John H. Borden

A review of the chemical ecology of the Cerambycidae (Coleoptera)

Summary.This review summarizes the literature related to the chemical ecology of the Cerambycidae and provides a brief overview of cerambycid biology, ecology, economic significance, and management. Beetles in the family Cerambycidae have assumed increasing prominence as pests of forest and shade trees, shrubs, and raw wood products, and as vectors of tree diseases. Exotic species associated with solid wood packing materials have been notable tree killers in North American urban and peri-urban forests. In forested ecosystems native species respond to disturbances such as fires and windstorms, and initiate the biodeterioration of woody tissue. Eggs are laid by females, on or through the bark surface of stem and branch tissue of moribund, recently killed or decomposing woody plants; larval cerambycids (roundheaded woodborers) typically feed in the phloem and later in the xylem. Females will also, in some cases, select living hosts, e.g. adult conifer and angiosperm trees, for oviposition. Research on the chemical ecology of over 70 species has revealed many examples of attractive kairomones (such as floral volatiles, smoke volatiles, trunk and leaf volatiles, and bark beetle pheromones), repellents and deterrents, oviposition stimulants, short- and long-range sex pheromones, and defensive substances. Emerging generalities are that attractants tend to be monoterpenoids and phenolic esters; oviposition stimulants are monoterpenoids and flavanoids; short-range sex pheromones are female-produced, methyl-branched cuticular hydrocarbons; and long-range sex pheromones are male-produced α-hydroxy ketones and (α,β)-diols ranging in length from 6 to 10 carbons. The latter compounds appear to originate from glands in the male thorax; putative defensive substances originate from metasternal secretory pores or mandibular glands. In one unusual case, a flightless, subterranean female that attacks sugar cane produces a sex pheromone that is derived from the amino acid isoleucine. With significantly more than 35,000 species of Cerambycidae worldwide, these generalities will be subject to change as more species are examined.

Synergistic Blends of Monoterpenes for Aggregation Pheromones of the Mountain Pine Beetle (Coleoptera: Curculionidae)

Abstract The superiority of the host monoterpene myrcene as a synergist for trans-verbenol and exo-brevicomin, aggregation pheromone components of the mountain pine beetle, Dendroctonus ponderosae Hopkins (Coleoptera: Curculionidae), suggests that the ancestral host of the mountain pine beetle is a pine rich in myrcene. A field trapping experiment in British Columbia testing reconstituted bole oleoresin of whitebark pine, Pinus albicaulis Engelmann, composed of mainly myrcene (20.7%), terpinolene (6.8%), and 3-carene (61.9%) showed it to be a better pheromone synergist than reconstituted bole oleoresin of lodgepole pine, Pinus contorta variety latifolia Engelmann, which contained only 2.7, 1.0, and 6.0%, respectively, of the above-mentioned three compounds. In the same experiment myrcene alone was the best synergist. In subsequent experiments, testing myrcene, terpinolene and 3-carene alone and in all possible binary and ternary combinations, a 50:50 blend of myrcene and terpinolene released at the same rate as either compound alone generally resulted in trap catches ≈3 times higher than with myrcene as a synergist. This result held as long as the terpinolene was free of contaminants, and the traps were in the open, well away from potential interference of semiochemicals emitted by newly attacked trees. 3-Carene seemed to be inert or slightly inhibitory. No single monoterpene tested alone or in binary or ternary combination in the absence of pheromones was attractive. There was no effect of doubling or tripling the release rate of myrcene or terpinolene. In five of nine experiments, adding terpinolene to myrcene caused a significant increase in the percentage of female mountain pine beetles captured. Among host pines, the presence of highly synergistic monoterpenes at various levels in combination with other monoterpenes that are apparently either inert or inhibitory could account for different degrees of pheromone synergism, and thus host preference. The highly synergistic effect of combining myrcene plus terpinolene with the mountain pine beetle aggregation pheromone components opens up the potential for suppression of populations through semiochemical-based mass trapping.

Close-range, in-flight integration of olfactory and visual information by a host-seeking bark beetle

A long‐standing controversy questions whether foraging bark beetles assess the suitability of individual host trees using cues at close range while flying or engage in random landing followed by contact assessment. In most cases, visual discrimination mechanisms are ignored. We show that pheromone‐responding mountain pine beetles (MPB), Dendroctonus ponderosae Hopkins (Coleoptera: Scolytidae), can visually discriminate between ‘host’ (black) and ‘non‐host’ (white) traps arranged in small clusters, in the absence of additional host olfactory information, and that males (but not females) demonstrate a greater preference for combined host visual and olfactory cues. However, white, non‐host traps baited with a host volatile were as attractive as unbaited, black host traps. Our results support the hypotheses that when deciding to land, the MPBs integrate visual and olfactory information and can process cues in both sensory modes at relatively close range (≤2 m). Thus, host selection mechanisms in this species are unlikely to be random with respect to either sensory mode.

