Flight Tunnel Bioassays Research Articles

Female-Produced Sex Pheromone of Tetrastichus planipennisi, a Parasitoid Introduced for Biological Control of the Invasive Emerald Ash Borer, Agrilus planipennis.

The Asian eulophid wasp Tetrastichus planipennisi is being released in North America as a biocontrol agent for the emerald ash borer (Agrilus planipennis), a very destructive invasive buprestid beetle that is devastating ash trees (Fraxinus spp.). We identified, synthesized, and tested a female-produced sex pheromone for the wasp. The key component eliciting behavioral responses from male wasps in flight tunnel bioassays was identified as (6S,10S)-(2E,4E,8E)-4,6,8,10-tetramethyltrideca-2,4,8-triene. Female specificity was demonstrated by gas chromatographic (GC) comparison of male and female volatile emissions and whole body extracts. The identification was aided by coupled gas chromatography/mass spectrometry analysis, microchemical reactions, NMR, GC analyses with a chiral stationary phase column, and matching GC retention times and mass spectra with those of synthetic standards. The tetramethyl-triene hydrocarbon was synthesized as a mixture of two enantiomeric pairs of diastereomers, and as the pure insect-produced stereoisomer. In flight-tunnel bioassays, males responded to both the natural pheromone and the chiral synthetic material by upwind flight and landing on the source. In contrast, the mixture of four stereoisomers was not attractive, indicating that one or more of the "unnatural" stereoisomers antagonized attraction. Field trials, using yellow pan traps baited with natural pheromone, captured significantly more male wasps than control traps over a four week trial. The identified pheromone could increase the efficiency and specificity of the current detection methods for Tetrastichus planipennisi and aid in the determination of parasitoid establishment at release sites.

Pollinator specialization in the enigmatic Rafflesia cantleyi: A true carrion flower with species-specific and sex-biased blow fly pollinators

The plants of the enigmatic genus Rafflesia are well known for their gigantic flowers and their floral features such as pungent floral scent and vivid dark color, which mimics the food/brood sites of carrion. However, information on the pollination biology of this plant group remains limited and mostly anecdotal. In the present paper, we studied the floral volatiles of R. cantleyi Solms-Laubach and their role in pollinator attraction. To achieve these aims, the floral scent was collected in situ in the field using a dynamic headspace method followed by chemical analysis via GC-MS. The olfactory preferences of pollinators to the identified chemical compounds, were tested singly and in blends, in flight tunnel bioassays and compared with responses to headspace floral extracts. In addition, flower-visiting calliphorid flies and the local carrion fly community were sampled and identified. Five species of calliphorid flies (subfamilies of Chrysomyinae and Calliphorinae), all females, were found on the flowers, whereas nine species were found in the traps that were baited with tainted meat in the surrounding habitat. However, only flower visitors of one blow fly species, Chrysomya chani Kurahashi, were observed to carry R. cantleyi pollen after visiting male flowers. The floral volatiles emitted by male flowers in full bloom were dominated by two sulphur-containing compounds, dimethyl disulfide (DMDS) and dimethyl trisulfide (DMTS). These were accompanied by other minor compounds such as benzenoids (4), monoterpenoids (4), trace amounts of aliphatic compounds (1), and sesquiterpenes (1). In flight-tunnel bioassays, a female-specific positive response of C. chani flies to individual DMDS, DMTS, and a blend of DMDS and DMTS was evident. Our findings suggest that R. cantleyi biochemically mimics carrion and that relative ratio of oligosulfides in the floral scent play a key role in sex-biased pollinator specialization, attracting only female C. chani carrion flies to the flowers.

Electroantennogram response and attraction of Anastrepha suspensa to volatiles of various sugar sources and aged sugar solutions

