Fruit Volatiles Research Articles

Divergent preferences of Rhagoletis pomonella host races for olfactory and visual fruit cues

AbstractThe apple and hawthorn‐infesting host races of Rhagoletis pomonella Walsh (Diptera: Tephritidae) represent a model for incipient sympatric speciation. Recent studies have shown that apple and hawthorn flies differ in their responses to host‐fruit odor. Each host race preferentially orients to the volatile chemicals emanating from the surface of its natal fruit and is antagonized by non‐natal fruit volatiles. Fruit odor discrimination is evolutionarily important due to its contributory role in host‐specific mating, generating partial premating reproductive isolation between the races in sympatry. Visual cues are also involved in R. pomonella host searching, yet the extent to which they are used to discriminate between hosts has not been fully resolved, nor has their interaction with olfactory cues. Here, we report results from a series of two‐way choice experiments conducted in the field on resident apple and hawthorn flies at a site near Fennville, MI, USA. Four key findings emerged from the study: (1) both olfactory and (2) visual cues increased host discrimination of apple and hawthorn flies for their respective natal fruit, (3) the presence of a single appropriate volatile blend on a natal or non‐natal visual model generally increased the ability of flies to discriminate for their natal fruit, and (4) the presence of both natal and non‐natal olfactory cues on fruit models did not enhance host discrimination above levels observed for visual models alone. We discuss the implications of our results for interpreting the findings of two‐way host choice experiments and for sympatric speciation in phytophagous insects.

Olfactory Shifts Parallel Superspecialism for Toxic Fruit in Drosophila melanogaster Sibling, D. sechellia

Olfaction in the fruit fly Drosophila melanogaster is increasingly understood, from ligand-receptor-neuron combinations to their axonal projection patterns into the antennal lobe . Drosophila thus offers an excellent opportunity to study the evolutionary and ecological dynamics of olfactory systems. We compared the structure and function of the generalist D. melanogaster with that of specialist D. sechellia, which oviposits exclusively on morinda fruit . Our analyses show that whereas the fruit's headspace was dominated by acids, antennae responded most strongly to hexanoates. D. sechellia exhibited an extraordinarily strong response to methyl hexanoate (MeHex). Behaviorally, D. sechellia was much more attracted to these morinda fruit volatiles than was D. melanogaster. The high sensitivity to MeHex was paralleled by a 2.5x-3 x overrepresentation of MeHex neurons on the antenna and a concordant 2.9 x increase in volume of the corresponding glomerulus as compared to D. melanogaster. In addition, the MeHex neuron exhibited an extreme sensitivity down to femtograms of its ligand. In contrast, no peripherally mediated shift was found paralleling D. sechellia's increased attraction to acids. These findings are a demonstration of evolution acting at several levels in the olfactory circuitry in mediating a fruit fly's unique preference for fruit toxic to its sibling species .

The chemosensory basis for behavioral divergence involved in sympatric host shifts. I. Characterizing olfactory receptor neuron classes responding to key host volatiles

The recent shift of Rhagoletis pomonella from its native host hawthorn to introduced, domestic apple has been implicated as an example of sympatric speciation. Recent studies suggest that host volatile preference might play a fundamental role in host shifts and subsequent speciation in this group. Single sensillum electrophysiology was used to test a proposed hypothesis that differences in R. pomonella olfactory preference are due to changes in the number or odor specificity of olfactory receptor neurons. Individuals were analyzed from apple, hawthorn, and flowering dogwood-origin populations, as well as from the blueberry maggot, Rhagoletis mendax Curran (an outgroup). Eleven compounds were selected as biologically relevant stimuli from previous electroantennographic/behavioral studies of the three R. pomonella populations to host fruit volatiles. Cluster analysis of 99 neuron responses showed that cells from all tested populations could be grouped into the same five classes, ranging from those responding to one or two volatiles to those responding to several host volatiles. Topographical mapping also indicated that antennal neuron locations did not differ by class or fly taxa. Our results do not support the hypothesis that differences in host preference among Rhagoletis populations are a result of alterations in the number or class of receptor neurons responding to host volatiles.

