Patterns in the within‐tree distribution of the emerald ash borer Agrilus planipennis (Fairmaire) in young, green‐ash plantations of south‐western Ontario, Canada

Abstract

Abstract1 The emerald ash borer Agrilus planipennis Fairmaire (Coleoptera: Buprestidae) is a serious exotic pest of ash trees (Fraxinus spp.) in North America, and is responsible for the deaths of millions of trees in Ontario and Michigan. One of the greatest challenges facing the successful management of the pest is the ability to accurately detect its presence in a tree.2 Observations were made on A. planipennis larval feeding galleries found within 65 young, green‐ash trees cut from plantations in Essex County, Ontario, Canada. The within‐tree distributions of feeding galleries were described in relation to height‐above‐ground, stem diameter, bark thickness and stem aspect.3 Galleries were not distributed randomly or evenly; minimum boundaries of stem diameter and bark thickness and a maximum boundary of height‐above‐ground were detected. Indications of maximum boundaries for stem diameter and bark thickness were also observed. Galleries were found most often on the south‐west side of the tree.4 Using the technique of upper boundary regression, we were able to identify significant quadratic relationships between A. planipennis gallery density and stem diameter and bark thickness, as well as a significant negative linear relationship between gallery density and height‐above‐ground.5 Agrilus planipennis gallery density in newly‐infested trees was lower than in previously‐infested trees, and was observed to peak at smaller stem diameters and bark thicknesses than in previously‐infested trees.6 Survey teams would increase their probability of detecting new A. planipennis infestations by initiating searches for exit holes and feeding galleries in trunk sections and branches of approximately 7 cm in diameter.

Outbreak of Phoracantha semipunctata in Response to Severe Drought in a Mediterranean Eucalyptus Forest

“…The density of P. semipunctata (exit holes per m 2 stem surface area) was derived for each tree using DBHOB and assuming a perfect cylinder of 2 m in height. These methods closely followed other studies, where Cerambycid beetle populations were estimated using only the bottom 2 m of trees [35], and is justified by within-tree studies that have shown this area represents the majority of beetle emergence [36] Seaton (unpublished data). To calculate adult emergence (ha −1 ) tree densities found from surveys, and population levels per tree for each forest area (averaged over all sites measured) were then scaled-up and used to calculate total estimated borer populations for each minimally and severely drought-affected forest areas.…”

Neighboring Tree Effects and Soil Nutrient Associations with Surviving Green Ash (Fraxinus pennsylvanica) in an Emerald Ash Borer (Agrilus planipennis) Infested Floodplain Forest

“…It is possible that the number of EAB exit holes on the lower trunk do not reflect the number in the canopy, which were not counted. For example, one study has shown locations where larvae development increased on stems/branches up to 13 cm in diameter and occurred at certain bark thickness (1.5-5 mm) [32]. Another study revealed that two mid-canopy branches (sampling two 25 cm sections each) were 18 times more likely to allow detection of low density EAB larvae than a trunk window (25 cm wide by 25% circumference of trunk bark removal above 1.3 m) [33].…”

Scientific Opinion on a technical file submitted by the US Authorities to support a request to list a new option among the EU import requirements for wood of Agrilus planipennis host plants

“…In China, the North American ash species planted as ornamentals (Fraxinus americana, F. pennsylvanica and F. velutina) are more susceptible to EAB attack than the Asian ash species and outbreaks have almost exclusively occurred on those introduced tree species (Liu et al, 2003;Zhao et al, 2007). In North America -the USA and Canada -EAB was first identified in 2002 (Cappaert et al, 2005;Timms et al, 2006). The larval development of the pest occurs exclusively in Fraxinus spp., although females occasionally lay eggs on other tree genera (Anulewicz et al, 2008).…”

“…It usually builds a pupal cell (overwintering chamber) in the xylem. When a two year life cycle is observed, second and third instar larvae may also overwinter in their galleries between the xylem and the phloem (Timms et al, 2006;Wei et al, 2007). Overwintering prepupae have low supercooling points reaching -30 °C, which are achieved by accumulation of high concentrations of glycerol and synthesis of antifreeze agents, contained in the haemolymph.…”

“…A study on the patterns in the within-tree distribution of EAB performed by Timms et al (2006) shows that larval galleries are most likely to be found in trees with bark thickness of 1.5 -5 mm and stem diameter of 4 -13 cm, predominantly on the southwestern side of the trunk. The authors suggest that bark thickness is the most important variable affecting the distribution of the galleries.…”