AbstractWith the aim of finding new, sugar‐based volatile attractants for economically important tephritid fruit fly species, we used electroantennography (EAG) to quantitate olfactory responses of female Caribbean fruit fly, Anastrepha suspensa (Loew) (Diptera: Tephritidae), to volatiles of six sugar sources (refined white and brown cane sugar, coconut sugar, date sugar, date jaggery, and cane panela). Laboratory‐strain and wild flies, both sexually immature and mature, were tested for EAG responses to the volatiles of dry crystallized sugar sources and 10% (wt/vol) aqueous solutions that had aged in the laboratory for 0–7 days. In general, wild flies exhibited higher EAG responses than laboratory flies, and immature females responded more strongly than mature females. With the exception of date jaggery and cane panela, volatiles of dry sugar sources and 0‐ and 1‐day‐old solutions elicited lower EAG responses than any of the aged solutions. Most solution volatiles elicited the strongest EAG response after 2 days of aging. Of the treatments evaluated, volatiles of the 5‐day‐old date jaggery solution elicited the highest‐amplitude EAG responses (39%) in A. suspensa females. On the basis of the latter, we tested the attraction response of mature and immature females to date‐jaggery solutions aged over 2 and 4 days in two‐choice flight tunnel bioassays. With both mature and immature females, the 2‐day‐old solution was more attractive than the 4‐day‐old jaggery solution, but significantly more mature females (70% of captures) were attracted to 2‐day‐old jaggery solution. We discuss our results with respect to the improvement of fruit fly lures and attractants by incorporating elements from aged date‐jaggery sugar.

Development of a new attract‐and‐kill technology for Oriental fruit moth control using insecticide‐impregnated fabric

AbstractThe potential of a novel attract‐and‐kill pouch for pest control was assessed in a series of behavioral studies examining its effect on male Oriental fruit moth (OFM), Grapholita molesta (Busck) (Lepidoptera: Tortricidae). In contrast to traditional attract‐and‐kill technologies that combine insecticides and pheromones in a paste or gel, the prototype device consisted of a fabric pouch that was impregnated with deltamethrin and baited with a separate sex pheromone lure placed inside the pouch. This new approach not only provided a large insecticide‐treated surface for males to interact with but also prevented males from directly contacting the attractant, so as to minimize the risk of moths overloading their sensory system with sex pheromones. In a forced‐contact bioassay, increasing dosages of deltamethrin in the fabric from 0.02 to 0.6 mg cm−2 increased mortality or knockdown rate of OFM 2, 4, and 24 h after 5 s exposure. Likewise, duration of exposure to a deltamethrin‐treated pouch significantly affected the knockdown rate of OFM. All of the exposed moths were knocked down after 60 s exposure. In a flight tunnel bioassay, OFM males exhibited similar behaviors when offered either a control or deltamethrin‐treated pouch, indicating no repellency of the toxicant. Among the moths that contacted treated pockets, 98% was either knocked down or dead 1 h after exposure. Attract‐and‐kill pouches aged in the field for nearly a year resulted in a similar rate of knockdown of OFM compared to fresh pouches. Surprisingly, addition of a UV blocker, 2,4‐dihydroxybenzophenone, did not influence efficacy of deltamethrin in aged pouches. This simple, highly selective, and long‐lasting attract‐and‐kill device may provide an alternative control for OFM.

Male-Produced Pheromone of Spathius agrili, A Parasitoid Introduced For The Biological Control Of The Invasive Emerald Ash Borer, Agrilus planipennis

The braconid wasp, Spathius agrili, has been released in the U.S. as a biocontrol agent for the invasive emerald ash borer (Coleoptera: Buprestidae: Agrilus planipennis), a destructive pest of ash trees (Fraxinus spp.). We identified and synthesized seven male-specific volatile compounds. Three of these, dodecanal, (4R,11E)-tetradecen-4-olide, and (Z)-10-heptadecen-2-one, were the key behaviorally active components in flight tunnel bioassays. Male specificity was demonstrated by gas chromatographic comparison of male and female volatile emissions and whole body extracts. Identifications were aided by coupled gas chromatographic-mass spectrometric (GC-MS) analysis, microchemical reactions, NMR, chiral GC analysis, and GC and MS comparison with authentic standards. Both the racemic and chiral forms of the γ-lactone, as well as both E- and Z-isomers were synthesized. Flight tunnel behavioral tests showed positive male and female S. agrili responses to both natural pheromone and synthetic blends, with upwind flight and landing on the source. Large field-cage tests, using yellow sticky traps baited with pheromone, captured approximately 50% of the released male and female wasps in 24-h periods. The use of pheromone-baited traps in the field could simplify the current detection method for determining parasitoid establishment (i.e., laboriously felling and peeling ash trees for recovery of S. agrili from infested EAB larvae).