The chemosensory basis for behavioral divergence involved in sympatric host shifts II: olfactory receptor neuron sensitivity and temporal firing pattern to individual key host volatiles

The Rhagoletis species complex has been a key player in the sympatric speciation debate for much of the last 50 years. Studies indicate that differences in olfactory preference for host fruit volatiles could be important in reproductively isolating flies infesting each type of fruit via premating barriers to gene flow. Single sensillum electrophysiology was used to compare the response characteristics of olfactory receptor neurons from apple, hawthorn, and flowering dogwood-origin populations of R. pomonella, as well as from the blueberry maggot, R. mendax (an outgroup). Eleven volatiles were selected as stimuli from behavioral/electroantennographic studies of the three R. pomonella host populations. Previously, we reported that differences in preference for host fruit volatile blends are not a function of alterations in the general class of receptor neurons tuned to key host volatiles. In the present study, population comparisons involving dose-response trials with the key volatiles revealed significant variability in olfactory receptor neuron sensitivity and temporal firing pattern both within and among Rhagoletis populations. It is concluded that such variability in peripheral sensitivity and temporal firing pattern could influence host preference and contribute to host fidelity and sympatric host shifts in the Rhagoletis complex.

A Novel Approach for Nontargeted Data Analysis for Metabolomics. Large-Scale Profiling of Tomato Fruit Volatiles

To take full advantage of the power of functional genomics technologies and in particular those for metabolomics, both the analytical approach and the strategy chosen for data analysis need to be as unbiased and comprehensive as possible. Existing approaches to analyze metabolomic data still do not allow a fast and unbiased comparative analysis of the metabolic composition of the hundreds of genotypes that are often the target of modern investigations. We have now developed a novel strategy to analyze such metabolomic data. This approach consists of (1) full mass spectral alignment of gas chromatography (GC)-mass spectrometry (MS) metabolic profiles using the MetAlign software package, (2) followed by multivariate comparative analysis of metabolic phenotypes at the level of individual molecular fragments, and (3) multivariate mass spectral reconstruction, a method allowing metabolite discrimination, recognition, and identification. This approach has allowed a fast and unbiased comparative multivariate analysis of the volatile metabolite composition of ripe fruits of 94 tomato (Lycopersicon esculentum Mill.) genotypes, based on intensity patterns of >20,000 individual molecular fragments throughout 198 GC-MS datasets. Variation in metabolite composition, both between- and within-fruit types, was found and the discriminative metabolites were revealed. In the entire genotype set, a total of 322 different compounds could be distinguished using multivariate mass spectral reconstruction. A hierarchical cluster analysis of these metabolites resulted in clustering of structurally related metabolites derived from the same biochemical precursors. The approach chosen will further enhance the comprehensiveness of GC-MS-based metabolomics approaches and will therefore prove a useful addition to nontargeted functional genomics research.

Captures of <I>Rhagoletis mendax</I> and <I>R. cingulata</I> (Diptera: Tephritidae) on Sticky Traps Are Influenced by Adjacent Host Fruit and Fruit Juice Concentrates

