes in total soluble solids and pericarp toughness correlated with changing host use across the ripening stages. Regardless of the mango variety or ripeness stage, B. dorsalis had difficulty penetrating the pericarp of all fruits offered in experiments. Larval survival was also often poor in all experiments. We discuss the possibility that there may be differences in the ability of laboratory and wild flies to penetrate fruit for oviposition, or that in the field flies more regularly utilize natural fruit wounds as oviposition sites.     

What Do Mexican Fruit Flies Learn When They Experience Fruit?

Mexican fruit flies learn fruit characteristics that enable them to distinguish familiar fruits from novel fruits. We investigated whether mature Mexican fruit flies learn fruit color, size or odor. We found no evidence that female flies learn fruit color or size after experience with host fruit, including oviposition. However, green fruit and fruit models were more attractive than yellow and red fruit and fruit models regardless of previous experience. Females with grapefruit experience were more attracted to fruit models with extract of either grapefruit peel or pulp, than to models without extract. Females with no experience with grapefruit were not attracted to models treated with grapefruit extract. These results indicate that females learned fruit odor during exposure to grapefruit.     

Role of host fruit color in the behavior of the walnut fly Rhagoletis juglandis

Observations and sticky-trap tests were used to assess the effect of fruit color on the behavior of adult male and female Rhagoletis juglandis Cresson (Diptera: Tephritidae), a tephritid that infests husks of Arizona walnut in southeastern Arizona. In the first experiment, during which flies were observed foraging among walnut models suspended from small walnut trees, models were painted green to appear ripe and uninfested or yellow with brown patches to appear ripe and infested. Flies used for this first experiment were also of two types: prior to observations, one group of flies had access to real walnuts for 1.5 days (prior experience) while the other group of flies was held without real walnut fruits (no prior experience). Regardless of prior experience with real walnut fruits, female flies landed on green models more than yellow/brown models. Experienced males also were more likely to land on green models than on yellow/brown models. More interactions also occurred on green models, because there were more landings.In the field behavioral assay, flies from a natural population given a choice of green, yellow, and yellow/brown models landed most often on green models, and all interactions and oviposition attempts occurred on green models. Flies also distinguished models by color in field sticky trap assays.These results suggest that female response to ripeness cues is innate, while males develop a preference for green based on their encounter rate with females.     

Visual and olfactory stimuli and fruit maturity affect trap captures of Oriental fruit flies (Diptera: Tephritidae)

An effective lure-and-kill trap is a potentially important instrument in monitoring and controlling oriental fruit flies, Bactrocera dorsalis (Hendel). A number of experiments were performed in an orchard of commercial guava, Psydium guajava L., to determine how fly captures are affected by combining visual and olfactory stimuli, and by the timing of trap deployment relative to host phenology. Baiting sticky Ladd traps with hydrolyzed liquid protein significantly increased the number of captured flies. Mostly male flies were caught in the absence of mature guava fruit, whereas mostly female flies were caught when ripe fruit was abundant. These results suggest that an effective oriental fruit fly trap should include both visual and olfactory lures, and that proper timing of trap deployment can be an important factor in monitoring female abundance in oriental fruit fly populations.     

Attraction of Mexican Fruit Flies (Diptera: Tephritidae) to Grapefruit: Enhancement by Mechanical Wounding of and Experience with Grapefruit

Wild strain, mated, female Mexican fruit flies, Anastrepha ludens (Loew), with no prior experience with fruit (naive), were not attracted to grapefruit, a preferred cultivated host, in wind tunnel experiments. Naive, mated laboratory strain females were attracted. Prior experience with grapefruit increased attraction of both laboratory and wild strains. More females were attracted to fruit with peel damage than to undamaged fruit, indicating that fruit odor mediated attraction. More naive than experienced females attempted to oviposit on the sides of the wind tunnel. Experienced laboratory males, but not wild males or naive males, were attracted to grapefruit. Attraction and oviposition behavior of laboratory flies was greater than that of wild flies.     

Classical Olfactory Conditioning in the Oriental Fruit Fly,Bactrocera dorsalis

The oriental fruit fly, Bactrocera dorsalis, is a serious pest of fruits and vegetables. Methyl eugenol (ME), a male attractant, is used to against this fly by mass trapping. Control effect may be influenced by learning, which could modify the olfactory response of the fly to this attractant. To collect the behavioral evidence, studies on the capability of this fly for olfactory learning are necessary. We investigated olfactory learning in male flies with a classical olfactory conditioning procedure using restrained individuals under laboratory conditions. The acquisition of the proboscis extension reflex was used as the criterion for conditioning. A high conditioned response level was found in oriental fruit flies when an odor was presented in paired association with a sucrose reward but not when the odor and sucrose were presented unpaired. We also found that the conditioning performance was influenced by the odor concentration, intertrial interval, and starvation time. A slight sensitization elicited by imbibing sucrose was observed. These results indicate that oriental fruit flies have a high capacity to form an olfactory memory as a result of classical conditioning.     