Identification of Host Fruit Volatiles from Three Mayhaw Species (Crataegus Series Aestivales) Attractive to Mayhaw-Origin Rhagoletis pomonella Flies in the Southern United States

The apple maggot fly, Rhagoletis pomonella, infests several hawthorn species in the southern USA. Here, we tested the hypothesis that these populations could serve as reservoirs for fruit odor discrimination behaviors facilitating sympatric host race formation and speciation, specifically the recent shift from downy hawthorn (Crataegus mollis) to domestic apple (Malus domestica) in the northern USA. Coupled gas chromatography and electroantennographic detection (GC-EAD), gas chromatography with mass spectrometry (GC-MS), and flight tunnel bioassays were used to identify the behaviorally active natal fruit volatile blends for three of the five major southern hawthorns: C. opaca (western mayhaw), C. aestivalis (eastern mayhaw), and C. rufula (a possible hybrid between C. opaca and C. aestivalis). A 6-component blend was developed for C. opaca (3-methylbutan-1-ol [44%], pentyl acetate [6%], butyl butanoate [6%], propyl hexanoate [6%], butyl hexanoate [26%], and hexyl butanoate [12%]); an 8-component blend for C. aestivalis (3-methylbutan-1-ol [2%], butyl acetate [47%], pentyl acetate [2%], butyl butanoate [12%], propyl hexanoate [1%], butyl hexanoate [25%], hexyl butanoate [9%], and pentyl hexanoate [2%]); and a 9-component blend for C. rufula (3-methylbutan-1-ol [1%], butyl acetate [57%], 3-methylbutyl acetate [3%], butyl butanoate [5%], propyl hexanoate [1%], hexyl propionate [1%], butyl hexanoate [23%], hexyl butanoate [6%], and pentyl hexanoate [3%]). Crataegus aestivalis and C. opaca-origin flies showed significantly higher levels of upwind directed flight to their natal blend in flight tunnel assays compared to the non-natal blend and previously developed apple, northern downy hawthorn, and flowering dogwood blends. Eastern and western mayhaw flies also were tested to the C. rufula blend, with eastern flies displaying higher levels of upwind flight compared with the western flies, likely due to the presence of butyl acetate in the C. aestivalis and C. rufula blends, an agonist compound for eastern mayhaw-origin flies, but a behavioral antagonist for western flies. The results discount the possibility that the apple fly was "pre-assembled" and originated via a recent introduction of southern mayhaw flies predisposed to accepting apple. Instead, the findings are consistent with the possibility of southern mayhaw-infesting fly host races. However, mayhaw fruits do emit several volatiles found in apple. It is, therefore, possible that the ability of the fly to evolve a preference for apple volatiles, although not the entire blend, stemmed, in part, from standing variation related to the presence of these compounds in southern mayhaw fruit.

Identification of Fruit Volatiles from Green Hawthorn (Crataegus Viridis) and Blueberry Hawthorn (Crataegus Brachyacantha) Host Plants Attractive to Different Phenotypes of Rhagoletis Pomonella Flies in the Southern United States

The apple maggot fly, Rhagoletis pomonella, infests several hawthorn species in the southern USA. In a companion paper, we showed that R. pomonella flies infesting two different mayhaw species (Crataegus opaca and C. aestivalis) can discriminate between volatile blends developed for each host fruit, and that these blends are different from previously constructed blends for northern fly populations that infest domestic apple (Malus domestica), downy hawthorn (Crataegus mollis), and flowering dogwood (Cornus florida). Here, we show by using coupled gas chromatography and electroantennographic detection (GC-EAD), gas chromatography with mass spectrometry (GC-MS), and flight tunnel bioassays, that two additional southern hawthorn fly populations infesting C. viridis (green hawthorn) and C. brachyacantha (blueberry hawthorn) also can discriminate between volatile blends for each host fruit type. A 9-component blend was developed for C. viridis (3-methylbutan-1-ol [5%], butyl butanoate [19.5%], propyl hexanoate [1.5%], butyl hexanoate [24%], hexyl butanoate [24%], pentyl hexanoate [2.5%], 1-octen-3-ol [0.5%], pentyl butanoate [2.5%], and (3E)-4,8-dimethyl-1,3,7-nonatriene (DMNT) [20.5%]) and an 8-component blend for C. brachyacantha (3-methylbutan-1-ol [0.6%], butyl acetate [50%], pentyl acetate [3.5%], butyl butanoate [9%], butyl hexanoate [16.8%], hexyl butanoate [16.8%], 1-octen-3-ol [0.3%], and pentyl butanoate [3%]). Crataegus viridis and C. brachyacantha-origin flies showed significantly higher levels of upwind oriented flight to their natal blend in flight tunnel assays compared to the alternate, non-natal blend and previously developed northern host plant blends. The presence of DMNT in C. viridis and butyl acetate in C. brachyacantha appeared to be largely responsible for driving the differential response. This sharp behavioral distinction underscores the diversity of odor response phenotypes in the southern USA, points to possible host race formation in these populations, and despite the presence of several apple volatiles in both blends, argues against a functional apple race existing on southern host plants prior to the introduction of apple to North America.