Field trapping studies were conducted to determine whether feral blueberry maggot flies, Rhagoletis mendax Curran, and Eastern cherry fruit flies, R. cingulata (Loew), respond to natal host-fruit volatiles. Subsequent experiments were conducted to evaluate the potential of using simple and inexpensive fruit juice concentrate lures to monitor these key pests of blueberries and cherries, respectively. The presence of ripe blueberries and ripe tart cherries in enclosures that permitted escape of fruit volatiles significantly increased captures of R. mendax and R. cingulata, respectively, on adjacent sticky traps compared with traps without adjacent fruit. R. mendax were not affected by addition of blueberry concentrate to Pherocon AM traps with or without ammonium acetate. Pherocon AM boards prebaited with ammonium acetate directly incorporated into the sticky Tangle-Foot coating were equally effective as unbaited Pherocon AM boards deployed with separate ammonium acetate dispensers for monitoring R. mendax. A cherry juice concentrate increased captures of R. cingulata on unbaited Pherocon AM but not Rebell traps. In addition, combining cherry juice concentrate and ammonium acetate on Pherocon AM traps increased captures of R. cingulata compared with captures on traps with either stimulus alone. Adding ammonium acetate lures to Rebell traps more than doubled captures of R. cingulata over that on unbaited Rebell traps. Our results show that feral R. mendax and R. cingulata flies are attracted to the volatiles emitted from their host fruit and that this may be exploited to improve monitoring of these important fruit pests.

Captures ofRhagoletis mendaxandR. cingulata(Diptera: Tephritidae) on Sticky Traps Are Influenced by Adjacent Host Fruit and Fruit Juice Concentrates

Field trapping studies were conducted to determine whether feral blueberry maggot flies, Rhagoletis mendax Curran, and Eastern cherry fruit flies, R. cingulata (Loew), respond to natal host-fruit volatiles. Subsequent experiments were conducted to evaluate the potential of using simple and inexpensive fruit juice concentrate lures to monitor these key pests of blueberries and cherries, respectively. The presence of ripe blueberries and ripe tart cherries in enclosures that permitted escape of fruit volatiles significantly increased captures of R. mendax and R. cingulata, respectively, on adjacent sticky traps compared with traps without adjacent fruit. R. mendax were not affected by addition of blueberry concentrate to Pherocon AM traps with or without ammonium acetate. Pherocon AM boards prebaited with ammonium acetate directly incorporated into the sticky Tangle-Foot coating were equally effective as unbaited Pherocon AM boards deployed with separate ammonium acetate dispensers for monitoring R. mendax. A cherry juice concentrate increased captures of R. cingulata on unbaited Pherocon AM but not Rebell traps. In addition, combining cherry juice concentrate and ammonium acetate on Pherocon AM traps increased captures of R. cingulata compared with captures on traps with either stimulus alone. Adding ammonium acetate lures to Rebell traps more than doubled captures of R. cingulata over that on unbaited Rebell traps. Our results show that feral R. mendax and R. cingulata flies are attracted to the volatiles emitted from their host fruit and that this may be exploited to improve monitoring of these important fruit pests.

Volatile compounds from pitanga fruit ( Eugenia uniflora L.)

Extracts from pitanga leaves are considered to be effective against many diseases, and are therefore used in popular Brazilian medicines. In this study, the volatile constituents of pitanga fruits ( Eugenia uniflora L.) were trapped on to Porapak-Q and eluted with ethyl acetate, and the chemical composition of the extract was analyzed by gas chromatography and gas chromatography/mass spectrometry. Fifty-four compounds were detected, and twenty-nine of those were identified by close matches with standard MS spectra. Monoterpenes (75.3% in mass) were found to comprise the largest class of the pitanga fruit volatiles, including trans-β-ocimene (36.2%), cis-ocimene (13.4%), the isomeric β-ocimene (15.4%) and β-pinene (10.3%). Several known therapeutic constituents of pitanga leaf extract, such as selina-1,3,7(11)-trien-8-one (the major constituent) were also found to be present in the fruit volatile extract, suggesting that the fruit may display therapeutic properties similar to those of the leaf extract.

Role of Ethylene in the Biosynthetic Pathways of Aroma Volatiles in Ripening Fruit

During the past decade, fruit aroma biosynthetic pathways were established in some climacteric fruits, such as tomato, apple, and melon. Inhibition of ethylene biosynthesis or its action in these fruits can reduce the production of fruit volatiles. Furthermore, ethylene partially regulates expression of a few important enzyme genes in fruit volatile biosynthetic pathways. The aim of this review is to bring together recent advances for understanding the regulatory role of ethylene in the biosynthesis of aroma volatiles in some fruits.