Revised irradiation doses to control melon fly, Mediterranean fruit fly, and oriental fruit fly (Diptera: Tephritidae) and a generic dose for tephritid fruit flies

Currently approved irradiation quarantine treatment doses for Bactrocera cucurbitae (Coquillet), melon fly; Ceratitis capitata (Wiedemann), Mediterranean fruit fly; and Bactrocera dorsalis (Hendel), oriental fruit fly, infesting fruits and vegetables for export from Hawaii to the continental United States are 210, 225, and 250 Gy, respectively. Irradiation studies were initiated to determine whether these doses could be reduced to lower treatment costs, minimize any adverse effects on quality, and support a proposed generic irradiation dose of 150 Gy for fruit flies. Dose-response tests were conducted with late third instars of wild and laboratory strains of the three fruit fly species, both in diet and in fruit. After x-ray irradiation treatment, data were taken on adult emergence, and adult female fecundity and fertility. Melon fly was the most tolerant of the three species to irradiation, and oriental fruit fly was more tolerant than Mediterranean fruit fly. Laboratory and wild strains of each species were equally tolerant of irradiation, and larvae were more tolerant when irradiated in fruit compared with artificial diet. An irradiation dose of 150 Gy applied to 93,666 melon fly late third instars in papayas resulted in no survival to the adult stage, indicating that this dose is sufficient to provide quarantine security. Irradiation doses of 100 and 125 Gy applied to 31,920 Mediterranean fruit fly and 55,743 oriental fruit fly late third instars, respectively, also resulted in no survival to the adult stage. Results support a proposed generic irradiation quarantine treatment dose of 150 Gy for all tephritid fruit flies.     

Apple maggot fly response to red sphere traps in relation to fly age and experience

Responses of the apple maggot fly,Rhagoletis pomonella (Walsh), to 8 cm red sticky sphere traps, baited with the synthetic fruit odor butyl hexanoate, were investigated in field-caged apple trees containing green or red Gravenstein apples. Trap capture rate and the probability of oviposition in apples before capture generally increased with female age and number of mature eggs in ovaries. Two days of pre-test exposure of mature females to red hawthorns, green Red Delicious apples or green Gravenstein apples had no significant effect on the likelihood of a fly finding a red sphere. However, before capture on a sphere or departing a tree, hawthorn-exposed females found significantly fewer apples and laid significantly fewer eggs than females exposed to Gravenstein apples. Variation in duration of pre-test exposure (1–4 days) of flies to Gravenstein apples had no detectable influence on female response to apples or to a red sphere in a test tree. The relevance of these findings to effectiveness of sphere traps, forR. pomonella control in commercial orchards is discussed.     

Oviposition Site-Selection by Bactrocera dorsalis Is Mediated through an Innate Recognition Template Tuned to γ-Octalactone

Innate recognition templates (IRTs) in insects are developed through many years of evolution. Here we investigated olfactory cues mediating oviposition behavior in the oriental fruit fly, Bactrocera dorsalis, and their role in triggering an IRT for oviposition site recognition. Behavioral assays with electrophysiologically active compounds from a preferred host, mango, revealed that one of the volatiles tested, γ-octalactone, had a powerful effect in eliciting oviposition by gravid B. dorsalis females. Electrophysiological responses were obtained and flies clearly differentiated between treated and untreated substrates over a wide range of concentrations of γ-octalactone. It triggered an innate response in flies, overriding inputs from other modalities required for oviposition site evaluation. A complex blend of mango volatiles not containing γ-octalactone elicited low levels of oviposition, whereas γ-octalactone alone elicited more oviposition response. Naïve flies with different rearing histories showed similar responses to γ-octalactone. Taken together, these results indicate that oviposition site selection in B. dorsalis is mediated through an IRT tuned to γ-octalactone. Our study provides empirical data on a cue underpinning innate behavior and may also find use in control operations against this invasive horticultural pest.     