Electroantennogram and Behavioral Responses ofAnastrepha suspensa(Diptera: Tephritidae) to Putrescine and Ammonium Bicarbonate Lures

At present, the most effective synthetic lures for pest Anastrepha fruit flies are multicomponent blends that include ammonia and the diamine synergist putrescine (1,4-diaminobutane). Both chemicals generally have been regarded as protein cues that result in female-biased attraction. Using electroantennography (EAG) and flight tunnel bioassays, this study evaluated response of the Caribbean fruit fly, Anastrepha suspensa (Loew) to vapors released from commercial lure formulations of ammonium bicarbonate and putrescine. Over a range of doses tested, EAG response to ammonium bicarbonate was equivalent for both sexes, but female response was significantly greater than male response to putrescine and to a 1:1 mixture of ammonium bicarbonate and putrescine. Amplitude of EAG response to the mixture was approximately equal to the summation of responses to the individual substrates. Using a fixed dose of substrate, EAG measurements from females 1-14 d old indicated that antennal sensitivity to both lures varied according to physiological state of the fly. Peak response to ammonium bicarbonate was recorded from immature females, peak response to putrescine from sexually mature females. In bioassays, more females were captured with ammonium bicarbonate plus putrescine than with ammonium bicarbonate alone. This difference was not observed in males, resulting in a higher female to male ratio in captures with ammonium bicarbonate plus putreseine (3:1) versus ammonium bicarbonate alone (1:1). Results suggest that separate olfactory receptors are involved in detection of the two semiochemicals, and that the putrescine component is primarily responsible for the female-biased attraction.

Nitrogen and water affect direct and indirect plant systemic induced defense in cotton

Plants have direct and indirect constitutively produced and inducible defenses against herbivores and pathogens, which can substantially aid in their ability to defend themselves. However, very little is known about the influence of agronomic factors on such defenses. Here, we tested the effects of nitrogen levels and water availability on the ability of cotton plants to deter feeding by Spodoptera exigua through induction of anti-feedants, and to attract Microplitis croceipes through systemic induction of volatile emission. Cotton plants were grown with various nitrogen levels and were either exposed to water stress or normal water before being exposed to S. exigua for 48 h for induction of defenses. Dual choices of various nitrogen and water treatments were provided to M. croceipes in flight tunnel bioassays. Dual choices of leaf tissue from the various nitrogen and water treatments were provided to S. exigua larvae. Both water stress and nitrogen levels under and over the recommended levels increased leaf tissue consumption and decreased attraction of M. croceipes to the plants. Analyses of induced volatiles released from herbivore damaged plants indicate that their concentrations differ among the nitrogen levels tested with plants receiving no nitrogen or twice the recommended dose having amounts much lower than plants receiving the recommended dose. Because both direct and indirect plant defense mechanisms are negatively affected by improper nitrogen and insufficient water, we argue that these factors should be considered for a better natural control of pests in cotton and most probably in other crops.