Single experience learning of host fruit selection by lepidopteran larvae

Neonate larvae of a lepidopteran, the codling moth ( Cydia pomonella L.) search for their host fruit after hatch. The process of host searching is known to be activated by kairomones contained in host fruit volatiles, but the mechanism of actual selection and infestation of the fruit is unclear. Here we show that lepidopteran neonates can utilize single experience learning in selection and infestation of host apple. We found that the process of host fruit selection may be modified by single experience learning, namely preference induction or averse conditioning. Both types of learning were acquired within 3 h of training. Experience was retained for over 3 days in the case of averse conditioning. Preference induction, a form of learning specific to insects, is expected to produce rigid host preference lasting for days if not weeks, but in codling moth neonates this type of memory was retained only for 3 h. We speculate that conjunction of preference induction with short retention time and averse conditioning with long retention time provide an optimal adaptive strategy of host fruit selection for codling moth neonates.

Interactive Responses of Gala Apple Fruit Volatile Production to Controlled Atmosphere Storage and Chemical Inhibition of Ethylene Action

Gala apples exposed to the ethylene action inhibitor 1-methylcyclopropene (1-MCP) for 12 h at 20 degrees C were stored at 1 degrees C in air or a controlled atmosphere (CA) maintained at 1 kPa O2 and 2 kPa CO2. Volatile compounds were measured after 4, 12, 20, and 28 weeks plus 1 or 7 days at 20 degrees C. Treatment with 1-MCP and then storage in air or CA or storage in CA without 1-MCP treatment reduced volatile production as compared to apples not treated with 1-MCP stored in air. The reduced production of esters, alcohols, aldehydes, acetic acid, and 1-methoxy-4-(2-propenyl)benzene was observed. Ester production by fruit stored in CA decreased throughout the storage period regardless of previous 1-MCP treatment. The production of esters, alcohols, aldehydes, acetic acid, and 1-methoxy-4-(2-propenyl)benzene by 1-MCP-treated fruit stored in air plus 7 days at 20 degrees C increased after 20 or 28 weeks of storage. Continuous exposure to 417 micromol m(-3) ethylene for 7 days at 20 degrees C after 12 or 28 weeks of storage stimulated production of many volatile compounds, primarily esters and alcohols, by fruit stored in CA or 1-MCP-treated apples stored in air. However, exposure to ethylene had no effect on the production of aldehydes or acetic acid.

Specificity of Codling Moth (Lepidoptera: Tortricidae) for the Host Plant Kairomone, Ethyl (2E,4Z)-2,4-Decadienoate: Field Bioassays with Pome Fruit Volatiles, Analogue, and Isomeric Compounds

Codling moth, Cydia pomonella (L.), is a severe pest of apples, pears, and walnuts worldwide, and new approaches for precise monitoring and management would be beneficial. Ninety-two pome fruit volatiles were formulated in 23 distinct blends, of which a single 4-component blend of 10-carbon esters showed the only significant attraction of moths in field bioassays conducted in both walnut and apple orchards. A single constituent of this blend, ethyl (2E,4Z)-2,4-decadienoate--the "pear ester", was the major contributing attractant. The pear ester attracted both male and female moths in combined numbers that were comparable to the attractiveness of conspecific sex pheromone. Structure-activity tests were conducted in a series of orchard trials to determine the specificity of attraction of codling moths to the pear ester kairomone. No analogue 10-carbon alcohols, aldehydes, acetates, or other esters elicited significant moth capture responses. Tests with various analogue esters with alcohol chain length moiety substitutions of the (2E,4Z)-2,4-decadienoic acid elicited differential capture responses, with the ethyl exceeding the propyl, methyl, butyl, and hexyl analogues. The (E,Z) geometric isomers of this series of (2E,4Z)-2,4-decadienoic acid esters far exceeded the attractiveness of the (E,E) isomers. The pear ester is a potent attractant of both males and females, and codling moths are highly discriminating and specific in their structure-activity-based attraction to this pear-derived kairomone. These specificity attributes should allow this host plant kairomone to contribute to new abilities for female monitoring and the potential of development of novel and highly selective control practices that should decrease the current dependence on the use of broad-spectrum insecticides.

