Female Oriental Fruit Flies Research Articles

Oviposition by the oriental fruit fly, Bactrocera dorsalis (Hendel) (Diptera: Tephritidae), on five citrus types in a laboratory

AbstractFrugivorous insects use visual, chemical and tactile cues to find a suitable host for oviposition. However, these cues can vary greatly among fruit cultivars and condition, changing their susceptibility to fruit fly oviposition. The aims of this study were to (1) determine the effects of ripeness stage and damage on oviposition propensity by sexually mature, mated female oriental fruit flies, Bactrocera dorsalis (Hendel) (Diptera: Tephritidae), on five citrus types (species and cultivars) under choice and no‐choice conditions and (2) describe the oviposition behaviour of B. dorsalis on ripe fruit of the same five citrus types that were either damaged or undamaged under no‐choice conditions. All tests were conducted in the laboratory. The citrus types tested were Citrus sinensis (L.) Osbeck cv Delta Valencia orange, Citrus sinensis (L.) Osbeck cv Glen Ora Late navel orange, Citrus limon (L) (Burm.f.) cv Eureka lemon, Citrus paradisi (Macfad.) cv Star Ruby grapefruit and Citrus reticulata (Blanco) cv Nadorcott mandarin. Peel physical properties and essential oil composition were determined for each citrus type and stage. Oviposition propensity of B. dorsalis was significantly greater on damaged citrus but was not correlated with fruit diameter, peel thickness, oil gland density or oil gland size. A total of 45 aromatic compounds were found to be significant between the five cultivars investigated, and 6 of 11 compounds were significantly associated with over‐ripe fruits. Bactrocera dorsalis spent a significantly greater proportion of time ovipositing in damaged citrus and showed higher aggression when oviposition occurred in undamaged citrus. These results suggest that the removal of damaged and fallen fruit is important for controlling this pest in citrus orchards.

Potential of Fruit Extracts as Attractants of Female Oriental Fruit Flies.

<b>Background and Objective:</b> The oriental fruit fly <i>Bactrocera dorsalis</i> (Hendel) is one of the most important insect pest species of fruit and vegetable crops in the tropical and subtropical regions. This study aimed to determine the attraction of female and male <i>B. dorsalis</i> fruit flies to the aroma of fruit juice from the host plants as well as their attraction to methanol extract, ethyl acetate extract and distillate water of selected host fruits. <b>Materials and Methods:</b> The attractiveness of the juice and extract/distillate water of the host fruits to <i>B. dorsalis</i> fruit flies was carried out in an experimental cage measuring 200×200×200 cm that was placed in the laboratory. The volatile compounds in the juice, methanol extract, ethyl acetate extract and distillate water of the selected fruits were analyzed using GCMS-Pyrolysis. <b>Results:</b> The results show that among the eight fruit juice aromas tested, the ones that significantly affected the number of trapped female <i>B. dorsalis</i> were the aromas of banana juice, papaya juice and chilli juice. The results of the analysis by GCMS-Pyrolysis showed that the methanol extract of banana fruit contains one volatile compound that was previously reported to have the ability to attract female <i>B. dorsalis</i> fruit flies. Two volatile compounds in the banana distillate water were also reported to have the ability to attract female <i>B. dorsalis</i> and other fruit flies. <b>Conclusion:</b> From the results of this study, it can be concluded that the methanol extract and distillate water of the green <i>Ambon lumut</i> banana fruit of <i>Musa acuminata</i> Colla has the potential to be developed as an attractant of female <i>B. dorsalis</i>.

The potency of minerals to reduce oriental fruit fly infestation in chili fruits.

