Diel Rhythms in Monochamus (Coleoptera: Cerambycidae): Production of and Response to a Male-Produced Aggregation Pheromone.

Recent research has shown that several species in the genus Monochamus, including Monochamus scutellatus scutellatus (Say) and Monochamus notatus (Drury), a close congener, are attracted to an aggregation pheromone, monochamol, but only M. s. scutellatus produces it. Investigations were conducted to determine if there is a diel rhythm in production of monochamol or response to monochamol + host attractants in field trials by M. s. scutellatus and M. notatus to prevent cross attraction with each other. Volatiles were collected from males and females of M. s. scutellatus and M. notatus every 8 h and analyzed by coupled gas chromatography-mass spectrometry. Traps baited with monochamol and the host volatiles α-pinene and ethanol were checked every 8 h in field tests. Only male M. s. scutellatus produced the pheromone, and did so in similar quantities during each 8-h time interval assessed, suggesting there is no diel rhythm in pheromone production. In field tests conducted in early to mid-July, significantly more M. s. scutellatus were captured during morning hours, and significantly more M. notatus were caught during afternoon or early evening hours, suggesting temporal partitioning of flight or in their response to the pheromone lures when both species are present. A temporal switch occurred later in the seasonal flight period (mid-August) when densities of M. s. scutellatus were low; all M. notatus and only one M. s. scutellatus were caught during morning hours. This suggests a temporal separation in mate location behavior when both species are abundant and using the same host to avoid interspecific mating.

Field Response of Monochamus scutellatus scutellatus and Monochamus notatus (Coleoptera: Cerambycidae) to the Male-Produced Pheromone, 2-(Undecyloxy)-Ethanol, and Host Volatiles.

Monochamus scutellatus scutellatus (Say) and Monochamus notatus (Drury) are pests of pines due to their ability to vector pinewood nematode, the causal agent of pine wilt disease. Several species of the genus Monochamus use the male-produced aggregation pheromone monochamol, which could potentially be an important component of lures for monitoring these species. In this study, investigations were conducted to determine if traps baited with monochamol were more attractive to male and female M. s. scutellatus and M. notatus with addition of two host volatiles, α-pinene and ethanol. In field tests, traps baited with monochamol + α-pinene or monochamol + α-pinene + ethanol caught significantly more M. s. scutellatus and M. notatus than either controls or monochamol alone. The mean female to male sex ratios of captured beetles increased with the addition of monochamol to α-pinene or α-pinene + ethanol for M. s. scutellatus , but only increased for M. notatus when added to α-pinene + ethanol. These results indicate monochamol can be utilized in formulating highly attractive lures with host volatiles for detection and monitoring of these species.

Identification of a male-produced aggregation pheromone for Monochamus scutellatus scutellatus and an attractant for the congener Monochamus notatus (Coleoptera: Cerambycidae).

We report identification and field testing of 2-(undecyloxy)-ethanol (monochamol) as a sex-specific, aggregation pheromone component produced by males of Monochamus scutellatus scutellatus (Say) (Coleoptera: Cerambycidae), a longhorned beetle native to North America. A congener, Monochamus notatus (Drury), which uses the same hosts as M. s. scutellatus, also was attracted to this compound in field trials, suggesting it may be a pheromone component for this species as well. Panel traps were deployed along transects at each of five field sites in May 2010 to test attraction of native beetle species to a suite of cerambycid pheromone components, including monochamol, 3-hydroxyhexan-2-one, (2R*,3R*)- and (2R*, 3S*)-2,3-hexanediol, racemic (E/Z)-fuscumol, and (E/Z)-fuscumol acetate. In total, 209 adult M. s. scutellatus (136 females, 73 males) and 20 M. notatus (16 females, four males) were captured, of which 86 and 70%, respectively, were captured in traps baited with monochamol (means significantly different). Analysis of headspace volatiles from adult M. s. scutellatus by coupled gas chromatography-mass spectrometry and gas chromatography-electroantennogram detection confirmed that monochamol was produced only by males. Monochamol was not found in headspace extracts from adult M. notatus. This study provides further evidence that monochamol is a pheromone component common to several species in the genus Monochamus. The pheromone component should prove useful for monitoring native species for management purposes or conservation efforts, and for quarantine monitoring for exotic species.

Repeatability of female response to ipsdienol enantiomeric mixtures by pine engraver,Ips pini (Coleoptera: Scolytidae).