植物果实、颜色和形状对橘小实蝇产卵选择的影响

橘小实蝇Bactrocera dorsalis(Hendel)是近几年入侵江苏南部地区,严重危害当地水果、蔬菜的重要害虫。为深入了解其在该地区果树、蔬菜上的产卵特性,进行植物果实、颜色和形状对其产卵选择影响的研究。实验室中"纸杯法"的产卵选择试验结果表明,橘小实蝇对不同水果的产卵偏好性由高到低依次为:柑橘、香蕉、芒果、枣、石榴、苹果、桃子、梨、李、葡萄、柿;对不同蔬菜的产卵偏好性由高到低依次为:丝瓜、豇豆、苦瓜、黄瓜、茄子、南瓜、青椒、番茄。对不同寄主颜色和形状的产卵选择特点为,雌虫常选择桔黄色、绿色,以及圆球形的寄主产卵,而较少选择黑色、方形的寄主产卵。从试验结果可以看出,寄主果实散发出的气味,及其颜色和形状对橘小实蝇的产卵选择有影响。     

Behavioural responses of female Queensland fruit fly, Bactrocera tryoni, to mineral oil deposits

Behavioural responses of Queensland fruit fly, Bactrocera tryoni (Froggatt) (Diptera: Tephritidae), females to fruit dipped in water and fruit dipped in 0.5% (vol/vol) aqueous emulsions of a mineral oil were determined and analysed. The mineral oil was an nC20–22 distillation fraction of the base oil used to produce an nC23 horticultural mineral oil. Females caged with oil‐treated fruit had significantly longer prelanding intervals than females caged with water‐dipped fruit. The latter was attacked immediately or shortly after being caged with flies whereas some oil‐dipped fruit was not attacked within 180 min. The percentage of landings that led to oviposition on water‐ and oil‐treated fruit were 58 and 13%, respectively, and the percentages ovipositing after probing were 74 and 25%, respectively. Likewise, average times spent probing were 7 vs. 31 s whereas average times spent ovipositing were 321 vs. 223 s. Females spent less than half as much time on oil‐treated fruit than on water‐treated fruit. Transition probabilities of rejection, when applied to the behaviour sequence indicated that oil‐treated fruits are about nine times less likely to be infested with B. tryoni.     

Olfactory responses ofTrichogramma maidis Pint,et Voeg.: Effects of chemical cues and behavioral plasticity

Oriented responses of Trichogramma maidisPint, et Voeg. to airborne odors were observed in a four-armed olfactometer. Experiments were carried out with odors of host eggs, the sex pheromone of Ostrinia nubilalisHbn, and maize extract, offered singly or in combination, both to naive wasps and to wasps previously exposed to the tested odor during an oviposition experience. The exploratory behavior in the olfactometer was quantified by means of a computer program which performed a space-time analysis of the insect 's movements. Whereas the naive wasps did not respond to the odor of the eggs, the synthetic sex pheromone of O. nubilalis,or the maize extract presented singly, they did react to a mixture of these three volatile cues. Prior oviposition in the odor of maize extract or in the combination of odors induced an increased preference toward the conditioning scent. This phenomenon did not occur when the wasps were conditioned to egg odor or sex pheromone alone. These results suggest that females can learn to associate some olfactory cues with the presence of the host. Immediately following the presentation of the combination of odors, a strong attraction of experienced wasps occurred; it decreased as the experiment progressed and finally reached the level presented by naive insects. Adult conditioning to the combination of odors also resulted in reduced variability in the behavioral responses.     

Fruit Ripening Signals and Cues in a Madagascan Dry Forest: Haptic Indicators Reliably Indicate Fruit Ripeness to Dichromatic Lemurs

Fruit ripeness can be indicated through changes in chromaticity, luminance, odor, hardness, and size to attract seed dispersing animals. We quantified these attributes for both ripe and unripe fruits of 31 lemur-dispersed plant species in Ankarafantsika National Park, a tropical dry forest in northwestern Madagascar. We used spectroscopy, gas-chromatography mass-spectrometry, and a modified force gauge to quantify chromaticity, luminance, odor, and hardness. We compared these traits between unripe and ripe fruits of each species to determine which traits reliably indicate fruit ripeness across species. Overall, ripe fruits were significantly heavier and softer than unripe fruits. Ripe fruits were not more chromatically-conspicuous or odiferous relative to unripe fruits, nor were ripe fruits more conspicuous in the luminance channel. Contrary to expectation, our findings indicate that, in this particular system, plant-lemur interactions may be strongly mediated by haptic traits, such as fruit hardness, which are consistent and reliable indicators of fruit ripeness. Despite the potential importance of haptic indicators of fruit ripeness, they are underrepresented in the literature on sensory ecology.     