IntroductionsIn many areas, particularly in Asia, the oriental fruit fly Bactrocera dorsalis (Hendel) causes considerable fruit damage on various plants. The fruit fly causes significant economic losses every year due to reduced fruit quantity and quality as well as export restrictions. This study aimed to examine the potency of minerals in controlling the oriental fruit fly infestation in chili fruits.MethodsExperiments were conducted under laboratory and semi-field conditions using randomized block design. Ten minerals (i.e. kaolin, talc, zinc oxide, bentonite, sulfur, dolomite, calcium oxide, calcium hydroxide, calcium carbonate, and zeolite) and an untreated control were tested under laboratory conditions. Twenty chili fruits at a green stage were soaked in each mineral suspension (2%, w/v), air-dried, and placed in a trial cage (23-L plastic container) containing 20 female oriental fruit flies. In a semi-field bioassay using a screen cage (100 cm × 70 cm × 120 cm), 20 female oriental fruit flies were exposed to a fruit-bearing chili plant sprayed with mineral suspension.ResultsTalc and calcium oxide significantly reduced the numbers of visiting fruit flies, oviposition holes, and eggs laid, as well as the percentage of infested chili fruits in a laboratory bioassay. Calcium hydroxide was substantially better than talc in controlling fruit fly infestation in a semi-field bioassay, although it was not significantly different from calcium oxide and calcium carbonate.ConclusionOverall, calcium oxide is a viable option for the long-term control of the oriental fruit fly on chili fruits. Calcium oxide could be utilized as the push component of a push-pull strategy to manage oriental fruit fly infestation in chili fruits because of its potential to inhibit the number of visiting fruit flies and oviposition.

Is the Natural Instinct to Oviposit in Mated Female Oriental Fruit Fly, Bactrocera dorsalis More of a Brain-Independent Act?

What physiological and neuro-molecular changes control the female oviposition behavior post-mating in insects? The molecular changes that occur in a gravid female insect are difficult to dissect out considering the distinct behavioral patterns displayed by different insect groups. To understand the role of the brain center in Oriental fruit fly, Bactrocera dorsalis oviposition, egg-laying behavior was analyzed in γ-octalactone exposed, decapitated mated B. dorsalis females. Interestingly, the females displayed a possible urge to oviposit, which suggests a natural instinct to pass on the gene pool. Expression analysis of certain genes involved in oviposition behavior was also carried out in these insects to explore the molecular aspects of such behavior. This study tries to assess the involvement of brain center in egg-laying and also explore the role of certain neurotransmitter-related receptors in decapitated B. dorsalis oviposition behavior. Our results indicate that B. dorsalis oviposition behavior could potentially have a bypass route of neuronal control devoid of the brain. The study reported here establishes that decapitation in gravid females fails to abolish their ability to sense ovipositional cues and also to oviposit.

Polyandry in the Fruit Fly Bactrocera dorsalis Hendel (Diptera: Tephritidae)

The Oriental fruit fly, Bactrocera dorsalis (Hendel) is a global pest of a wide variety fruits. Due to its importance, the sterile insect technique (SIT) has raised attention as a safe and sustainable solution to this pest. Successful SIT programs require a comprehensive understanding on the mating behavior of this species. Females of oriental fruit flies are known monandrous which implies that females only mate once with one male. This experiment aimed to confirm that female flies were able to mate more than once with the same (multiple mating) or different males (polyandry) in certain period of time. Four different experiments were conducted to test the hypothesis: receptivity a female to the same male (1) and different males (2) in a cage for 11 days; receptivity a mated female with the same male (3) and different males (4) in a cage for 14 days after the first mating. Results indicated that a part of the female oriental fruit flies was capable to mating more than once with the same or different males.