Repeatability, a measure of the proportion of variance in a character that occurs among rather than within individuals, is assessed for the phenotypic trait of female response preference for enantiomeric blends of ipsdienol inIps pini at two pheromone concentrations-1 µg and 5 µg of ipsdienol. Average female response shows greater repeatability at the higher pheromone dosage when females are tested in two successive sets of five assays than when assayed in three successive sets or at the lower dosage. Repeatability within each set of five assays is highest for the first set and decreases thereafter. Thus the response phenotype of females for enantiomeric blends of ipsdienol in this experiment is context dependent; female choice of an enantiomeric blend differed between dosages and among sets of assays.

The role of lanierone in the chemical ecology ofIps pini (Coleoptera: Scolytidae) in California.

Five doses of lanierone (2-hydroxy-4,4,6-trimethyl-2,5-cyclohexadien-1-one) were tested with one dose of enantiomerically pure [99.4% (4R)-(-)] ipsdienol (2-methyl-6-methylene-2,7-octadien-4-ol) for activity as an aggregation pheromone ofIps pini (Say) in California. The response ofI. pini to 1 mg/day ipsdienol + 20 µg/day lanierone was significantly greater than the response to ipsdienol alone, but the response pattern did not demonstrate a clear dose-response relationship. The response to the highest dose of lanierone (2 mg/day) was significantly lower than the response to ipsdienol alone. Ipsdienol attracted significantly moreI. pini than a male-infested log. Lanierone did not alter the percentage of maleI. pini responding to ipsdienol alone. Neither sex ofI. pini orDendroctonus brevicomis LeConte from California produced detectable amounts of lanierone, but myrcene-aerated maleD. brevicomis produced 97.8%-(4S)-(+)-ipsdienol. The black-bellied clerid,Enoclerus lecontei (Wolcott) (Coleoptera: Cleridae) was attracted to lanierone when released with ipsdienol. Neither compound was attractive when released alone, proving synergism for the kairomone of this predator. Lanierone did not influence the response of the predatorsTemnochila chlorodia (Mannerheim) (Coleoptera: Trogositidae) andEnoclerus sphegeus (F.) (Coleoptera: Cleridae), which were attracted to all treatments containing ipsdienol.Tomicobia tibialis Ashmead (Hymenoptera: Pteromalidae) responded in significantly greater numbers to the male-infested log than it did to ipsdienol or ipsdienol + 20 µg/day lanierone.

Seasonal variability in response ofIps pini (Coleoptera: Scolytidae) to ipsdienol in New York.

In May,Ips pini in New York did not respond in the field to 50-98.5% (R)-(-)-ipsdienol (synthetic). In September, beetles responded strongly to 50-60% (R)-(-)-ipsdienol (synthetic). In May and June, New York beetles showed marked preference for their own males over Arizona males, which produce an average of 94.1% (R)-(-)-ipsdienol. This suggested that ipsdienol stereochemistry alone does not ensure activity and that an additional compound is necessary for attraction in May. In the second year of field tests, attraction to synthetic ipsdienol and male beetles was tested in the spring, summer, and fall. There was response only to males in the spring and mid-summer and to both males and synthetic ipsdienol in the late summer and fall, causing a significant treatment x sampling period (date) interaction. Laboratory-reared beetles were not significantly more attracted to ipsdienol than to a blank airstream in laboratory assays, while male volatiles were significantly more attractive than ipsdienol and the blank. These data demonstrate that there is one or more unknown semiochemicals necessary for pheromonal response and that the behavioral activity of synthetic ipsdienol varies seasonally.

Lanierone: A new pheromone component fromIps pini (Coleoptera: Scolytidae) in New York.

A new pheromone component, lanierone, (2-hydroxy-4,4,6-trimethyl-2,5-cyclohexadien-1-one) was isolated and identified from a Porapak Q collection of volatiles from maleIps pini from New York through GC fractionation, bioassay, and spectrometry. In both the laboratory and the field, synthetic lanierone, in a 1:100 ratio with synthetic ipsdienol, is as attractive as natural pheromone sources. Synthetic ipsdienol alone is not attractive in the laboratory and only weakly attractive in the field. Varying the ratio of lanierone to ipsdienol in the field from 10(-4)∶1 to 1∶1 in 10-fold increments resulted in an increased number of beetles trapped at the three lower ratios, but also in an increase in the proportion of males trapped. In the field, all combinations of lanierone to ipsdienol attracted proportionately fewer males than did pheromone-producing male beetles. GC and GC-MS analyses of Porapak Q-trapped volatiles revealed that lanierone is produced in an amount equal to about 0.2% of that of ipsdienol and is produced exclusively by males. The small amount of lanierone produced, together with a GC retention time similar to that of ipsdienol on a nonpolar column, probably confounded its detection in earlier studies.