Dose-Dependent Pheromone Responses of Mountain Pine Beetle in Stands of Lodgepole Pine

Abstract We conducted seven behavioral choice tests with Lindgren multiple-funnel traps in stands of mature lodgepole pine in British Columbia, from 1988 to 1994, to determine the dose-dependent responses of the mountain pine beetle, Dendroctonus ponderosae Hopkins, to its pheromones. A multifunctional dose-dependent response was exhibited by D. ponderosae to the pheromones cis- and trans-verbenol in areas with low population numbers. In an area with a high population level of D. ponderosae, the response was directly proportional to release rates. No dose-dependent response was exhibited by D. ponderosae to exo-brevicomin at low release rates. At rates of release >0.5 mg/d, exo-brevicomin interrupted the attraction of D. ponderosae in a dose-dependent fashion. The bark beetle predators, Enoclerus sphegeus (F.) and Thanasimus undatulus (Say), showed dose-dependent responses to only a few pheromones, with trap catches directly proportional to release rates. The multi-functional response of D. ponderosae to verbenols is consistent with an optimal attack density hypothesis.

Efficacy of “Verbenone Plus” for Protecting Ponderosa Pine Trees and Stands From Dendroctonus brevicomis (Coleoptera: Curculionidae) Attack in British Columbia and California

ABSTRACT The western pine beetle, Dendroctonus brevicomis LeConte (Coleoptera: Curculionidae, Scolytinae), is a major cause of ponderosa pine, Pinus ponderosa Douglas ex Lawson, mortality in much of western North America. We review several years of research that led to the identification of Verbenone Plus, a novel four-component semiochemcial blend [acetophenone, (E)2-hexen-1-ol + (Z)-2-hexen-1-ol, and (-)-verbenone] that inhibits the response of D. brevicomis to attractant-baited traps, and examine the efficacy of Verbenone Plus for protecting individual trees and forest stands from D. brevicomis infestations in British Columbia and California. In all experiments, semiochemicals were stapled around the bole of treated trees at ≈2 m in height. (-)-Verbenone alone had no effect on the density of total attacks and successful attacks by D. brevicomis on attractant-baited P. ponderosa, but significantly increased the percentage of pitchouts (unsuccessful D. brevicomis attacks). Verbenone Plus significantly reduced the density of D. brevicomis total attacks and D. brevicomis successful attacks on individual trees. A significantly higher percentage of pitchouts occurred on Verbenone Plus-treated trees. The application of Verbenone Plus to attractant-baited P. ponderosa significantly reduced levels of tree mortality. In stand protection studies, Verbenone Plus significantly reduced the percentage of trees mass attacked by D. brevicomis in one study, but in a second study no significant treatment effect was observed. Future research should concentrate on determining optimal release rates and spacings of release devices in stand protection studies, and expansion of Verbenone Plus into other systems where verbenone alone has not provided adequate levels of tree protection.

A New Trap and Lure for Drosophila melanogaster (Diptera: Drosophilidae)

ABSTRACT We conducted a series of nine laboratory experiments testing the response of “vinegar flies,” Drosophila melanogaster Meigen (Diptera: Drosophilidae), released in bioassay chambers to experimental traps and lures. These experiments showed that an effective trap could be constructed from a clear 225-ml screw-cap jar fitted with a hollow 8-mm-diameter cylindrical cross bridge. Flies could enter the trap from either end of the cylindrical “gate” and in turn could enter the interior chamber of the trap through a cut out portion at mid-span of the cylinder. The experiments also showed that a natural-component lure could be made using a teabag containing freeze-dried banana powder, yeast, and carrageenan gum powder as a humectant. When dipped in water for 10–15 s and then placed in the bottom of a trap, the teabag provided effective attraction for at least 7 d. Captured flies were immobilized on a sticky card placed in the trap, allowing them to be easily seen. Unlike other traps that cannot be opened and have liquid lures, the cylindrical-gate trap can be reused repeatedly if the teabag and sticky card are replaced. A final two experiments showed that the prototype operational cylindrical-gate trap with a teabag lure captured 3.3 and 2.3 times more released flies, respectively, than the next best of three commercially available traps.