Influence of Conspecific Presence, Experience, and Host Quality on Oviposition Behavior and Clutch Size Determination in Anastrepha ludens (Diptera: Tephritidae)

Females of some insect species adjust the number of ovipositions and clutch size adaptively depending on conspecific density and probably experience. In a series of three experiments, we examined the effect of the presence of conspecifics, host quality, and oviposition experience on oviposition behavior and clutch size determination by females of the polyphagous fruit fly Anastrepha ludens (Diptera: Tephritidae). In the first experiment, we determined that grouped (eight females per cage) A. ludens females tended to visit and oviposit in more hosts than did solitary females probably as a result of stimulation by the presence of conspecifics. We also determined that females with previous oviposition experience visited and oviposited in more hosts than inexperienced ones. Importantly, when females were grouped, we observed significantly more landings on unoccupied hosts (i.e., devoid of flies) than on occupied ones (i.e., with at least one fly on it). However, oviposition experience, and not female density, was the most important factor affecting clutch size. Naive females deposited larger egg clutches than experienced ones. In the second experiment, we found that oviposition experience and host quality (i.e., clean fruit or fruit covered with a host marking pheromone [HMP] extract), influenced clutch size and the decision of females to defend or not defend the host. Clutch size and number of fights were greater on clean than on HMP-marked hosts. In the third experiment, we observed that host quality (i.e., size) played a significant role with regard to the number of female fights, host marking behavior, and clutch size. Specifically, females fought and dragged their aculeus longer on small- and medium-sized hosts than on large ones. But this behavior varied according to whether females were kept alone or grouped. Clutch size was greatest in the largest hosts. Considering all the above, we believe that the observed increase in ovipositional activity by grouped A. ludens females can be attributed to competition through mutual interference and not social facilitation as has been reported in other tephritid species.     

RESPONSE TESTS OF CONE FLIES (STROBILOMYIA SPP.) TO DAHURIAN LARCH CONE VOLATILES1)

Abstract Several main monoterpenes and their combinations from Dahurian larch (Larix gmelinii Rupr.) cones were used as odor sources in olfactory experiment to test the responses of larch cone flies (Strobilomyia spp.) in 1998. The results revealed that blend of α -pinene, β -pinene, laurene and β -ocimene in a ratio close to its volatile profile of damaged cones achieved the best response while certain odors showed repellent tendency to cone flies. Field spraying Dahurian larch cones with some of its volatile components had mixed results but support the olfactory testing results. The role of monoterpenes in cone fly host location and oviposition in terms of attractive signals or repellent is discussed.     

Susceptibility of low-chill blueberry cultivars to Mediterranean fruit fly, oriental fruit fly, and melon fly (Diptera: Tephritidae)

No-choice tests were conducted to determine whether fruit of southern highbush blueberry, Vaccinium corymbosum L., hybrids are hosts for three invasive tephritid fruit flies in Hawaii. Fruit of various blueberry cultivars was exposed to gravid female flies of Bactrocera dorsalis Hendel (oriental fruit fly), Ceratitis capitata (Wiedemann) (Mediterranean fruit fly), or Bactrocera cucurbitae Coquillet (melon fly) in screen cages outdoors for 6 h and then held on sand in the laboratory for 2 wk for pupal development and adult emergence. Each of the 15 blueberry cultivars tested were infested by oriental fruit fly and Mediterranean fruit fly, confirming that these fruit flies will oviposit on blueberry fruit and that blueberry is a suitable host for fly development. However, there was significant cultivar variation in susceptibility to fruit fly infestation. For oriental fruit fly, 'Sapphire' fruit produced an average of 1.42 puparia per g, twice as high as that of the next most susceptible cultivar 'Emerald' (0.70 puparia per g). 'Legacy', 'Biloxi', and 'Spring High' were least susceptible to infestation, producing only 0.20-0.25 oriental fruit fly puparia per g of fruit. For Mediterranean fruit fly, 'Blue Crisp' produced 0.50 puparia per g of fruit, whereas 'Sharpblue' produced only 0.03 puparia per g of fruit. Blueberry was a marginal host for melon fly. This information will aid in development of pest management recommendations for blueberry cultivars as planting of low-chill cultivars expands to areas with subtropical and tropical fruit flies. Planting of fruit fly resistant cultivars may result in lower infestation levels and less crop loss.     

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.     

秋家蝇对两种卫矛植物的趋性

卫矛是常见的绿化植物,而秋家蝇Musca autumnalis De Geer是畜牧业的重要昆虫。在室内利用Y型嗅觉仪对欧洲卫矛Euonymus europaeus和胶东卫矛E. kiautschovicus气味对秋家蝇Musca autumnalis De Geer的引诱效果进行了研究。结果表明：两种植物都对秋家蝇的雌性成虫有引诱作用,而欧洲卫矛引诱效果更好。进一步对叶和花的气味进行的观察表明,卫矛吸引秋家蝇主要依靠花的气味,但叶的气味也有一定的吸引作用; 叶的气味对花的引诱效果有增效作用。利用几种试剂（水、乙醇和正己烷）对欧洲卫矛花的气味物质进行了抽提,测试结果表明水或乙醇抽提物比正己烷抽提物引诱效果更好; 冷冻花与新鲜花的引诱效果没有显著的差异。