Electrophysiological and Behavioral Responses to Chocolate Volatiles in Both Sexes of the Pyralid Moths Ephestia cautella and Plodia interpunctella

Volatiles from chocolate mediate upwind flight behavior in Ephestia cautella and Plodia interpunctella. We used gas chromatography with electroantennographic detection and found 12 active compounds derived from three different chocolate types, i.e., plain, nut-containing, and rum-flavored. Eight of the compounds were identified with mass spectrometry, and the activity of three compounds, ethyl vanillin, nonanal, and phenylacetaldehyde (PAA), was subsequently confirmed in both electrophysiological and behavioral assays. In the electroantennogram experiment, PAA and nonanal were consistently eliciting responses in both species and sexes. Ethyl vanillin was active in males of both species, and also in P. interpunctella females. E. cautella females showed no antennal activity in response to ethyl vanillin. All three volatiles were attractive to E. cautella males and P. interpunctella females in a flight tunnel. E. cautella females were significantly attracted only to ethyl vanillin. P. interpunctella males were attracted to PAA. Ethyl vanillin is a novel insect attractant, whereas both nonanal and phenylacetaldehyde mediate behavior in many insect species. A final experiment revealed that a blend of the three volatiles was required to induce landing in the flight tunnel bioassay, and that the landing rate was dependent on dose. The three-component blend attracted both sexes of P. interpunctella and females of E. cautella, whereas E. cautella males were not attracted.

Effect of Age on Eag Response and Attraction of FemaleAnastrepha suspensa(Diptera: Tephritidae) to Ammonia and Carbon Dioxide

Current ammonia-based lures vary considerably in their ability to attract Anastrepha fruit flies in the field. This report presents results from electroantennography (EAG) and behavioral bioassays that examined the effect of age on fly response to ammonia and carbon dioxide, two volatile chemicals released from commercial ammonium bicarbonate lures. EAG measurements from female Caribbean fruit flies, Anastrepha suspensa (Loew), showed that ammonia generated a greater EAG response in sexually immature females compared with mature females. Conversely, carbon dioxide elicited stronger EAG responses in sexually mature females. In flight tunnel bioassays, females from both age groups were captured in response to ammonia ranging from 60 to 3840 μg/h, but captures declined with increasing ammonia concentration. In bioassays with the two highest ammonia release rates, captures of immature females were significantly lower than captures of mature females. Carbon dioxide, ranging from 300 to 7200 μg/h, did not capture any flies when presented alone in the flight tunnel bioassay. However, for sexually mature flies, carbon dioxide in combination with ammonia was more attractive than ammonia alone. These age-related differences in response to ammonia and carbon dioxide may account for some of the variability observed in field tests with ammonium bicarbonate lures.

Plasticity in central olfactory processing and pheromone blend discrimination following interspecies antennal imaginal disc transplantation

The antennal imaginal disc was transplanted between premetamorphic male larvae of two different Lepidopteran moth species. Following adult eclosion, electrophysiological recordings were made from 33 central olfactory neurons in the antennal lobes of both Helicoverpa zea donor to Heliothis virescens recipient (Z-V) and reciprocal (V-Z) transplants. Under the influence of sensory neuron input derived from the transplanted antennal imaginal disc, most antennal lobe projection neurons (29/33) were classified as belonging to physiological categories encountered previously in donor species males. Furthermore, when stained many of these neurons had dendritic arbors restricted to donor-induced glomerular locations predicted by their physiology. However, some neurons with unexpected physiological profiles were also identified (4/33), but only in V-Z transplants. These profiles help to explain why some V-Z bilateral transplants were able to respond to both pheromone blends in flight tunnel bioassays, an unforeseen result counter to the assumption that a donor antenna develops a normal donor antennal olfactory receptor neuron complement. Stainings of several neurons in V-Z transplant males also revealed unusual morphological features including multiglomerular dendritic arbors and "incorrect" glomerular locations. These results indicate a developmental plasticity in the final dendritic arborization pattern of central olfactory neurons, including an ability to colonize and integrate inputs across topographically novel donor glomeruli, different from those found in the normal recipient antennal lobe.

Identification of host fruit volatiles from hawthorn (Crataegus spp.) attractive to hawthorn-origin Rhagoletis pomonella flies.

