Damon J. Crook

Development of a Host-Based Semiochemical Lure for Trapping Emerald Ash Borer Agrilus planipennis (Coleoptera: Buprestidae)

Abstract Bark volatiles from green ash Fraxinus pennsylvanica were tested for electrophysiological activity by Agrilus planipennis using gas chromatographic-electroantennographic detection (GC-EAD) and for behavioral activity using baited purple traps in Michigan. GC-EAD analysis of the headspace volatiles of bark tissue samples from 0- and 24-h-old fully girdled (stressed) ash trees showed that the latter had elevated sesquiterpene levels. Six of the elevated compounds consistently elicited antennal responses by both male and female A. planipennis. Five of the antennally active compounds were identified as α-cubebene, α-copaene, 7-epi-sesquithujene, trans-β-caryophyllene, and α-humulene (α-caryophyllene). The sixth EAD-active compound remains unidentified. We monitored capture of adult A. planipennis on traps baited with several combinations of ash tree volatiles. Treatments included two natural oil distillates (Manuka and Phoebe oil) that were found to contain, respectively, high concentrations of four and five of the six antennally active ash bark volatiles. A four-component leaf lure developed by the USDA Forest Service and Canadian Forest Service was also tested. In three separate field studies, Manuka oil–baited traps caught significantly more adult beetles than unbaited traps. Lures designed to release 5, 50, and 500 mg of Manuka oil per day all caught more insects than unbaited traps. In a field test comparing and combining Phoebe oil with Manuka oil, Phoebe oil–baited traps caught significantly more beetles than either Manuka oil–baited traps or unbaited traps. We hypothesize that the improved attractancy of Phoebe oil to A. planipennis over Manuka oil is caused by the presence of the antennally active sesquiterpene, 7-epi-sesquithujene.

Chemical Ecology of the Emerald Ash Borer Agrilus planipennis

The emerald ash borer (EAB), Agrilus planipennis Fairmaire (Coleoptera: Buprestidae) is a serious invasive pest that has caused devastating mortality of ash trees (Fraxinus sp., Oleaceae) since it was first identified in North America in 2002. Shortly after its discovery, surveys were conducted, based on the visual inspection of trees. The shortcomings of visual surveys have led to a critical research need to find an efficient survey method for detecting A. planipennis infestations. Here, we present a review of research that has led to the development of effective trapping methods for A. planipennis. Studies on the insect’s biology and behavior have led to the identification of several potential attractants as well as the design of a visually attractive trap. The ongoing challenge in developing an optimally efficient trapping methodology for A. planipennis will involve finding the best combination of variables, such as trap shape, trap color (or other visual properties), trap placement, lure components, as well as the ratios and release rates of those components.

Laboratory and Field Response of the Emerald Ash Borer (Coleoptera: Buprestidae), to Selected Regions of the Electromagnetic Spectrum

ABSTRACT 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 (≈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.

Optimization of Trap Color for Emerald Ash Borer (Coleoptera: Buprestidae)

ABSTRACT Field assays were performed to determine the optimal color for Agrilus planipennis Fairmaire (Coleoptera; Buprestidae) traps. Previous studies have found that more A. planipennis are caught on purple or green traps than traps of other colors. In three studies, we evaluated various shades of purple, wavelengths of green (500–570 nm), and greens of different reflectance (from 9 to 66%). In all tests, traps of corrugated plastic in standard, commercially available purple (currently used to survey A. planipennis) and a customized green color were used as bases for comparison. Among purple traps, a paint color previously shown to be generally attractive to buprestids caught significantly more A. planipennis adults than traps coated with paints containing more blue or red, or traps constructed of the standard purple plastic. Among traps with maximum reflectance at varying green wavelengths, those ranging in wavelength from 525 to 540 nm caught significantly more adult A. planipennis than traps of other wavelengths. In the 530–540 nm range of the electromagnetic spectrum, there was no significant difference among traps in the 23–66% reflectance range, but traps painted with a peak reflectance of 49% caught more beetles than purple or the custom green plastic traps. Male to female ratio was highest on green traps.

Evidence for a Volatile Pheromone in Agrilus planipennis Fairmaire (Coleoptera: Buprestidae) that Increases Attraction to a Host Foliar Volatile

ABSTRACT Analysis by gas chromatography/mass spectrometry (GC/MS) of volatiles from virgin female emerald ash borer, Agrilus planipennis Fairmaire confirmed the emission of (3Z)-lactone [(3Z)-dodecen-12-olide] but not its geometric isomer, (3E)-lactone [(3E)-dodecen-12-olide]. Gas chromatographic/electroantennographic (GC/EAD) analysis of synthetic (3Z)-lactone, which contained 10% (3E) -lactone, showed a strong response of male and female antennae to both isomers. EAG analysis with 0.01 - to100-µg dosages showed a positive dose response, with females giving significantly higher responses than males. In field experiments with sticky purple prism traps, neither lactone isomer affected catches when combined with ash foliar or cortical volatiles (green leaf volatiles or Phoebe oil, respectively). However, on green prism traps, the (3Z)-lactone significantly increased capture of male A. planipennis when traps were deployed in the canopy. Captures of males on traps with both (3E)-lactone and (3Z)-hexenol or with (3Z)-lactone and (3Z)-hexenol were increased by 45–100%, respectively, compared with traps baited with just (3Z)-hexenol. In olfactometer bioassays, males were significantly attracted to (3E) -lactone, but not the (3Z) -lactone or a 60:40 (3E): (3Z) blend. The combination of either (3E)- or (3Z)-lactone with Phoebe oil was not significantly attractive to males. Males were highly attracted to (3Z)-hexenol and the (3Z)-lactone + (3Z)-hexenol combination, providing support for the field trapping results. These data are the first to demonstrate increased attraction with a combination of a pheromone and a green leaf volatile in a Buprestid species.

