A pear-derived kairomone with pheromonal potency that attracts male and female codling moth, Cydia pomonella (L.).

Ethyl (2E, 4Z)-2,4-decadienoate, a pear-derived volatile, is a species-specific, durable, and highly potent attractant to the codling moth (CM), Cydia pomonella (L.), a serious pest of walnuts, apples, and pears worldwide. This kairomone attracts both CM males and virgin and mated females. It is highly attractive to CM in both walnut and apple orchard contexts, but has shown limited effectiveness in a pear orchard context. Rubber septa lures loaded with ethyl (2E, 4Z)-2,4-decadienoate remained attractive for several months under field conditions. At the same low microgram load rates on septa, the combined gender capture of CM in kairomone-baited traps was similar to the capture rate of males in traps baited with codlemone, the major sex pheromone component. The particular attribute of attracting CM females renders this kairomone a novel tool for monitoring population flight and mating-ovipositional status, and potentially a major new weapon for directly controlling CM populations.

Attractants from Bartlett pear for codling moth, Cydia pomonella (L.), larvae.

The alkyl ethyl and methyl esters of (2E,4Z)-2,4-decadienoic acid found in head-space samples of ripe Bartlett pear (Pyrus communis L.) stimulated a response from neonate larvae of the codling moth (CM), Cydia pomonella (L.), in both static-air Petri-plate and in upwind Y-tube and straight-tube olfactometer bioassays. In comparison with the known CM neonate attractant, (E,E)-alpha-farnesene, ethyl (2E,4Z)-2,4-decadienoate was attractive at 10-fold and 1,000-fold lower threshold dosages in the Petri-plate and in the Y-tube bioassays, respectively. Methyl (2E,4Z)-2,4-decadienoate was attractive to CM neonates in these bioassays at much higher doses than ethyl (2E,4Z)-2,4-decadienoate. Other principal head-space volatiles from ripe pear fruit and pear leaves, including butyl acetate, hexyl acetate, (Z)-3-hexenyl acetate, and (E)-beta-ocimene, were not attractive to CM neonates. The potential uses of these pear kairomones for monitoring and control of CM in walnuts and apple are discussed.

Volatile components of green walnut husks.

Volatiles were isolated from whole green mature walnuts (Hartley variety) with husks still intact using dynamic headspace sweeping with trapping on Tenax. A total of 45 volatile compounds were identified by GC-MS. Major volatiles identified included (E)-4, 8-dimethyl-1,3,7-nonatriene, pinocarvone, pinocarveol, myrtenal, myrtenol, (E,E)-4,8,12-trimethyl-1,3,7,11-tridecatetraene, caryophyllene epoxide, verbenol, verbenone, and terpinolene. Green walnuts that had been infested with codling moth showed appreciably higher amounts emitted for (E)-4,8-dimethyl-1,3,7-nonatriene, (E, E)-4,8,12-trimethyl-1,3,7,11-tridecatetraene, alpha- and beta-pinenes, sabinene, (E)-beta-ocimene, (E,E)-alpha-farnesene, and linalool. The infested nuts also emitted benzyl methyl ether, isobutyl cyanide, and 1-nitro-3-methylbutane, compounds not found with the healthy nuts. Volatiles from uninfested green walnuts at the maturity stage where the husk was just beginning to split were also analyzed and compared.

Electroantennogram responses ofHyles lineata (Sphingidae: Lepidoptera) to volatile compounds fromClarkia breweri (Onagraceae) and other moth-pollinated flowers.

Electroantennograms (EAGs) from field-collectedHyles lineata moths were recorded in response to 10 individual floral volatiles identified fromClarkia breweri (Onagraceae), to 22 scent compounds produced by other moth-pollinated flowers and to eight ubiquitous "green leaf volatiles." Females' EAGs were generally 1.5- to 2-fold greater than those observed for male moths. Female:male EAG rank orders were significantly correlated, but marked differences in order were observed for some compounds (e.g., benzyl alcohol, cinnamic aldehyde, geraniol, and linalool). Linalool, benzyl acetate, methyl salicylate, and pyranoid linalool oxide elicited the largest EAG responses (-1.2 to -0.8 mV) among scent compounds fromC. breweri. EAG responses were significantly lower for monoterpenes as a pooled compound class than for aromatic esters, alcohols and aldehydes, fatty acid derivatives, N-bearing compounds and oxygenated terpenoids. EAG responses to structurally related scent compounds were not significantly different in most cases. Both male and femaleH. lineata were sensitive to mostC. breweri scent compounds at 10(-2) to 10(-4) µg/µl doses, and rank order in potency varied with the dose/concentration tested.H. lineata's olfactory sensitivity to diverse volatile compounds across a range of doses/concentrations suggests that a broad array of volatiles could function as floral attractants for foraging hawkmoths.