Solid-phase microextraction (SPME) and gas chromatography coupled with electroantennographic detection (GC-EAD) were used to identify volatile compounds from hawthorn fruit (Crataegus spp.) acting as behavioral attractants for hawthorn-infesting Rhagoletis pomonella flies. Consistent EAD activity was obtained for six chemicals: ethyl acetate (94.3%), 3-methylbutan-1-ol (4.0%), isoamyl acetate (1.5%), 4,8-dimethyl-1,3(E),7-nonatriene (0.07%), butyl hexanoate (0.01%), and dihydro-beta-ionone (0.10%). In a flight-tunnel bioassay, there was a dose-related increase in the percentage of flies flying upwind to the six-component mixture. Hawthorn-origin flies also made equivalent levels of upwind flight with the synthetic blend and an adsorbent extract of volatiles collected from whole fruit, each containing the same amount of the 3-methylbutan-1-ol compound. Significantly lower levels of upwind flight occurred to a previously identified volatile blend of ester compounds that attracts R. pomonella flies infesting domestic apples, compared with the hawthorn volatile mix. Selected subtraction assays showed further that the four-component mixture of 3-methylbutan-1-ol, 4,8-dimethyl-1,3(E),7-nonatriene, butyl hexanoate, and dihydro-beta-ionone also elicited levels of upwind flight equivalent to the six-component mix. Removal of 3-methylbutan-1-ol from the four-component blend resulted in complete loss of upwind flight behavior. Removal of dihydro-beta-ionone, 4,8-dimethyl-1,3(E),7-nonatriene, or butyl hexanoate from the four-component mixture resulted in significant decreases in the mean number of upwind flights compared to the four- or six-component mixtures.

Responses of Diadegma insulare (Hymenoptera: Ichneumonidae) to Caterpillar Feeding in a Flight Tunnel

A flight tunnel bioassay was used to evaluate attraction responses of female Diadegma insulare (Cresson), a host-specific parasitoid of the diamondback moth, Plutella xylostella (L.), to collard plants (Brassica oleracea var. acephala L.) infested with host and nonhost caterpillars. Adult female wasps showed increased responses to odors of the plant-host complex after a brief contact experience with host-infested collard leaves. Such an increase shows evidence of associative learning in this parasitoid to the odor released from the larval-plant complex. The same experimental design was also used to determine responses of the parasitoid to plants infested with nonhost larvae-cabbage looper, Trichoplusia ni (Hübner), and imported cabbageworm, Pieris rapae (L.). The female wasps conditioned to the plants infested with host larvae also showed increased responses to plants infested with larvae of cabbage looper or imported cabbageworm. These results indicate that plants damaged by host and nonhost caterpillars may release general odors that are attractive to D. insulare. The general damage odors caused by host and nonhost larval feeding may enhance biological control of the diamondback moth. Host-search ability of the parasitoid increases after experiencing host damage. When host populations are low in fields, plant odors caused by generalist herbivore feeding may also attract D. insulare parasitoids to the vicinity, thereby improving encounter chances of the parasitoid encountering diamondback moth larvae.

Minor and Intermediate Components Enhance Attraction of Female Mediterranean Fruit Flies to Natural Male Odor Pheromone and Its Synthetic Major Components

The attraction of virgin female medflies to either the natural pheromonal odor of calling males or its synthetic major components was enhanced by both intermediate and minor pheromonal components in multiple choice discrimination tests. The modification of the standard Gow rotating-trap-array, cage olfactometer to allow a single source of natural pheromonal odor to be delivered equally and simultaneously to a number of traps greatly increased trapping efficacy (64% capture rate) and ability to resolve odor preference discrimination by female flies. In olfactometer cage bioassays, responding female medflies expressed preferences in attraction to male odor augmented with either synthetic intermediate or minor components over male odor alone. In dual-choice flight-tunnel bioassays, the minor blend enhanced the attractiveness of both the natural male odor and its synthetic major components. Moreover, the minor blend, when presented together with the synthetic major components, comprised an artificial pheromonal lure competitive for the first time with the natural male odor in attraction of virgin female medflies.

Attraction of Anastrepha suspensa (Diptera: Tephritidae) to Volatiles from Avian Fecal Material