Dose-Dependent Pheromone Responses of Ips pini, Orthotomicus latidens (Coleoptera: Scolytidae), and Associates in Stands of Lodgepole Pine

Abstract We conducted four behavioral choice tests in stands of mature lodgepole pine in British Columbia, from 1988 to 1991, to determine the dose-dependent responses of Orthotomicus latidens (LeConte) and Ips pini (Say) to their respective pheromones. Dose-dependent responses were exhibited by I. pini to (±)-ipsdienol and lanierone, with trap catches directly proportional to pheromone release rates. We found differences in sex ratio of I. pini in their responses to ipsdienol but not lanierone. There was no dose-dependent response exhibited by O. latidens to its pheromone, (±)-ipsenol, with or without the presence of the host kairomone, (−)-β-phellandrene. The bark beetle predator, Enoclerus lecontei (Wolcott), showed a dose-dependent response to lanierone. Thanasimus undatulus (Say) was attracted to ipsenol in a dose-dependent fashion only when traps were also baited with β-phellandrene. Neither T. undatulus nor E. sphegeus (F.) exhibited dose-dependent responses to ipsdienol.

Stabilized synthetic brood pheromone delivered in a slow-release device enhances foraging and population size of honey bee, Apis mellifera, colonies

Summary The 10-component honey bee brood pheromone has considerable potential for use in honey bee management now that durable stability has been obtained by adding a food-grade antioxidant. Practical applications require, however, that a long-term slow release device be developed and tested. After discarding 19 potential materials and devices for releasing synthetic brood pheromone, we found a suitable method using a small plastic pouch with a pheromone impermeable Mylar backing and a pheromone-permeable low-density polyethylene release surface. Heat-sealed pouches, 3.8 × 3.5 cm, containing 200 μl of synthetic brood pheromone released 0.30–0.35 mg of pheromone per day in the laboratory; pheromone had to be artificially removed from the polyethylene membrane daily (equivalent to being removed by contact with worker bees) in order for the flow to be maintained. Compared to untreated control colonies, colonies exposed from late summer to early fall in southeast Texas to pheromone-laden pouches mounted in 35 mm plastic slide frames demonstrated more frequent foraging trips by worker bees, heavier pollen loads, and a higher ratio of pollen to non-pollen foragers from days 8–36 of continuous exposure. Pheromone-treated colonies also had significant growth in brood comb area and adult population level at a time when untreated control colonies were naturally declining in size.

Olfactory and Feeding Preferences of Cryptorhynchus lapathi L. (Coleoptera: Curculionidae) Among Hybrid Clones and Natural Poplars

Abstract Hybrid poplar clones show varying levels of attack by Cryptorhynchus lapathi (L.), a wood-boring weevil. We studied differences in olfactory and feeding behavior among four different hybrid poplars in a series of laboratory bioassays. Weevils did not discriminate between resistant and susceptible clones based on olfaction in pitfall bioassays or antennal responses but did discriminate against the most resistant hybrid, NM 6 (P. nigra L. × P. maximowiczii Henry), in choice and no-choice paired-twig feeding bioassays. In addition, the susceptible hybrid, TN 302–9 (P. trichocarpa Torrey and Gray × P. nigra), was preferred for feeding over Salix scouleriana Barratt ex Hooker, a preferred host in the wild. We conclude that resistance among hybrid poplars is in part based on antixenotic cues before oviposition.

Treatment with Synthetic Brood Pheromone (SuperBoost) Enhances Honey Production and Improves Overwintering Survival of Package Honey Bee (Hymenoptera: Apidae) Colonies

ABSTRACT We evaluated a year-long treatment regime testing synthetic, 10-component, honey bee, Apis mellifera L. (Hymenoptera: Apidae), brood pheromone (SuperBoost; Contech Enterprises Inc., Delta, BC, Canada) on the productivity and vigor of package bee colonies in the lower Fraser Valley of British Columbia, Canada. Fifty-eight newlyestablished 1.3-kg (3-lb) colonies treated three times with SuperBoost at 5-wk intervals starting 30 April 2009 were compared with 52 untreated control colonies. Treated colonies produced 84.3% more honey than untreated control colonies. By 8 September 2009, SuperBoost-treated colonies had 35.4% more adults than untreated colonies. By 28 September, net survival of treated and control colonies was 72.4 and 67.3%, respectively. On 5 October, treated and control colonies were divided into two additional groups, making up four cohorts: SuperBoost-treated colonies treated again during fall and spring build-up feeding with pollen substitute diet (BeePro, Mann Lake Ltd., Hackensack, MN; TTT); controls that remained untreated throughout the year (CCC) ; colonies treated with SuperBoost in spring—summer 2009 but not treated thereafter (TCC); and original control colonies treated with SuperBoost during the fall and spring build-up feeding periods (CTT). There was no difference among cohorts in consumption of BeePro during fall feeding, but TTT colonies (including daughter colonies split off from parent colonies) consumed 50.8% more diet than CCC colonies during spring build-up feeding. By 21 April, the normalized percentages of the original number of colonies remaining (dead colonies partially offset by splits) were as follows: CCC, 31.4%; CTT, 43.8%; TCC, 53.59%; and TTT, 80.0%. The net benefit of placing 100 newly established package bee colonies on a year-long six-treatment regime with SuperBoost would be US