R. E. Rice

Host-plant green-leaf volatiles synergize the synthetic sex pheromones of the corn earworm and codling moth (Lepidoptera).

SummaryThe capture of adult male moths in female sex pheromone traps of two key agricultural pests, the corn earworm (Helicoverpa zea) and the codling moth (Cydia pomonella), is enhanced or synergized by a certain group of host-plant volatiles, the “green-leaf volatiles” (GLVs). Since female adults of both species call and release their sex pheromones while perched upon the leaves of their host-plants, the volatile constituents from the leaves of a number of host-plants were compared. Sex pheromone traps containing one of the prominent leaf volatiles of certainH. zea hosts, (Z)-3-hexenyl acetate, not only significantly increased the capture ofH. zea males but were preferred over traps baited only with sex pheromone. Similarly, traps baited with synthetic sex pheromome ofC. pomonella plus a blend of GLVs captured significantly more males than traps baited only with sex pheromone. Since male moths are not captured in traps baited only with these GLVs, it appears that these GLVs act as pheromone synergists which increase or enhance the attraction or arrestment of male moths in pheromone traps.

Sex Attractant Pheromone of the Red-Shouldered Stink Bug Thyanta pallidovirens: A Pheromone Blend with Multiple Redundant Components

The male-produced sex pheromone of the red-shouldered stink bug, Thyanta pallidovirens (Stål) (Hemiptera: Pentatomidae) consists of a blend of methyl (E2,Z4,Z6)-decatrienoate (E2,Z4,Z6–10:COOMe), and the sesquiterpenes (+)α-curcumene, (−)-zingiberene, and (−) -β-sesquiphellandrene. In laboratory bioassays, sexually mature males attracted sexually mature females but not males, and females did not attract either sex. Extracts of volatiles collected from sexually mature males contained compounds not present in extracts from females or sexually immature males, and male-produced extract was attractive to females. Biological activity was lost when the extract was fractionated, indicating that the pheromone consisted of at least two components having different chemical properties. Individually, pheromone components were not attractive to females, but E2,Z4,Z6–10:COOMe in combination with at least one of the three male-produced sesquiterpenes was attractive. The presence of more than one sesquiterpene in the blend did not increase attraction, indicating redundancy in the pheromone signal. Male extract was as attractive as a blend reconstructed from synthesized compounds, indicating all biologically active components had been identified. In bioassays conducted at dusk in a 1- × 1- × 1-m screen field cage, females were attracted to synthetic pheromone lures. In field trials, adult female T. pallidovirens were attracted to pheromone-baited traps in relatively low numbers. The profile of volatiles released by sexually mature males of a congeneric species, Thyanta accerra custator McAtee, was remarkably similar to that of male T. pallidovirens, with the exception that the former species produced (E)-2-decenal, a compound that was not found in T. pallidovirens extracts.

Sex Pheromone of the Mirid Bug Phytocoris relativus

The sex attractant pheromone produced by adult females of the mirid bug Phytocoris retativus has been identified as a 2:1 blend of hexyl acetate with (E)-2-octenyl butyrate. The pheromone is stage-, sex-, and species-specific, attracting only adult male P. relativus. Hexyl acetate was identified in aeration extracts from both sexes, while (E)-2-octenyl butyrate was produced only by females. Both males and females also produced hexyl butyrate and octyl acetate, while only females produced (E)-2-hexenyl and octenyl acetates, and (Z)-3-octenyl acetate. The function(s) of these chemicals were not determined. Attraction of males increased with dose, with doses of 0.1 to 33 mg loaded on grey rubber septa. Attractiveness of rubber septum lures decreased quickly with age due to the volatility of the two pheromone components.

Male-produced sex attractant pheromone of the green stink bug, Acrosternum hilare (Say).

Sexually mature virgin adult males of the green stink bug, Acrosternum hilare attracted sexually mature virgin adult females in laboratory bioassays using a vertical Y-tube. There was no indication that males attracted other males, or that females attracted either sex. These results suggested that A. hilare males produce a sex pheromone. Extracts of odors collected from sexually mature males contained compounds that were not present in extracts from females or sexually immature males. (4S)-Cis-(Z)-bisabolene epoxide ((4S)-cis-Z-BAE) was the major sex-specific component of the extract. The crude extract was attractive to female A. hilare, but when separated into four fractions, only the portion containing (4S)-cis-Z-BAE and the minor component (4S)-trans-Z-BAE was attractive to females. This fraction was as attractive as the crude extract, suggesting that the former contained all the pheromone components. Neither synthetic (4S)-cis-Z-BAE nor (4S)-trans-Z-BAE alone was attractive to females, but a 95:5 cis:trans blend, mimicing the ratio naturally produced by males, was attractive to females in Y-tube bioassays. Bioassays in a field cage showed that significantly more A. hilare females were attracted to cotton string lures treated with 1 mg of a 95:5 blend of (4S)-cis-Z-BAE and (4S)-trans-Z-BAE placed inside a bouquet of alfalfa than to an alfalfa bouquet containing a pentane-treated control. In field cage studies, attraction of females was greatest during the late afternoon and evening hours, and female A. hilare approached the synthetic pheromone source almost exclusively by walking.

Synthesis and identification of a third component of the San Jose scale sex pheromone.

Two components of the San Jose scale sex pheromone had previously been identified as 7-methyl-3-methylene-7-octen-1-yl propanoate (I) and (Z)-3,7-dimethyl-2,7-octadien-1-yl propanoate (II). An isomer and various homologs have subsequently been synthesized and tested in a greenhouse bioassay. TheE isomer of II (XI) was found to be attractive to male scales. This compound has now been isolated and identified from airborne extracts of virgin female scales. The composition of the natural pheromone was 48.5%, 46.7%, and 4.8% of I, II, and XI, respectively. In field tests in California and New York, synthetic XI was found to be attractive to male scales alone and in combination with I and II, but there was no obvious increase in trap catch when the synthetic isomers were present in the same ratio as in the natural blend.

Sex pheromone of the San Jose scale

The sex pheromone of the San Jose scale,Quadraspidiotus perniciosus (Comstock), was isolated from airborne collections on Porapak Q. Two components, present in approximately equal amounts, were identified as (Z)-3,7-dimethyl-2,7-octadien-1-yl propanoate and 3-methylene-7-methyl-7-octen-1-yl propanoate. Greenhouse bioassays and field tests have shown that the compounds are independently attractive to male San Jose scale. These structures are compared with those of other known scale pheromones.