Visual assessment of morphological changes in female reproductive system of Bactrocera dorsalis (Hendel) (Diptera: Tephritidae)

Reliable methods are needed to ascertain sexual maturity of field captured tephritid fruit flies. To provide such a tool for female Oriental fruit flies, this study documented the changes in ovarian development at different age intervals (1, 3, 6, 11, 15, 18, 20, 21, 23, 26, 30, 35, 40, 45, 52, 55 and 78 day old) of Bactrocera dorsalis (Hendel). As fly ages, the differences in morphological characters of female reproductive system were assessed visually and the ovarian maturation process was broadly classified into various developmental stages namely previtellogenesis (stage 1 and 2); vitellogenesis (stage 3 and 4), appearance of mature egg (stage 5) and post-oviposition (stage 6). Based on visual assessment of ovarian characters, from the day 1-6, the flies were in previtellogenic stage; from the day 7-11, the flies were in vitellogenic stage, and from the day 12-15, the flies were in late vitellogenic stage. From the day 15 onwards matured follicles were observed on the terminal end of the fly ovary. At the day 18, presence of opaque mature terminal oocyte (matured egg) was noticed in the flies confirming sexual maturity. This classification based on visual assessment of morphological changes in the ovary would help us determine the age of field collected female B. dorsalis

RNA sequencing to characterize transcriptional changes of sexual maturation and mating in the female oriental fruit fly Bactrocera dorsalis.

BackgroundFemale reproductive potential plays a significant role in the survival and stability of species, and sexual maturation and mating processes are crucial. However, our knowledge of the reproductive genes involved in sexual maturation and mating has been largely limited to model organisms. The oriental fruit fly Bactrocera dorsalis is a highly invasive agricultural pest, known to cause major economic losses; thus, it is of great value to understand the transcriptional changes involved in sexual maturation and mating processes as well as the related genes. Here, we used a high-throughput sequencing method to identify multiple genes potentially involved in sexual maturation and mating in female B. dorsalis.ResultsWe sequenced 39,999 unique genes with an average length of 883 bp. In total, 3264 differentially expressed genes (DEGs) were detected between mature virgin and immature Bactrocera dorsalis libraries, whereas only 83 DEGs were identified between flies that had mated or were mature virgins. These DEGs were functionally annotated using the GO and KEGG pathway annotation tools. Results showed that the main GO terms associated with the DEGs from the mature virgin vs. immature groups were primarily assigned to the metabolic and developmental processes, which we focused on, whereas those from the mated vs. mature virgin group largely belonged to the response to stimulus and immune system processes. Additionally, we identified multiple DEGs during sexual maturation that are involved in reproduction, and expression pattern analysis revealed that the majority DEGs detected were highly enriched in those linked to the ovaries or fat bodies. Several mating responsive genes differentially expressed after mating were also identified, and all antimicrobial peptides detected were highly enriched in fat body and significantly up-regulated approximately 2- to 10-fold at 24 h after mating.ConclusionThis study supplied female reproductive genes involved in sexual maturation and the post-mating response in B. dorsalis, based on RNA-seq. Our data will facilitate molecular research related to reproduction and provide abundant target genes for effective control of this agricultural pest.Electronic supplementary materialThe online version of this article (doi:10.1186/s12864-016-2532-6) contains supplementary material, which is available to authorized users.

Morphological Features of the Ovaries During Oogenesis of the Oriental Fruit Fly,Bactrocera dorsalis, in Relation to the Physiological State

Determination of physiological state in insects is useful in furthering the understanding of how insect behavior changes with age. Central to this determination is the identification of characters that allow assessment of physiological age. While non-destructive measures produce the most desired outcomes, internal markers may be more diagnostic and reliable. In this study, key morphological characters during previtellogenesis through vitellogenesis and ovulation were assessed as markers to determine physiological states of the oriental fruit fly, Bactrocera dorsalis (Hendel) (Diptera: Tephritidae). Ovary length and width, ovarian index (length × width), and egg load of laboratory-reared B. dorsalis females recorded daily from eclosion up to 80 days old suggested significant differences in the ovarian index and egg load between females from each oogenesis stage. Parity status determined by the presence of follicular relics was found to provide high-accuracy classifications for B. dorsalis females. The presence of follicular relics with distinct morphological features provides a reliable identification tool to determine the physiological state of wild female oriental fruit fly. The potential applications of this technique to identify the physiological age of female fruit flies to study behavioral attributes in their natural habitat, and also the potential applications in relation to field control, are discussed.