Attraction of female mediterranean fruit flies to the five major components of male-produced pheromone in a laboratory flight tunnel.

Attraction and pheromonal activity of five major identified components of the male-produced sex pheromone of the Mediterranean fruit flyCeratitis capitata to virgin laboratory-reared females was assessed in a laboratory flight tunnel. Dual-choice competitive assays were run to establish a baseline response of virgin females to live male pheromone, individual components, and an ensemble of all five compounds alone (air control) and competitively against one another. Approximately 50% of the females released in the tunnel were captured on leaf models emitting pheromonal odors from five live males. Over 37% of released females responded to an ensemble of five major identified components presented in individual capillaries. Response of females to individual components was less than 10%. Competitive assays showed the live male-produced pheromone to be more attractive than either the five major component ensemble (FMCE) or individual components. Further research is likely to identify other male-produced compounds with pheromonal activity that could improve development of a pheromone-based trap for monitoring Mediterranean fruit fly populations.

Electroantennogram response of alfalfa seed chalcid,Bruchophagus roddi (Hymenoptera: Eurytomidae) to host- and nonhost-plant volatiles.

The alfalfa seed chalcid (ASC),Bruchophagus roddi, is a monophagous pest of alfalfa that parasitizes developing seeds. To further understand the olfactory basis of host-plant recognition by ASCs, we recorded electroantennograms (EAGs) from females and males to 39 volatiles from both alfalfa and red clover. The chemoreceptive sensitivity of ASCs was selective for certain general classes of compounds, defined by their carbon-chain length (C6 and C8), structure (aliphatics and phenolics), isomerism, and/or functional group (acetates, ketones, and alcohols). The compounds that elicited the largest EAGs were ranked as follows: (Z)-3-hexenyl acetate > hexyl acetate ≥ acetophenone ≥ octan-3-one ≥ methyl salicylate > octan-3-ol > oct-1-en-3-one > oct-1-en-3-ol ≥ (E)-ß-ocimene ≥ (Z)- and (E)-3-hexen-1-ols. Over half the test compounds elicited significantly different responses between the sexes, and female antennal responses exceeded those of males for twice the number of these volatiles. Relationships of the tested volatiles to host-plant composition, EAG responses, and ASC behaviors showed no consistent correlations. However, nearly all of the host-plant volatiles known to stimulate behavioral activity also elicited moderate to potent EAG responses.

Electroantennogram responses of mediterranean fruit fly,Ceratitis capitata (Diptera: Tephritidae) to trimedlure and itstrans isomers.

Electroantennograms (EAGs) of unmated laboratory-reared male and femaleCeratitis capitata (Wiedemann) were recorded in response to the attractant trimedlure [tert-butyl 4(and 5)-chloro-trans-2-methylcyclohexane-1-carboxylate] and its fourtrans isomers. For both sexes, the magnitude of the EAG response was relatively low as compared to other previously tested compounds (i.e., plant volatiles). Dosage-response curves generated for all TML isomers revealed that flies responded to increasing dosages over a relatively narrow range (two to three log steps). Responses for both sexes peaked at ca. 10 µg dose for all isomers. Antennal response in males was greatest to the C isomer followed by the B1, A, and B2 isomers, while responses of females were greatest for the A isomer followed by B1, C, and B2. Both sexes exhibited a long recovery period for the response potential to return to baseline at doses above 1 µg for all of the isomers tested, except for B2. The low EAG sensitivity to trimedlure and the apparent EAG selectivity to the C isomer in males are discussed in relation to the known field attractancy of males to the C, A, B1, and B2 isomers.

Electroantennogram responses of the mediterranean fruit fly,Ceratitis capitata, to a spectrum of plant volatiles.