Parasitoid exploitation of the seasonal variation in host plant volatile emission for herbivore location

AbstractVolatile compounds from the apple, Malus domestica Borkh. (Rosaceae), change considerably as the season progresses, and this is successfully exploited by the female codling moth Cydia pomonella L. (Lepidoptera, Tortricidae), as it searches for oviposition sites. In this study, we investigated the effect of seasonal emissions of apple fruit volatiles on the host location behaviour of a parasitoid of the codling moth larvae, Hyssopus pallidus (Askew) (Hymenoptera: Eulophidae). In dual choice olfactory bioassays, the behaviour of the parasitoid in response to apple cues was observed over the complete 2003 growing season. Our results show that codling moth infested apples evoked a strong response from the parasitoid at the beginning of the season, until July. Then, attraction dropped drastically, increasing again at the beginning of August. At the end of the growing season, just prior to harvest, infested apples hardly evoked any behavioural response. Interestingly enough, mid‐season emissions of healthy apples were per se attractive to the parasitoid, and even preferred over volatiles from infested apples. Simultaneous volatile collections from healthy apples on twigs in the field were analysed throughout the season, showing that the overall quantity of headspace volatiles peaks at the beginning of June and mid‐August. The seasonal volatile emission is correlated with the behaviour of the parasitoid during the fruit ripening stage. The results are discussed in relation to the use of H. pallidus as a potential biocontrol agent, in order to enhance current integrated pest management (IPM) programs.

Carbon dioxide diminishes cold tolerance of third instar larvae of Ceratitis capitata Wiedemann (Diptera: Tephritidae) in ‘Fortune’ mandarins: implications for citrus quarantine treatments

The use of a carbon dioxide treatment as a complement to the standard cold disinfestation quarantine treatment against Ceratitis capitata in ‘Fortune’ mandarin fruit was investigated. A 95% carbon dioxide atmosphere at 20 °C for 20 h before the standard cold quarantine resulted in increased levels of fruit volatiles (ethanol and acetaldehyde). However, this did not produce any detrimental effects on either fruit external appearance (color and peel texture) or the organoleptic characteristics of the fruit. The high carbon dioxide treatment reduced lethal times for C. capitata by 2.7085 (relative potency at probit 9). This treatment could be easily applied to current disinfestation facilities that are used for preparing and shipping citrus to countries where quarantine regulations are enforced. Its application would not add excessive costs, but would enormously increase the reliability of standardized protocols for export of mandarins.

Variation in Volatiles from Fruits of Mango and Marula Attractive to the Mango Fruit Fly, <i>Ceratitis cosyra</i> (Walker)

Wild mango fruit fly Ceratitis cosyra , was attracted to and oviposited preferentially on immature and mature green than ripe yellow mango fruits in the field. Volatile compounds from fruits of mango and marula, at different ripeness stages, were trapped on octadecyl reversed-phase silica. The volatile compounds were identified using gas chromatography, gas chromatography-mass spectrometry and by chromatographic comparisons with authentic samples. Immature and mature green mango fruits on trees emitted similar compounds, comprising of monoterpenoids and sesquiterpenoids. A detached mature green mango fruit emitted a few esters in addition to monoterpenes and sesquiterpenes. The ripe yellow mango fruit emitted large quantities of esters and smaller proportions of terpenoids. Several esters, similar to ripe yellow mangoes, were identified in volatiles of ripe yellow marula fruits. A total of 17 terpenoids and 19 esters were identified. Some of the identified compounds in green mangoes, particularly the terpenoids, constitute candidate kairomones for C. cosyra . Key Words: Ceratitis cosyra , mango, marula, fruits, volatiles, kairomones, oviposition. East & Central African Journal of Pharmaceutical Sciences Vol.6(1) 2003:3-8