Low Diversity Bacterial Community and the Trapping Activity of Metabolites from Cultivable Bacteria Species in the Female Reproductive System of the Oriental Fruit Fly, Bactrocera dorsalis Hendel (Diptera: Tephritidae)

Our goal was to identify the bacteria inhabiting the reproductive system of the female oriental fruit fly, Bactrocera dorsalis (Hendel), and evaluate the chemotaxis of B. dorsalis to the metabolites produced by the bacteria. Based on 16S rRNA-based polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE), 18 operational taxonomic units (OTUs) were assigned to the five bacterial classes Betaproteobacteria, Alphaproteobacteria, Gammaproteobacteria, Bacilli and Actinobacteria. Nine OTUs were assigned to Gammaproteobacteria, which was the most highly represented class. Enterobacteriaceae constituted the dominant family, and within this family, three genera and five species were identified, including Enterobacter sakazakii, Klebsiella oxytoca, Klebsiella pneumoniae, Raoultella terrigena and Enterobacter amnigenus. In this set, the first two species were the dominant components, and the latter three species were the minor ones. Finally, we found that the metabolites produced by R. terrigena, K. oxytoca and K. pneumoniae were attractive to the B. dorsalis adults, and in field studies, B. dorsalis adults were most attracted to K. oxytoca. Collectively, our results suggest that the female reproductive system plays an important role in the transfer of enterobacteria from the gut to fruit. Our data may prompt the development of a female-targeted population control strategy for this fly.

A comparative assessment of the response of three fruit fly species (Diptera: Tephritidae) to a spinosad-based bait: effect of ammonium acetate, female age, and protein hunger

Ammonia-releasing substances are known to play an important role in fruit fly (Diptera: Tephritidae) attraction to food sources, and this information has been exploited for the development of effective synthetic food-based lures and insecticidal baits. In field studies conducted in Hawaii, we examined the behavioural response of wild female oriental fruit fly (Bactrocera dorsalis (Hendel)), melon fly (B. cucurbitae (Coquillett)), and Mediterranean fruit fly (Ceratitis capitata (Wiedemann)) to spinosad-based GF-120 NF Naturalyte Fruit Fly Bait(©) formulated to contain either 0, 1 or 2% ammonium acetate. Use of visually-attractive yellow bait stations for bait application in the field allowed for proper comparisons among bait formulations. Field cage tests were also conducted to investigate, using a comparative behavioural approach, the effects of female age and protein starvation on the subsequent response of F1 generation B. cucurbitae and B. dorsalis to the same three bait formulations that were evaluated in the field. Our field results indicate a significant positive effect of the presence, regardless of amount, of AA in GF-120 for B. dorsalis and B. cucurbitae. For C. capitata, there was a significant positive linear relationship between the relative amounts of AA in bait and female response. GF-120 with no AA was significantly more attractive to female C. capitata, but not to female B. dorsalis or B. cucurbitae, than the control treatment. Our field cage results indicate that the effects of varying amounts of AA present in GF-120 can be modulated by the physiological stage of the female flies and that the response of female B. cucurbitae to GF-120 was consistently greater than that of B. dorsalis over the various ages and levels of protein starvation regimes evaluated. Results are discussed in light of their applications for effective fruit fly suppression.

Comparison of Rain-Fast Bait Stations Versus Foliar Bait Sprays for Control of Oriental Fruit Fly,Bactrocera dorsalis, in Papaya Orchards in Hawaii

