1. Methods: Branch Survey Methods: Trapping Survey
The Spatial Distribution and Density of the Emerald Ash Borer Infestation in Rock Island and Moline, IL
Kendall Smith, Victoria Lason, Morgan Conley, Dr. Tierney Brosius, Dr. Michael Reisner
Department of Environmental Studies, Augustana College
Introduction
Figure 2. Study area trap locations of 2014 in Rock Island and Moline, IL are indicated by the green and purple circles (green and purple multifunnel traps) and black triangles (prism traps).
Results
The Emerald Ash Borer (EAB) Agrilus planipennis Fairmaire is a destructive colonizer of ash trees that was identified in Detroit, Michigan in 2002 (Figure 1)(Siegert et al. 2014). Mature EAB lay eggs in bark crevices on ash trees after exiting their hosts between May and July. EAB larvae bore into their new host and begin feeding on phloem and cambium, girdling the trunk and branches. EAB colonizes both stressed and healthy ash trees, though adults prefer to feed on foliage from open-grown trees.
Visual assessments have been a common method for identifying EAB infestations, with surveyors looking for symptoms such as canopy thinning/dieback, bark splitting, epicormic shooting, and D-shaped exit holes. However, a 1-2 year time lag between the initial infestation and the appearance of visible symptoms allows the invasion front to progress past an area before resource managers are aware of its presence (Persad et al. 2015). To adequately manage the EAB invasion, researchers have focused on developing trapping techniques that are capable of detecting low-density EAB populations. Similarly, branch sampling has been used to determine the distribution and densities of EAB larval populations. These branch samples involve removing a branch from a suspected EAB host and peeling back the bark to reveal serpentine galleries. The amount of larvae found within these branches can be quantified to estimate the density of the EAB infestation.
EAB was first discovered in Hasselroth Park in Rock Island, IL in In the summer of 2014 branch surveys and traps were utilized throughout Rock Island and Moline, IL to note the spread of EAB, while in summer of 2015 branch surveys were used only on Rock Island, IL Ash Trees (Figure 5 & 6). The research objectives of this study were to determine the spatial distribution of the Emerald Ash Borer (EAB) beetle infestation in Rock Island, IL and Moline, IL, the density of EAB larvae populations within known infested areas.
The purple prism, the purple and green multifunnel traps, and branch sampling yielded no EAB outside of the known infestation in Hassleroth Park. Though unsuccessful at detecting EAB, the trap placed at Hasselroth Park yielded 12 adult EAB beetles while the branch surveys found 13 larvae in Larval density in sampled branches averaged 3.2 larvae per 50cm branch. There was no relationship between larvae densities and ash canopy rating (p = .502), exit holes (p = .782), epicormic shooting (p = .162), bark splitting (p = .152), or branch diameter (p = .388).
Methods: Branch Survey
A total of 11 ash trees were sampled between August 2014 and September 2014 while 21 ash trees were sampled between July 2015 to August The species, DBH, ash canopy rating, exit holes, bark fissures, and epicormic shooting were assessed for each survey. One to two live branches were cut from the middle crown at the base using a pole saw. Branches were then cut 50cm from the base, and these sections were used to conduct the survey. Samples were whittled in 1mm thick strips until the cambium was reached (Figure 3). The number of larvae, the instar level, and galleries found within each sample was recorded, while EAB larvae were collected using forceps, vials, and 70% ethanol (Figure 4). The relationship between larvae densities and DBH, ash canopy rating, exit holes, bark splitting, and epicormic shooting were assessed using linear regression (alpha value = 0.05).
Figure 6. Hasselroth park is located in Rock Island, IL
Figure 5. All of the Ash Trees in Rock Island IL are indicated by a red marker. The blue marker is the location of Augustana College
Methods: Trapping Survey
Figure 1. An Emerald Ash Borer (Agrilus planipennis Fairmaire)
The cities of Rock Island and Moline, IL were divided into square mile quadrats with a 2 mile buffer established around Hasselroth Park (Figure 2). Trap set up occurred between June and June One prism and one funnel trap were spaced throughout each quadrat when possible, totaling 63 traps throughout the cities. Three multifunnel traps were set within in the 2 mile buffer as a control. During each trap set-up, the land use, species, diameter at breast height (DBH), ash canopy rating, bark splitting, and epicormic shooting were recorded. Manuka oil and z-3-hexonal lures were attached to each trap at the beginning of the survey and changed once after 30 days. Traps were hung from ash trees using sturdy twine or rope. All traps were taken down between August and August Traps were checked every two weeks.
Discussion
The low success rate of detecting the presence of EAB utilizing traps in 2014, with Hasselroth being the only exception, led us to rely strictly on branch surveys. Using poll saws was very cost prohibited and required a lesser time period to retrieve data.
One suspected reason why EAB did not spread within the past two years can be due to the geographical barrier of the Mississippi River.
Last years study also collected stem surveys, thus creating a lower availability of accessible (less than 10 feet high) Ash tree branches for this years research. Lowering the number of expected samples, visual assessment was completed on larger trees (more than 10 feet high), looking at the presence of EAB holes, overshoots, and bark fissures.
Branch sampling at Hasselroth Park determined the presence of high larval densities. In the summer of 2014 it was predicted that EAB larva would have a higher density within the next year. Our data shows no significant change in the spatial distribution or density of EAB within the city of Rock Island.
The large amount of larvae resident in Hasselroth park limits the amount of time city managers and residents have to prepare for the invasion front. It is noted that EAB has the potential to cause not only ecological damage, but billions of dollars of economic damage (DeSantis et al. 2015).
Figure 3. The samples were whittled to reveal the cambium and serpentine galleries
Figure 4. The EAB larva in the primary development stage of Instar 1
References
DeSantis R, Bartlett M, Vermunt B, Moser W, Gormanson D. Effects of climate on emerald ash borer mortality and
the potential for ash survival in North America [electronic resource]. Agricultural And Forest Meteorology [serial online]. September 15, 2013; : Available from: Agricola, Ipswich, MA. Accessed October 12, 2015.
Persad A, Tobin P. Evaluation of Ash Tree Symptoms Associated with Emerald Ash Borer Infestation in Urban Forests. Arboriculture & Urban Forestry [serial online]. March 2015;41(2): Available from: Academic Search Complete, Ipswich, MA. Accessed October 12, 2015.
Siegert N, McCullough D, Liebhold A, Telewski F. Dendrochronological reconstruction of the epicentre and early spread of emerald ash borer in North America. Diversity & Distributions [serial online]. July 2014;20(7): Available from: Academic Search Complete, Ipswich, MA. Accessed October 12, 2015.
Acknowledgments
This research project was conducted in coordination with The Upper Mississippi Center. We thank Dr. Michael Reisner for his help in protocol development, data collection and availability to a truck. We would also like to thank our fellow interns at the UMC for aiding in branch samples and whittling the wood; Daniel Herrera, Megan Lipke, Diana Schultz, and Jacob Torres. We would finally like to thank Dr. Tierney Brosius for the generous use of her lab, as well as Mr.Brosius for fixing our pole saws.