Identification of Potent Odorants in Different Cultivars of Snake Fruit [Salacca zalacca (Gaert.) Voss] Using Gas Chromatography−Olfactometry

Three cultivars of snake fruits, Pondoh Hitam, Pondoh Super, and Gading, were freshly extracted using liquid-liquid extraction. The aroma compounds of the three samples were analyzed by GC-MS and GC-olfactometry using the nasal impact frequency (NIF) method. A total of 24 odor-active compounds were associated with the aroma of snake fruit. Methyl 3-methylpentanoate was regarded as the character impact odorant of typical snake fruit aroma. 2-Methylbutanoic acid, 3-methylpentanoic acid, and an unknown odorant with very high intensity were found to be responsible for the snake fruit's sweaty odor. Other odorants including methyl 3-methyl-2-butenoate (overripe fruity, ethereal), methyl 3-methyl-2-pentenoate (ethereal, strong green, woody), and 2,5-dimethyl-4-hydroxy-3[2]-furanone (caramel, sweet, cotton candy-like) contribute to the overall aroma of snake fruit. Methyl dihydrojasmonate and isoeugenol, which also have odor impact, were identified for the first time as snake fruit volatiles. The main differences between the aroma of Pondoh and Gading cultivars could be attributed to the olfactory attributes (metallic, chemical, rubbery, strong green, and woody), which were perceived by most of the panelists in the Pondoh samples but were not detected in the Gading samples. This work is a prerequisite for effective selection of salak genotypes with optimal aroma profiles for high consumer acceptance.

Antagonist effects of non‐host fruit volatiles on discrimination of host fruit by Rhagoletis flies infesting apple (Malus pumila), hawthorn (Crataegus spp.), and flowering dogwood (Cornus florida)

AbstractIn previous flight‐tunnel tests Rhagoletis pomonella (Walsh) (Diptera: Tephritidae) flies originating from domestic apple (Malus pumila), hawthorn (Crataegus spp.), and flowering dogwood (Cornus florida), displayed greater numbers of upwind flights to blends of volatiles identified from their natal fruit compared to non‐natal fruit. Here, we show that when certain non‐host volatiles were added to the host blend, significantly fewer apple, hawthorn, and dogwood flies exhibited sustained upwind flight to the source. Specifically, the upwind flight of apple flies to the apple blend was significantly antagonized by the addition of the hawthorn or dogwood blends, the addition of 3‐methylbutan‐1‐ol alone (a key volatile for hawthorn and dogwood flies), or the combination of 3‐methylbutan‐1‐ol and another key dogwood volatile, 1‐octen‐3‐ol. Similarly, the upwind flight of dogwood and hawthorn flies to their respective natal blends was antagonized by the addition of the apple blend or the key apple volatile butyl hexanoate. Experiments were also conducted to determine whether non‐natal fruit volatiles could disrupt the close‐range flight response of flies to the visual stimulus of fruit alone, represented by an odorless red sphere. Tests with apple‐origin flies showed that when the hawthorn blend, the dogwood blend, or the key antagonist volatiles from each (3‐methylbutan‐1‐ol and 1‐octen‐3‐ol) were added to a red sphere fruit mimic, significantly lower proportions of flies were captured, compared with captures when no odor was present. Our results support the hypothesis that agonist and antagonist properties of fruit volatiles can play an important role in host recognition/discrimination by Rhagoletis flies.

Postzygotic isolating factor in sympatric speciation in Rhagoletis flies: reduced response of hybrids to parental host-fruit odors.

