D. Barry Lyons

The overwintering physiology of the emerald ash borer, Agrilus planipennis Fairmaire (Coleoptera: Buprestidae).

Ability to survive cold is an important factor in determining northern range limits of insects. The emerald ash borer (Agrilus planipennis) is an invasive beetle introduced from Asia that is causing extensive damage to ash trees in North America, but little is known about its cold tolerance. Herein, the cold tolerance strategy and mechanisms involved in the cold tolerance of the emerald ash borer were investigated, and seasonal changes in these mechanisms monitored. The majority of emerald ash borers survive winter as freeze-intolerant prepupae. In winter, A. planipennis prepupae have low supercooling points (approximately -30°C), which they achieve by accumulating high concentrations of glycerol (approximately 4M) in their body fluids and by the synthesis of antifreeze agents. Cuticular waxes reduce inoculation from external ice. This is the first comprehensive study of seasonal changes in cold tolerance in a buprestid beetle.

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.

Could phenotypic plasticity limit an invasive species? Incomplete reversibility of mid-winter deacclimation in emerald ash borer

The emerald ash borer (Agrilus planipennis, Coleoptera: Buprestidae) is a wood-boring invasive pest devastating North American ash (Fraxinus spp.). A. planipennis overwinters primarily as a freeze-avoiding prepupa within the outer xylem or inner bark of the host tree. The range of this species is expanding outward from its presumed introduction point in southwestern Michigan. We hypothesized that loss of cold tolerance in response to mid-winter warm spells could limit survival and northern distribution of A. planipennis. We determined whether winter-acclimatised A. planipennis prepupae reduced their cold tolerance in response to mid-winter warm periods, and whether this plasticity was reversible with subsequent cold exposure. Prepupae subjected to mid-winter warm spells of 10 and 15°C had increased supercooling points (SCPs) and thus reduced cold tolerance. This increase in SCP was accompanied by a rapid loss of haemolymph cryoprotectants and the loss of cold tolerance was not reversed when the prepupae were returned to −10°C. Exposure to temperatures fluctuating from 0 to 4°C did not reduce cold hardiness. Only extreme warming events for several days followed by extreme cold snaps may have lethal effects on overwintering A. planipennis populations. Thus, distribution in North America is likely to be limited by the presence of host trees rather than climatic factors, but we conclude that range extensions of invasive species could be halted if local climatic extremes induce unidirectional plastic responses.

Comparison of Male and Female Emerald Ash Borer (Coleoptera: Buprestidae) Responses to Phoebe Oil and (Z)-3-Hexenol Lures in Light Green Prism Traps

ABSTRACT We conducted trapping experiments for the emerald ash borer, Agrilus planipennis Fairmaire (Coleoptera: Buprestidae) in Michigan, USA, and Ontario, Canada, to compare unbaited light green sticky prism traps with traps baited with phoebe oil, (Z)-3-hexenol (Z3-6:OH), or blends of other green leaf volatiles (GLVs) with Z3-6:OH. Traps were placed in the lower canopy of ash trees (Fraxinus spp.). Catches with Z3-6:OH—baited traps showed a significant male bias and these traps caught significantly more males than the unbaited controls at both sites. They were also superior to phoebe oil-baited traps and those baited with GLV blends. Catches with phoebe oil showed a significant female bias but there was no difference in the number of females captured between traps baited with phoebe oil or Z3-6:OH lures. Catches were analyzed at regular time intervals to examine the response of A. planipennis to the lures over the course of the flight season. Z3-6:OH—baited traps consistently caught more males than the controls at each interval throughout the flight season. Catches of females with Z3-6:OH and phoebe oil were significantly better than the controls early in the flight season but declined to control levels by midseason. Our results suggest that Z3-6:OH—baited green traps placed in the ash canopy would be a superior lure for detecting and monitoring A. planipennis throughout the flight season.

Towards the Development of an Autocontamination Trap System to Manage Populations of Emerald Ash Borer (Coleoptera: Buprestidae) With the Native Entomopathogenic Fungus, Beauveria bassiana

ABSTRACT Emerald ash borer, Agrilus planipennis Fairmaire (Coleoptera: Buprestidae) is an invasive species from Asia that was discovered in North America Canada, in 2002. Herein, we describe studies to develop an autocontamination trapping system to disseminate Beauveria bassiana to control beetle populations. The standard trap for emerald ash borer in Canada is a light green prism trap covered in an insect adhesive and baited with (Z)-3-hexenol. We compared of green multifunnel traps, green intercept panel traps (both with and without fluon coating) and green prism traps for capturing emerald ash borer in a green ash plantation. The coated green multifunnel traps captured significantly more males and more females than any other trap design. We examined the efficacy of two native B. bassiana isolates, INRS-CFL and L49–1AA. In a field experiment the INRS-CFL isolate attached to multifunnel traps in autocontamination chambers retained its pathogenicity to emerald ash borer adults for up to 43 d of outdoor exposure. Conidia germination of the INRS-CFL isolate was >69% after outdoor exposure in the traps for up to 57 d. The L49–1AA isolate was not pathogenic in simulated trap exposures and the germination rate was extremely low (<5.3%).Mean (±SEM) conidia loads on ash borer adults after being autocontaminated in the laboratory using pouches that had been exposed in traps out of doors for 29 d were 579,200 (±86,181) and 2,400 (±681) for the INRS-CFL and the L49–1AA isolates, respectively. We also examined the fungal dissemination process under field conditions using the L49–1AA isolate in a green ash plantation. Beetles were lured to baited green multifunnel traps with attached autocontamination chambers. Beetles acquired fungal conidia from cultures growing on pouches in the chambers and were recaptured on Pestick-coated traps. In total, 2,532 beetles were captured of which 165 (6.5%) had fungal growth that resembled B. bassiana. Of these 25 beetles were positive for the L49–1AA isolate.