Flight tunnel bioassays confirmed attraction of female Caribbean fruit flies, Anastrepha suspensa (Loew), to volatiles from aqueous solutions of avian fecal material and methanol extracts of avian fecal material. Attraction was highest to freshly prepared and 72-h-old solutions of crude material. In direct comparisons between aqueous solutions of crude material and weight-equivalent amounts of methanol extract, more females were captured in response to volatiles from crude material in tests of 0-, 24- and 72-h-old solutions. Ammonia release rate was greater from the crude material than from the methanol extract in tests of 0-, 24- and 48-h-old solutions, The greatest amount (? sd) of ammonia was released from freshly prepared aqueous solutions of crude material (777 ? 250 .tg/h from 75 mg of crude material) but dropped within 24 h (288 ? 96 jtg/h from 75 mg of crude material) and then stayed close to that level. The greatest amount of ammonia released from methanol extracts was obtained from freshly prepared solutions (229 ? 70 pg/h from 75 mg crude material weight equivalent), also dropped within 24 h (98 ? 12 jg/h from 75 mg crude material weight equivalent) and then stayed fairly constant. Numbers of flies captured by either solution were directly correlated with ammonia release within the first 48 h of testing only, indicating that ammonia was partially or wholly responsible for attraction to the crude material during the first 48 h of testing. An increase in capture of females by volatiles from avian fecal material after 72 h in aqueous solution, which was observed in all tests, indicates that some chemical(s), other than ammonia, remain to be identified that are involved in fruit fly attraction.

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.

Effects of mating and accessory gland injections on olfactory-mediated behavior in the female mediterranean fruit fly, Ceratitis capitata

The female Mediterranean fruit fly, Ceratitis capitata, exhibits a preferential switch in certain olfactory-mediated behaviors as a result of mating. Unmated, laboratory-reared, virgin females chose the odor of male-produced pheromone over host fruit odor (guava) in a dual-choice flight tunnel bioassay. Females continued to preferentially respond to the male pheromone for several weeks if not allowed to mate. Mated females chose the host fruit odor over the male-produced pheromone and deposited significantly greater amounts of fertile eggs if given the opportunity. Virgin females injected with accessory gland fluid (AGF) from sexually mature males will “switch” their response from choosing the pheromone odor to choosing host fruit odor in the flight tunnel bioassay and exhibit egg-laying behavior typical of mated females. Significant differences in the number of female landings, time on the source (sphere) and number of eggs laid occurred when females were injected with AGF levels of 0.2 male equivalents or greater. Thus AGFs associated with sexually mature males contain factors that appear to influence olfactory-mediated flight behavior.

Identification and synthesis of female sex pheromone of Oriental beetle,Anomala orientalis (Coleoptera: Scarabaeidae)

Females of the Oriental beetle,Anomala orientalis (Waterhouse), release a sex pheromone composed of a 9:1 blend of (Z)- and (E)-7-tetradecen-2-one. The double-bond position of the pheromone was determined by DMDS derivatization and interpretation of the fragmentation patterns produced by monounsaturated ketones. In a sustained-flight tunnel, males responded by flying toward female beetles and attempting to copulate with them. Both effluvium and whole-body extracts of OB females were analyzed, and the activity was found only in the airborne extracts. Flight-tunnel bioassays also showed that a synthetic 90:10Z/E blend on a rubber septum was attractive and that the responses of males to this blend were equivalent toZ isomer alone, but much better than to the singleE isomer.

Role of plant volatiles in host location by the specialist parasitoidMicroplitis croceipes cresson (Braconidae: Hymenoptera)

A study was conducted to determine the primary source of volatile cues within the plant-host complex used by hostseeking freeflying female Microplitis cro-ceipesCresson in flight tunnel bioassays. In single-source and two-choice tests, using wasps given an oviposition experience on either cotton (Gossypium hirsutum)or cowpea (Vigna unguiculata)seedlings damaged by corn earworm (CEW; Helicoverpa zeaBoddie), the damaged seedlings were significantly more attractive than the CEW frass, which was in turn more attractive than the larvae themselves. In a series of two-choice wind-tunnel tests, the discriminatory ability of the wasps was examined, following various oviposition experiences. Significantly more wasps flew to plants with “old” damage than to plants with “fresh” damage, regardless of whether they had experience on fresh or old damage. In a comparison of plant species, wasps with only one experience on either hostdamaged cotton or host-damaged cowpea were unable to distinguish between them, and showed no preference for either plant, whereas wasps with multiple experiences on a particular plant preferentially flew to that plant in the choice test. In comparing hosts with nonhosts, wasps successfully learned to distinguish CEW from beet armyworm (BAW; Spodoptera exigua)on cotton but were unable to distinguish CEW from either BAW or cabbage looper (Trichoplusia ni)on cowpea. The results show the important role played by plant volatiles in the location of hosts by M. croceipesand indicate the wasps’ limitations in discriminating among the various odors. The ecological advantages and disadvantages of this behavior are discussed.