Rhagoletis pomonella is a model for sympatric speciation (divergence without geographic isolation) by means of host-plant shifts. Many Rhagoletis species are known to use fruit odor as a key olfactory cue to distinguish among their respective host plants. Because Rhagoletis rendezvous on or near the unabscised fruit of their hosts to mate, behavioral preferences for fruit odor translate directly into premating reproductive isolation among flies. Here, we report that reciprocal F(1) hybrids between the apple and hawthorn host races of R. pomonella, as well as between the host races and an undescribed sibling species infesting Cornus florida (flowering dogwood) do not respond to host fruit volatiles in wind-tunnel assays at doses that elicit maximal directed flight in parental flies. The reduced ability of hybrids to orient to fruit volatiles could result from a conflict between neural pathways for preference and avoidance behaviors, and it suggests that hybrids might suffer a fitness disadvantage for finding fruit in nature. Therefore, host-specific mating may play a dual role as an important postzygotic as well as a premating reproductive barrier to isolate sympatric Rhagoletis flies.

Impact of 1-Methycyclopropene and Controlled Atmosphere Storage on Volatile Production in `Gala' Apples

`Gala' apples (Malus × domestica Borkh) were harvested at optimum maturity for long-term storage, precooled overnight at 0 °C, treated with 1 μL·L-1; 1-methylcyclopropene (1-MCP) for 24 hours at 0 °C, and then placed in controlled atmosphere (CA) to determine the storage regime that would have the least negative impact on post-storage aroma volatile production. Fruit were stored at 0° and 2.5° C in ultra low oxygen (0.6% O2 -0.6% CO2; ULOCA), low oxygen (1.2% O2 -1.2% CO2; LOCA) and standard (2.5% O2 -2.5% CO2; SCA) CA for 120 and 240 days, and in ambient air for 60, 90, 120 and 150 days. Post-storage fruit volatiles were quantified by headspace analysis using a solid-phase micro-extraction (SPME) probe and FID-GC, and key volatiles were identified by GC-MS. Fruit volatile production was greatest at harvest, and decreased thereafter for fruit held in air and CA for up to 150 or 240 days, respectively. 1-MCP treatment resulted in reduced rates of respiration, ethylene and volatile production, regardless of storage regime, and resulted in a reduced production rate of all the major volatile compounds, including esters, alcohols, acids, aldehydes and ketones. Post-storage volatile production was the least in fruits removed from 0 °C in ULO, followed by LO, SCA, and then air. 1-MCP treatment inhibited post-storage volatile production in CA- and air-stored fruit by as much as 95 percent. However, recovery of aroma was delayed significantly in fruit which had been held at 0 °C vs. 2.5 ° C, suggesting aroma volatile synthesis in `Gala' is chilling sensitive.

Parasitism behavior of three species of Eucoilinae (Hymenoptera: Cynipoidea: Figitidae) fruit fly parasitoids (Diptera) in Brazil

Eucoilinae are larval endoparasitoids of cyclorrhaphous dipterous. Several species have been associated with frugivorous larvae (Tephritidae, Lonchaeidae and Drosophilidae). Some species of these dipterous cause serious damage to fruit crops. In order to minimize their damage, Integrated Pest Management (IPM) using biological control with hymenopteran parasitoids has been used. Studies on parasitism behavior can maximize the use of parasitoids in biological control programs. Thus, this paper had as objectives (1) to study the olfactory response of Aganaspis pelleranoi (Brethes) and Dicerataspis grenadensis Ashmead to the volatile emitted by guava infested with fruit fly larvae and (2) to verify the behavioral sequence of location and evaluation of hosts by A. pelleranoi, D. grenadensis and Odontosema albinerve Kieffer in laboratory and in field conditions. Experiments in a four-armed airflow olfactometer showed that A. pelleranoi and D. grenadensis were more attracted to volatiles of fruits infested with frugivorous larvae. The behavioral sequence of Eucoilinae, in ripe guava pulp infested by frugivorous larvae, showed that A. pelleranoi and O. albinerve located the host larvae by vibrotaxis and D. grenadensis found the host larvae with the ovipositor. These results established that D. grenadensis showed specificity to larvae of the family Drosophilidae in rotting guava.