Electroantennograms (EAGs) were recorded from unmated, laboratory-reared, male and femaleCeratitis capitata (medfly) in response to a range of C1 and C2 to C12 carbon chain-length aliphatic alcohols, aldehydes, acetates, and acids, and lactones, some of which are known volatiles from leaves and fruits. A large degree of EAG response uniformity between the sexes was observed, with only eight of the 70 compounds tested eliciting significantly larger amplitude EAG responses from female than male antennae. In general, for the five functional-group series tested, aldehydes and alcohols elicited greater responses than acetates, lactones, and acids. The unsaturated alcohols, aldehydes, acetates, and acids elicited equal or larger amplitude EAG responses than their comparable saturated compounds. For four of the functional-group series tested, the EAG response amplitude was significantly greater for a particular carbon chain length, with responsiveness to primary alcohols and aldehydes peaking at C6, acids peaking at C5-6, and acetates peaking at both C5 and C8. The EAG responses to both the 2- and 3-position monoenic alcohols peaked at C6 and C8, while the secondary alcohols peaked at C7. The greatest EAG responses of all compounds tested were elicited by monoenic C6 alcohols and aldehydes that are constituents of the "general green-leaf odor" that emanates from most plants. The potential adaptive benefit of selective sensitivity to green-leaf volatiles is discussed in regard to foraging behavior of medflies.

Sensitivity of antennae of male and femaleIps paraconfusus (Coleoptera: Scolytidae) to their natural aggregation pheromone and its enantiomeric components.

Antennae of male and femaleIps paraconfusus were equally and highly sensitive to their male-produced, multicomponent aggregation pheromone. Female and male antennae were highly sensitive to the pheromonal component, (S)-(-)-ipsenol, but essentially insensitive to its antipode, (R)-(+)-ipsenol. Further, female and male antennae were more sensitive to the pheromonal component, (S)-cis-verbenol, than to its antipode, (R)-cis-verbenol. Dramatic sexual dimorphism in chiral sensitivity to the ipsdienol enantiortiers was found, with female antennae being more sensitive to the conspecific pheromonal enantiomer, (S)-(+)-ipsdienol, and male antennae being more sensitive to the antipode, (R)-(-)-ipsdienol. Since (R)-(-)-ipsdienol is the principal pheromone of CaliforniaIps pini and interruptsI. paraconfusus aggregation, male antennae appear to be more sensitive to an interspecific allomone than a conspecific pheromone. Of the conspecific pheromonal enantiomers, both male and female antennae were most sensitive to (S)-(+)-ipsdienol, intermediately sensitive to (S)-(-)-ipsenol, and least sensitive to (S)-cis-verbenol. However, when enantiomeric sensitivities were compared to the estimated concentrations of these components in the natural pheromone, (S)-(~)-ipsenol tended to equal or approach the potency of (S)-(+)-ipsdienol as an antennal stimulant, while antennal responsiveness to (S)-cis-verbenol was dramatically less than for the other two pheromonal components. The behavioral implications of such physiological sensitivities are discussed in regard to perception of multicomponent synergistic pheromones and the relative efficacy of each component as an orientation cue.

Sensitivity of antennae of male and femaleIps paraconfusus (Coleoptera: Scolytidae) to its pheromone and other behavior-modifying chemicals.

The antennal sensitivities of both male and femaleIps paraconfusus were found generally to be greatest for conspecific aggregation pheromones (ipsdienol, ipsenol); intermediate for an additional conspecific pheromone (cis-verbenol), an aggregation synergist (2-phenylethanol), and pheromones/allomones of sympatric species (trans-verbenol, verbenone, and frontalin); and lowest for both host terpenes (alpha-pinene and myrcene) and other bark beetle-produced odorants (exo-brevicomin and linalool). Of the enantiomeric compounds tested, antennae of both sexes did not differ in sensitivity between thetrans-verbenol enantiomers at low dosage levels; but at higher dosages, the conspecific-produced enantiomer, (1R,4S,5R)-(+)-trans-verbenol, elicited larger mean EAG responses than its antipode, (1S,4R, 5S)-(-)-trans-verbenol. At the mid-dosage range, female antennae tended to be slightly more responsive to (S)-(-)-verbenone than to (R)-(+)-verbenone, while male antennae were equally responsive to stimulations by either verbenone enantiomer. In field bioassays there was a large and significant reduction in trap catches ofI. paraconfusus on traps where the (S)-(-)- or (R)-(+)-enantiomers of verbenone were evaporated beside logs containing boring conspecific males. Only when the (S)-(-)-enantiomer of verbenone was evaporated beside logs containing boring males did the sex ratio ofI. paraconfusus trapped shift from female-dominated to male-dominated attraction. Thus both physiological and behavioral data suggest a differential chiral sensitivity of female beetles for the verbenone enantiomers. The relative sensitivities between different chiral compounds derived from one or the other of the common precursoral host terpenes, (S)-(-)- and (R)-(+)alpha-pinene or myrcene, are discussed.