Influence of Trap Color and Host Volatiles on Capture of the Emerald Ash Borer (Coleoptera: Buprestidae)

ABSTRACT Field trapping assays were conducted in 2009 and 2010 throughout western Michigan, to evaluate lures for adult emerald ash borer, A. planipennis Fairmaire (Coleoptera: Buprestidae). Several ash tree volatiles were tested on purple prism traps in 2009, and a dark green prism trap in 2010. In 2009, six bark oil distillate lure treatments were tested against manuka oil lures (used in 2008 by USDA APHIS PPQ emerald ash borer cooperative program). Purple traps baited with 80/20 (manuka/phoebe oil) significantly increased beetle catch compared with traps baited with manuka oil alone. In 2010 we monitored emerald ash borer attraction to dark green traps baited with six lure combinations of 80/20 (manuka/phoebe), manuka oil, and (3Z)-hexenol. Traps baited with manuka oil and (3Z)-hexenol caught significantly more male and total count insects than traps baited with manuka oil alone. Traps baited with manuka oil and (3Z)-hexenol did not catch more beetles when compared with traps baited with (3Z)-hexenol alone. When compared with unbaited green traps our results show that (3Z)-hexenol improved male catch significantly in only one of three field experiments using dark green traps. Dark green traps caught a high number of A. planipennis when unbaited while (3Z)-hexenol was seen to have a minimal (nonsignificant) trap catch effect at several different release rates. We hypothesize that the previously reported kairomonal attractancy of (3Z)-hexenol (for males) on light green traps is not as obvious here because of improved male attractancy to the darker green trap.

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.

Relation of Color, Size, and Canopy Placement of Prism Traps in Determining Capture of Emerald Ash Borer (Coleoptera: Buprestidae)

Abstract In 2008 we compared numbers of emerald ash borer, Agrilus planipennis Fairmaire, captured on glue-coated prism traps of different sizes (standard, double-length narrow, and quarter), colors (green and purple), and height in relation to the canopy of ash host trees (mid-canopy (10–13 m) and ground level (1.5 m)). Standard-size prism traps caught more A. planipennis than did quarter-size prism traps, but catch per square metre of surface area did not differ significantly among the three trap sizes. Twenty percent of quarter-size prism traps failed to catch a single beetle, while all traps of the two larger sizes were successful. The larger traps therefore appear to be more useful as detection tools. In 2009 we compared purple and green standard-size prism traps at three heights: midcanopy (13 m), lower canopy (6 m), and ground (1.5 m). Green traps caught more adult emerald ash borers than did purple traps in the mid and lower canopy, but there was no difference between traps hung at 1.5 m. The ratio of male to female adult emerald ash borers was also higher on green than on purple traps at all three heights.

Improving detection tools for the emerald ash borer (Coleoptera: Buprestidae): comparison of prism and multifunnel traps at varying population densities.

ABSTRACT The current emerald ash borer survey trap used in the United States is a prism trap constructed from a stock purple corrugated plastic. In recent years, several colors (particularly shades of green and purple) have been shown to be more attractive to the emerald ash borer than this stock color. Our goal was to determine if plastics produced with these colors and incorporated into prism traps can improve and serve as a new alternative to plastics already in use for the emerald ash borer survey. The plastics were tested in moderate to heavily infested areas in Michigan in two initial studies to test their effectiveness at catching the emerald ash borer. Because results from studies performed in heavily infested sites may not always correspond with what is found along the edges of the infestation, we compared trap catch and detection rates (recording at least one catch on a trap over the course of the entire trapping season) of several trap types and colors at sites outside the core of the currently known emerald ash borer infestation in a nine-state detection tool comparison study. Two of the new plastics, a (Sabic) purple and a medium-dark (Sabic) green were incorporated into prism traps and tested alongside a standard purple prism trap and a green multifunnel trap. In areas with lower emerald ash borer density, the new purple (Sabic) corrugated plastic caught more beetles than the current purple prism trap, as well as more than the medium-dark green (Sabic) prism and green multifunnel traps. Sabic purple traps in the detection tools comparison study recorded a detection rate of 86% compared with 73, 66, and 58% for the standard purple, Sabic green, and green multifunnel traps, respectively. These detection rates were reduced to 80, 63, 55, and 46%, respectively, at low emerald ash borer density sites.

Distribution and Fine Structure of Antennal Sensilla in Emerald Ash Borer (Coleoptera: Buprestidae)

Abstract The antennal sensilla of the emerald ash borer, Agrilus planipennis Fairmaire (Coleoptera: Buprestidae), were examined using scanning and transmission electron microscopy. Male and female antennae have a scape, pedicel, and nine flagellomeres. Both male and female antennae share five sensillum types: sensilla chaetica (mechanoreceptors), three types of sensilla basiconica (olfactory), and uniporous gustatory/taste sensilla. Apical depressions containing large sensory fields of uniporous sensilla were seen on the eight most distal flagellomeres of both sexes. Counts of sensillum types showed that males possessed significantly more uniporous sensilla than females. We hypothesize that antennal contact is important for mate recognition by male A. planipennis. The distal apices of the eight outer flagellomeres were seen to have “tufts” composed of two types of sensilla basiconica. A third type of sensilla basiconica was observed within the perimeter of the uniporous sensory fields. The structure and putative function of each sensillum type are discussed.