Host selection by Agrilus planipennis (Coleoptera: Buprestidae): inferences from sticky-band trapping

Abstract Sticky-band trapping experiments were undertaken in 2003–2006 to examine the host-seeking behaviour of the emerald ash borer, Agrilus planipennis Fairmaire, in woodlots in southwestern Ontario, Canada. The female proportion of A. plannipennis emerging from host logs ranged from 0.414 to 0.582. Landings on sticky-band traps varied more with the female proportion, ranging from 0.392 to 0.889, with the majority in the upper range, suggesting behavioural differences between the sexes. Correlations between landing density and tree size measured as diameter at breast height were positive or showed no relationship. In some locations more beetles were captured on the south side of the tree than on the north side; however, there was no difference between these cardinal directions at other locations. Numbers of captured beetles were never significantly greater on the north side of boles. We observed greater landing densities of adults of both sexes on traps on trees along the edges of woodlots than on trees within the woodlots. When given a choice under natural conditions, beetles landed almost exclusively on host trees (Fraxinus pennsylvanica Marsh. (Oleaceae)) rather than on other common trees species (Carya ovata (Mill.) K. Koch (Juglandaceae), Tilia americana L. (Tiliaceae), and species of Acer L. (Aceraceae)) found in the same woodlots. Our data suggest that A. planipennis make host-selection decisions while in flight rather than landing randomly. Implications for monitoring A. plannipennis using sticky-band traps and understanding its host-seeking behaviour are discussed.

Microsatellite population genetics of the emerald ash borer (Agrilus planipennis Fairmaire): comparisons between Asian and North American populations

The emerald ash borer (EAB) (Agrilus planipennis Fairmaire) (Coleoptera; Buprestidae), is an invasive wood-boring beetle native to northeast Asia. This species was first detected in Michigan USA in 2002, and is a significant threat to native and ornamental ash tree species (Fraxinus spp.) throughout North America. We characterized seven polymorphic microsatellite markers for EAB and used these to investigate EAB population structure in the early invasive populations within North America and in comparison with Asia. We found 2–9 alleles per microsatellite locus, no evidence of linkage disequilibrium, and no association with known coding sequences, suggesting that these markers are suitable for population genetic analysis. Microsatellite population genetic structure was examined in 48 EAB populations sampled between 2003 and 2008 from five regions, three in the introduced range, Michigan (US) and Ontario and Quebec (Canada) and two Asian regions, China and South Korea, where EAB is native. We found significant genetic variation geographically but not temporally in EAB populations. Bayesian clustering analyses of individual microsatellite genotypes showed strong clustering among multiple North American populations and populations in both China and South Korea. Finally, allelic richness and expected heterozygosity were higher in the native range of EAB, but there was no difference in observed heterozygosity, suggesting a significant loss of alleles upon introduction but no significant change in the distribution of alleles within and among individuals.

The use of fluorescent powders to track autocontamination of emerald ash borer (Coleoptera: Buprestidae) by the entomopathogen Beauveria bassiana (Ascomycota: Hypocreales)

ABSTRACT We evaluated the use of fluorescent powders for tracking dispersal by the emerald ash borer, Agrilus planipennis Fairmaire (Coleoptera: Buprestidae), of Beauveria bassiana isolates from an autocontamination device. Neither of the two DayGlow powders tested (Arc Yellow and Aurora Pink) interfered with fungal germination or growth, nor did they affect survival of beetles in the laboratory, or affect virulence of the fungus. The powders persisted at least 10 days out-of-doors on dead beetles in sticky band traps, and at least 14 days on pouches inside autocontamination traps. During field trials of autocontamination traps with powder-dusted fungal pouches in southwestern Ontario, 8.0% of the 4010 beetles captured in green prism and sticky-band traps were positive for fluorescent powders. Only half (46.2–57.8%) of the powder-positive beetles actually carried viable fungal conidia, as determined by plating of beetle rinses, possibly as a result of patchy growth of fungal isolates and reduced conidia production on pouch surfaces during the 16-day trapping experiment. The presence of viable conidia (either one or both isolates) on about 10% of beetles that did not carry any visible powder particles may be an indication of horizontal transmission of the fungus by beetles that had visited the autocontamination traps.