Bait stations represent an environmentally friendly attract-and-kill approach to fruit fly population suppression. Recently a novel, visually attractive, rain-fast bait station was developed in Hawaii for potential use against multiple species of pestiferous fruit flies. Here, we compared the efficacy of GF-120 NF Naturalyte Fruit Fly Bait applied either as foliar sprays or onto bait stations in reducing female oriental fruit fly, Bactrocera dorsalis (Hendel) (Diptera: Tephritidae), population density and level of fruit infestation in commercial papaya orchards in Hawaii. Trapping and infestation data were used as indicators of the effectiveness of the two bait application methods. For the first 10 weeks of the study, captures of female B. dorsalis in monitoring traps were significantly greater in control plots than in plots treated with foliar sprays or bait stations. Six weeks after the first bait spray, incidence of infestation (i.e. number of fruit with one or more B. dorsalis larvae) of quarter to half-ripe papaya fruit was reduced by 71.4% and 63.1% for plots with bait stations and foliar sprays, respectively, as compared to control plots. Twelve weeks after first spray, incidence of infestation was reduced by only 54.5% and 45.4% for plots with bait stations and foliar sprays, respectively, as compared to control plots. About 42% less GF-120 was used in orchard plots with bait stations compared to those subject to foliar sprays. The impact of field sanitation on the outcome is also discussed. The results indicate that bait stations can provide a simple, efficient, and economical method of applying insecticidal baits to control fruit flies and a safer alternative to foliar sprays.

Managing Oriental Fruit Fly (Diptera: Tephritidae), With Spinosad-Based Protein Bait Sprays and Sanitation in Papaya Orchards in Hawaii

The efficacy of GF-120 NF Naturalyte Fruit Fly Bait in combination with field sanitation was assessed as a control for female oriental fruit fly, Bactrocera dorsalis (Hendel) (Diptera: Tephritidae), in papaya (Carica papaya L.) orchards in Hawaii. Three different bait spray regimes were evaluated: every row (high use of the bait), every fifth row (moderate use), and every 10th row (low use). Orchard plots in which no bait was applied served as controls. For five of the seven biweekly periods that followed the first bait spray, trapping data revealed significantly fewer female B. dorsalis captured in plots subject to high and moderate bait use than in control plots. Differences in incidence of infestation among treatments were detected only by the third (12 wk after first spray) fruit sampling with significantly fewer infested one-fourth to one-half ripe papaya fruit in plots subject to high and moderate bait use than in control plots. Parasitism rates by Fopius arisanus (Sonan) (Hymenoptera: Braconidae) were not negatively affected by bait application. Results indicate that foliar applications of GF-120 NF Naturalyte Fruit Fly Bait either to all rows (every other tree), or to every fifth row (every tree) in combination with good sanitation can effectively reduce infestation by B. dorsalis in papaya orchards in Hawaii.

Distribution and Abundance of Female Oriental Fruit Flies Near Methyl Eugenol-Baited Traps

Methyl eugenol is an extremely effective attractant for male oriental fruit flies, Bactrocera dorsalis (Hendel). Field experiments were conducted in a commercial guava orchard to determine whether the presence of methyl eugenol-baited traps affected the distribution and abundance of female oriental fruit flies near the traps. Captures of females on spheres did not increase within the vicinity of methyl eugenol-baited traps. Captures of males were significantly greater on spheres hung in trees containing methyl eugenol-baited traps than on spheres hung in other trees. An experiment was conducted to determine if methyl eugenol would influence the dispersal of unmated, sexually mature female oriental fruit flies. There were no significant differences in the numbers of marked or wild females captured on traps at different distances from the methyl eugenol lure. This study did not find any evidence that the presence of methyl eugenol-baited traps in orchards would affect female abundance in the vicinity of traps.

Responses of Female Oriental Fruit Flies (Diptera: Tephritidae) to Protein and Host Fruit Odors in Field Cage and Open Field Tests

The attraction of female oriental fruit flies, Bactrocera dorsalis (Hendel), to protein and host fruit odors was examined in field-cage and field experiments. In field-cage experiments, we examined how the physiological state of laboratory-cultured female oriental fruit flies affected their responses to protein (Nu-Lure) and fruit (orange) odors. Both mated and unmated, protein-fed females (10–12 d old) were more attracted to fruit odors than to protein odors, whereas mated, protein-deprived females (10–12 d old) and unmated, protein-fed females (2–3 d old) were equally attracted to fruit and protein odors. The combination of fruit and protein odors was less attractive to protein-fed females than fruit odors alone. Field tests were conducted to compare capture rates of wild oriental fruit flies in traps baited with commercially available protein baits, Nu-Lure, Trece A.M. Supercharger, and BioLure, and in traps baited with either fruit (orange) or Nu-Lure in a commercial guava orchard. Spheres baited with either Supercharger or BioLure captured more female oriental fruit flies than unbaited spheres when the lures were hung above spheres. Traps baited with Nu-Lure were more effective for capturing females than traps baited with orange puree in field tests.

