Density of Emerald Ash Borer (Coleoptera: Buprestidae) Adults and Larvae at Three Stages of the Invasion Wave

Commodity risk assessment of ash logs from the US treated with sulfuryl fluoride to prevent the entry of the emerald ash borer Agrilus planipennis

The European Commission submitted to the EFSA Panel on Plant Health a dossier by USDA proposing to use sulfuryl fluoride on ash log shipments to treat Agrilus planipennis for phytosanitary certification. After collecting additional evidence from USDA APHIS, external experts and literature, the Panel performed a quantitative assessment on the likelihood of pest freedom from A. planipennis, at the point of entry in the EU, of two different commodities fumigated with sulfuryl fluoride: (a) ash logs with bark; and (b) debarked ash logs. An expert judgement is given on the likelihood of pest freedom taking into consideration the measures acting on the pest, including uncertainties associated with the assessment. The likelihood of pest freedom from A. planipennis is lower for ash logs with bark compared with debarked ash logs. With 95% certainty, the Panel concludes that between 9,740 and 10,000 containers of ash logs with bark per 10,000 and between 9,989 and 10,000 containers of debarked ash logs per 10,000 will be free from A. planipennis, when fumigated with sulfuryl fluoride at the specific treatment regime proposed by the USDA APHIS.

Lignans dramatically enhance the resistance of Fraxinus velutina Torr. by adjusting the dominant bacterium group of Agrilus planipennis Fairmaire

BACKGROUND

Velvet ash (Fraxinus velutina Torr.) is an important wood and ornamental tree species. Emerald ash borer (EAB), Agrilus planipennis Fairmaire, is a major wood borer of velvet ash. The aim of this study was to identify the secondary metabolites of velvet ash involved in regulating the dominant bacterium group of EAB.

RESULTS

The amount of lignans in the phloem of infested trees had increased by 290.96% because of A. planipennis infection. The addition of lignans to the artificial diet significantly reduced the weight of the larvae and decreased the dominant bacterial group in the larval midgut, such as Pseudomonadaceae, Xanthomonadaceae, and Enterobacteriaceae. The FvPLR1, a key gene for lignan synthesis, was obtained based on the phloem transcriptome of velvet ash. The expression of FvPLR1 in the phloem of the infested tree was significantly higher than that in the noninfested tree. Meanwhile, FvPLR1 silenced by virus-induced gene silencing showed that its expression level and the lignan content were decreased by 69.91% and 31.65%, respectively. Interestingly, silencing FvPLR1 induced alterations in the dominant bacteria group in the larvae, with the reverse trend in the lignan-fed treatment.

CONCLUSION

The evidence showed that FvPLR1 was a positive regulator. The increasing synthesis of lignans leads to resistance improvement in velvet ash, which will provide comprehensive insights into the tree defense system to wood borer infestation. © 2021 Society of Chemical Industry.

Evaluation of Trapping Schemes to Detect Emerald Ash Borer (Coleoptera: Buprestidae)

Management responses to invasive forest insects are facilitated by the use of detection traps ideally baited with species-specific semiochemicals. Emerald ash borer, Agrilus planipennis Fairmaire, is currently invading North American forests, and since its detection in 2002, development of monitoring tools has been a primary research objective. We compared six trapping schemes for A. planipennis over 2 yr at sites in four U.S. states and one Canadian province that represented a range of background A. planipennis densities, canopy coverage, and ash basal area. We also developed a region-wide phenology model. Across all sites and both years, the 10th, 50th, and 90th percentile of adult flight occurred at 428, 587, and 837 accumulated degree-days, respectively, using a base temperature threshold of 10°C and a start date of 1 January. Most trapping schemes captured comparable numbers of beetles with the exception of purple prism traps (USDA APHIS PPQ), which captured significantly fewer adults. Trapping schemes varied in their trap catch across the gradient of ash basal area, although when considering trap catch as a binary response variable, trapping schemes were more likely to detect A. planipennis in areas with a higher ash component. Results could assist managers in optimizing trap selection, placement, and timing of deployment given local weather conditions, forest composition, and A. planipennis density.

Species Diversity and Assemblages of Cerambycidae in the Aftermath of the Emerald Ash Borer (Coleoptera: Buptrestidae) Invasion in Riparian Forests of Southern Michigan

Extensive ash (Fraxinus spp.) mortality has been reported across much of the area in eastern North America invaded by emerald ash borer (Agrilus planipennis Fairmaire), but indirect effects of emerald ash borer invasion on native forest insects are not well-studied. We assessed cerambycid beetle (Coleoptera: Cerambycidae) species captured in baited cross-vane panel traps during the 2017 and 2018 growing seasons. Traps were placed in 12 riparian forest sites distributed across three watersheds selected to represent the temporal gradient of the emerald ash borer invasion from southeastern to southwestern Michigan. Although ash species originally dominated overstory vegetation in all sites, >85% of ash basal area has been killed by emerald ash borer. We captured a total of 3,645 beetles representing 65 species and five subfamilies. Species assemblages in southeast sites, with the longest history of emerald ash borer invasion, differed from those in south central and southwest Michigan, which were similar. These differences were largely due to three species, which accounted for >60% of beetle captures in southeast Michigan. Associations among site-related variables and beetle captures indicated cerambycid species assemblages were associated most strongly with abundance and decay stage of coarse woody debris. During both years, >90% of cerambycid species were captured by mid-summer but seasonal activity differed among and within tribes. Numbers of beetles captured by canopy and ground traps were similar but species richness was higher in canopy traps than ground traps. Results suggest inputs of emerald ash borer-killed ash can have temporally lagged, secondary effects on cerambycid communities.