Volatile profile differences and the associated Sirex noctilio activity in two host tree species in the Northeastern United States.

Sirex noctilio females are known to be attracted to stem sections of stressed pine trees for oviposition. The volatile profiles and attractiveness of Eastern white pine (Pinus strobus) and two chemotypes of Scots pine (P. sylvestris) were compared after stem injection with herbicide. In general, trap captures on herbicide-treated trees were higher than on controls. The high-carene chemotype of Scots pine captured the highest numbers of females, followed by the low-carene chemotype, and finally the Eastern white pine. Herbicide-treated trees of both species emitted larger quantities of volatiles than the controls. The herbicide treatment induced higher volatile emission rates in the Scots pine chemotypes than in white pine, although there was no difference between the two chemotypes. However, qualitative differences were found between the volatile profiles of the two species as well as between the two Scots pine chemotypes, which could account for the differential attractiveness of the species and chemotypes tested.

Male-produced pheromone in the European woodwasp, Sirex noctilio.

A male-produced pheromone that attracts both males and females was identified for the European woodwasp, Sirex noctilio, a serious pest of pine trees. Males displayed excitatory behaviors when placed in groups, and were attracted to the odors from males that were 2-5-d-old, but not to odors from males that were 0-1-d-old. An unsaturated short-chain alcohol, (Z)-3-decen-1-ol, was discovered in samples collected on SuperQ filters over groups of males and identified by using micro-derivatization reactions and gas chromatography coupled with mass spectrometry (GC-MS). The compound was not detected in volatile samples from females. Gas chromatography coupled electroantennographic detection (GC-EAD) of antennae from males exposed to male headspace odors produced strong antennal responses to the main peak of (Z)-3-decen-1-ol, as well as to an unknown minor component that had a similar retention time. Antennae from both males and females responded to synthetic (Z)-3-decen-1-ol. Several different synthetic candidates for the GC-EAD active minor components were selected based on GC-MS and GC-EAD responses to male headspace collections. These synthetic compounds were tested for antennal activity using GC-EAD, and those that produced strong responses were blended with the major component and tested for male attraction in the Y-tube olfactometer at different concentrations and ratios. Males tested in the Y-tube olfactometer were attracted to a synthetic blend of (Z)-3-decen-1-ol and (Z)-4-decen-1-ol at a ratio of 100:1. Whereas the addition of some suspected minor compounds reduced attraction, the addition of a third compound found in male emanations that produced strong male antennal responses, (E,E)-2,4-decadienal (at a ratio of 100:1:1), resulted in attraction of both males (Y-tube and wind tunnel) and females (wind tunnel).

Arboreal insects associated with herbicide-stressed Pinus resinosa and Pinus sylvestris used as Sirex noctilio trap trees in New York.

In September of 2004, Sirex noctilio F. (Hymenoptera: Siricidae) was detected in New York State and later found to be established over a larger area, including parts of southeastern Canada and the northeastern United States. A key component of S. noctilio detection and management plans in other parts of the world where S. noctilio has become established are chemically girdled trap trees. Trap tree usage in North America is confounded by the presence of diverse communities of organisms that inhabit dead and dying trees. We trapped a portion of the arboreal insect community arriving at Pinus resinosa Ait. and Pinus sylvestris L., trap trees girdled 3 mo before (April), one month before (June), and at S. noctilio flight (July) in central New York. Multiple-funnel traps attached to trap trees captured 30,031 individuals from 109 species of Scolytinae, Cerambycidae, and Siricidae. Ips pini (Say) and Ips grandicollis (Eichhoff) accounted for almost 50% of the scolytines captured at trap trees and were present on all girdling dates. Significantly more scolytines and cerambycids were captured on P. sylvestris compared with P. resinosa, but species richness of captured insects did not differ between the two trees. More total and conifer-inhabiting scolytines and cerambycids were captured in traps on trees girdled in April and June and higher observed species richness was found on trees girdled in April and controls. Results from this study suggest a large community of arboreal insects and associated organisms are attracted to chemically girdled trap trees and likely interact with S. noctilio.

Common mortality factors of woodwasp larvae in three northeastern United States host species.

Very little is presently known about the natural enemies and mortality factors associated with siricids (Hymenoptera: Siricidae) in the United States of America (USA), especially those that may directly affect the woodwasp, Sirex noctilio Fabricius (Hymenoptera: Siricidae). S. noctilio is an invasive woodwasp, is considered a major economic pest of pine, and has a severe effect on North American pine species planted in the Southern hemisphere. The mortality factors of siricid larvae were determined in three host species (Pinus sylvestris, Pinus resinosa, and Pinus strobus) from naturally infested trees in the northeastern USA. Siricid larvae were classified at the time of sampling as: (1) healthy, (2) parasitized by rhyssines (Hymenoptera: Ichneumonidae), (3) parasitized by Ibalia spp. (Hymenoptera: Ibaliidae), (4) parasitized by nematodes (Tylenchida: Neotylenchidae), and (5) dead from unknown causes. Combining data from the three host species, the average percentage of larvae that were healthy was 66%, 10% of the larvae were parasitized by rhyssines, 18% were parasitized by Ibalia spp., 1% were infected with unidentified nematodes, and about 5% of the larvae were dead in the galleries. Information from this study has important implications for understanding population regulation mechanisms in an invasive species, and will be critical for developing integrated pest management plans for S. noctilio.

Monoalkenes as contact sex pheromone components of the woodwasp Sirex noctilio.

A pheromone on the cuticle of females of the woodwasp Sirex noctilio, a recently introduced pest of pines in North America, induces conspecific males to attempt copulation. Dead females washed with hexane did not elicit copulation attempts from males, whereas reapplication of a female hexane body wash onto the cuticle of dead females elicited copulation attempts by 65% of males tested. Analysis of the hexane extract revealed saturated and unsaturated hydrocarbons as major components of the female cuticle. Behavior-guided fractionation of the female body wash led to the identification of three components, (Z)-7-heptacosene, (Z)-7-nonacosene, and (Z)-9-nonacosene, of the sex pheromone of S. noctilio that elicited copulatory responses from males.

Laboratory and field response of the emerald ash borer (Coleoptera: Buprestidae), to selected regions of the electromagnetic spectrum.

Retinal sensitivity of Agrilus planipennis Fairmaire (Coleoptera: Buprestidae) was examined with an aim to improve trap efficacy for the beetle. Electroretinogram (ERG) recordings from dark-adapted compound eyes of male and female were measured at different wavelengths across the spectrum ranging from 300 to 700 nm. The spectral sensitivity curves revealed peaks in the UV (340 nm), the violet/purple (420-430 nm), blue (460 nm), and green (540-560 nm) regions of the spectrum. Females were sensitive to red regions of the spectrum (640-670 nm), whereas males were not. A spectrophotometer was used to measure the wavelength and reflectance for ash foliage, purple corrugated plastic traps, as well as the elytra and abdomen of adult A. planipennis. Traps were painted using colors based on ERG and spectrophotometer measurements and compared with purple corrugated plastic traps currently used by the USDA-APHIS-PPQ-EAB National Survey. In a field assay conducted along the edges of several A. planipennis-infested ash stands, there were no significant differences in trap catch among green, red, or purple treatments. Dark blue traps caught significantly fewer A. planipennis than red, light green, or dark purple traps. In a second assay where purple and green treatments were placed in the mid canopy of ash trees (approximately 13 m in height), trap catch was significantly higher on green treatments. We hypothesize that when placed in the mid-canopy, green traps constitute a foliage-type stimulus that elicits food-seeking and/or host seeking behavior by A. planipennis.