Visual Stimuli and the Response of Female Oriental Fruit Flies (Diptera: Tephritidae) to Fruit-Mimicking Traps

Experiments were conducted to determine the response of female oriental fruit flies, Bactrocera dorsalis (Hendel), and 2 fruit fly parasitoids, Fopius arisanus (Sonan) and Diachasmimorpha longicaudata (Ashmead), to the color, shape, and size of visual sticky traps. Numbers of females captured on yellow spheres increased as sphere size increased with diameters of 5–11 cm. Preference of females for yellow spheres over green and red spheres was positively correlated with sphere size. Yellow-colored spheres and rectangular blocks of equivalent surface area were equally attractive to females; however, females were more attracted to red spheres than to red blocks of equivalent surface area. The influence of background colors on the attractiveness of spheres was investigated by comparing the response of flies to 8 color combinations of the panels and spheres of Ladd traps. Standard Ladd traps, with red spheres attached to the center of yellow panels, captured more females than any other trap tested and could be used to monitor populations of oriental fruit flies in orchards. Female oriental fruit flies may be attracted to standard Ladd traps because of the visual contrast of red spheres against a light background.

Socially facilitated egglaying behavior in Mediterranean fruit flies

We examined the behavior of individual mature female Mediterranean fruit flies (medflies), Ceratitis capitata (Wiedemann), transferred from a holding cage without fruit to a clean host kumquat fruit already occupied by another medfly female engaged in ovipositional behavior. A significantly greater proportion of transferred (=test) ovipositionally naive females initiated ovipositor boring into a fruit in the presence than in the absence of an occupying medfly. Moreover, test females commenced boring significantly sooner in the presence than in the absence of another medfly. Interestingly, similar results occurred when a test medfly was transferred to a kumquat occupied by an ovipositing female oriental fruit fly, Bactrocera dorsalis Hendel. In contrast, there was no enhancement of propensity to bore when a test medfly was transferred to a kumquat occupied by a female Biosteres arisanus (Sonan), a parasitoid attacking medfly eggs. The principal proximate stimulus giving rise to the higher tendency to oviposit of a test medfly in the presence of an occupying medfly or oriental fruit fly appeared to be wing-waving by the occupant during an encounter. We consider our findings to be good evidence of socially facilitated ovipositional behavior in ovipositionally naive medflies, and suggest that such females may benefit from acquisition of a cue demonstrating the acceptability of a host for oviposition.

Attraction of Female Oriental Fruit Fly, Bactrocera dorsalis, to Volatile Semiochemicals from Leaves and Extracts of a Nonhost Plant, Panax (Polyscias guilfoylei) in Laboratory and Olfactometer Assays

Fresh whole leaves and solvent–water leaf extracts of the hedgerow plant panax, Polyscias guilfoylei (Bull), were tested for their attractiveness to male and female Oriental fruit flies, Bactrocera dorsalis, in laboratory flight tunnel and cage olfactometer bioassays. Fresh mature whole panax leaves were found to be attractive to mated female oriental fruit flies in the flight tunnel. Response of males and virgin females was low and in most instances not significantly different from controls. Attraction of mated female flies to the layers resulting from a methylene chloride–water partition or a hexane–water partition of freshly ground leaves using small McPhail traps was greatest in the methylene chloride fraction. When methylene chloride and water layers were tested competitively in a multiple-choice rotating olfactometer, the methylene chloride fraction was more attractive. Tests involving the methylene chloride–water interface (an emulsion of the two partitioned layers) with and without a standard attractant NuLure, showed the emulsion layer to be significantly more attractive than the other fractions or NuLure. In outdoor cage olfactometer assays of methylene chloride and water fractions, activity was greatest in the methylene chloride fraction. The results suggests that volatile semiochemicals from this nonhost plant are attractive to mated female Oriental fruit flies. The results are discussed in relation to the chemical ecology of B. dorsalis and the potential use of this nonhost plant for detection and control of female Oriental fruit flies in the field.

Translocation-Based Genetic Sexing System for the Oriental Fruit Fly (Diptera: Tephritidae) Based on Pupal Color Dimorphism

The autosomal recessive white puparium (wp) mutant was used to construct the first genetic sex sorting system in the oriental fruit fly, Bactrocera dorsalis (Hendel). The translocation stocks have females with the white puparium phenotype and puparia of males are the wild-type color, brown. Viability measurements of the 49-wp translocation strain indicate that fitness relative to the wild-type and white puparium strains was not lower than expected. Hatch rate and larval viability were lower for the translocation strain, but there were no significant differences between strains for eclosion rates. This translocation-based sex sorting system is the only automatic method currently available for separation of male and female oriental fruit flies in sterile insect release programs.

Intra‐tree foraging behavior of Dacus dorsalis flies in relation to host fruit quantity, quality and type

AbstractWe observed the fruit foraging behavior of mature female oriental fruit flies, Dacus dorsalis Hendel (Diptera, Tephritidae), released individually onto potted field‐caged host trees containing fruit of different quality, quantity, or type (no fruit, 3 or 12 uninfested kumquats, 12 infested kumquats, or 3 uninfested sweet oranges). Our findings were largely consistent with foraging‐behavior theory, and with previous results for Mediterranean fruit fly, Ceratitis capitata (Wiedemann), and the apple maggot fly, Rhagoletis pomonella (Walsh): (1) flies left fruitless trees soon after release, (2) more flies visited fruit, and flies visited more fruit and spent more time on trees with increasing fruit density, and (3) Giving Up Time (time between last oviposition and leaving the tree) was significantly greater for flies visiting infested fruit than for those visiting uninfested fruit. Oriental fruit flies declined to oviposit in fruit containing conspecific larvae.

Behavioral responses of female oriental fruit flies to the odor of papayas at three ripeness stages in a laboratory flight tunnel (Diptera: Tephritidae)

Behavioral responses of adult female oriental fruit flies, Dacus dorsalisHendel, to the odor of papayas from three ripeness classes were studied using a threechoice flight tunnel bioassay. Laboratoryreared flies were allowed to respond freely to any of three papaya odors (mature green, colorbreak to one-fourth ripe, and one-half to full ripe) emanating from identical (spherical) fruit models. Five behaviors were measured in assessing the fly's relative attraction to the odors (number of landings), arrestment (total fly seconds on sphere), fly-fly interactions on the fruit model (maximum and modal fly density), and acceptance for oviposition (total eggs laid). Females showed no significant difference in total fly landings based on all age classes combined. Significant differences were noted among age classes. Females spent more total time on the sphere and showed a higher maximum density and modal fly density to ripe fruit than to green fruit odors. Ovipositional acceptance of fruit models based on the total number of eggs laid in a sphere was greater in response to the ripefruit odor than to the other two odor classes. Olfactorystimulated behavioral responses of females to the odor of ripe papayas were significantly different from the other ripeness classes for all behaviors at 8 days postemergence and then declined in 11-day-old flies. Behavioral responses were greater during the afternoon than in the morning. Observations of wild oriental fruit flies to papayas in the field indicated a preference for residing on riper fruit. The results of this study are discussed with regard to the role of olfactory inputs generated by the odor of ripening fruit on female attraction and oviposition behavior resulting in infestation of papayas by oriental fruit fly.