Tree species diversity and the rate of infestation by the emerald ash borer, Agrilus planipennis, in the greater Garden City area of Long Island, NY Sanaa Khan and Lisa Filippi
The emerald ash borer (EAB), Agrilus planipennis Fairmaire, has been known to cause mayhem amongst trees in communities since its discovery. Specifically, the beetle burrows into the bark of the Fraxinus genus of trees, commonly known as ash trees. Though the burrowing itself doesn’t cause substantial damage to the tree, the EABs subsequent act of laying larvae results in the epidemic we witness in towns such as Garden City, NY. The larvae of the EAB feed upon the cambium layer, the soft inner bark, of the ash tree, tunneling under the surface of the trunk. This results in reduction of the ability of the ash tree to absorb water and nutrients and its eventual death. Areas with a high concentration of ash can promote the spread of the EAB, as can the transport of infected firewood. The town of Garden City, amongst many other towns on Long Island, have an abundance of ash trees which have left them susceptible to the effects of this invasive species. The purpose of this study is to analyze the effect of tree species diversity on the rate of infestation by the EAB in the greater Garden City area of Long Island, NY. The town of Garden City has already begun the planned removal of up to 1000 ash trees which not only have aesthetic impact on the neighborhood but, economic and environmental ones as well. It is hypothesized that a higher density of ash trees will result in higher infestation rates by the EAB.
METHODS:
Mapping
• Google Maps/ satellite imaging utilized to map 100 m segments of streets proposed by the town of Garden City to be part of removal plan, measurements were confirmed upon on-site surveys. • Streets included: Washington Ave, Nassau Blvd (2), Franklin Ave, Stewart Ave, Clinton Rd (2), Main Ave and Meadow St.
Recording Diversity and Infestation
• Counts of ash trees and total trees were taken. • Presence of Infestation observed through noting burrowing holes and overall health of trees.
Simpson’s Diversity Index
Survey of Residents
• Simpson’s Diversity Index (D) was utilized to calculate tree diversity. • Simpson’s Diversity Index was subtracted by 1 in order to gain a more logical numerical depiction of the diversity value. • Pearson’s Correlation Coefficient and two-tailed t-test were run.
The rate of infestation by the emerald ash borer significantly increased when an increase in ash tree density was observed (Fig. 1). The beetle's ability to migrate from one host tree to the next emphasizes the importance of maintaining tree diversity in neighborhoods such as these. Though upon planting these trees, the idea of beauty in symmetry was prioritized by the town, the lack of prior ecological and behavioral research has resulted in a major set back both aesthetically and economically.
• 50 Property owning residents were surveyed including: • Awareness of situation and city’s plan • Awareness of ash tree/EAB presence on their property • Willingness to take action and if so, treatment vs removal • General feelings towards aesthetic, environmental and economic impact
RESULTS:
Survey results from citizens of Garden City portrayed a lack of awareness of the town’s plan of action. However, once they were aware, there was a strong willingness to take action in preserving their own properties’ tree diversity as well as economic value (Fig. 2).
21 R² = 0.6941 p = 0.0053
18 15
f(x) = − 16.27 x + 16.61
12 9
CONCLUSION:
6 3 0 0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Diversity of Trees (1-D) Figure 1. The effect of tree diversity calculated by Simpson’s Diversity Index on EAB infestation rate, (two segments taken for Clinton and Nassau). A greater diversity of trees resulted in decreased rates of infestation (Pearson’s Correlation Coefficient, p = 0.0053).
The emerald ash borer (EAB), Agrilus planipennis Fairmaire (1).
Believe trees add economic value to property? Would cut tree without treating first?
Aware of ash tree on property? Aware of EAB situation? 0%
In areas where a higher density of ash trees were located, infestation rates by the emerald ash borer were significantly higher (Fig. 1). Though towns such as Garden City are taking active efforts to stop the spread of this beetle, future strategies for planting of new trees by the town as well as property owners should prioritize tree diversity in their plans. Moreover, an outreach program to educate the public about the ecological and economic value of maintaining a healthy amount of diversity when planting trees should be implemented. REFERENCES:
Willing to take action?
10%
20%
Yes
The distinctive half moon or “D” shaped burrow hole (2,3).
EAB tunneling (3).
DISCUSSION:
Infested Ash Trees
INTRODUCTION:
30%
No
40%
50%
60%
70%
80%
90%
100%
Somewhat
Figure 2. Survey of property-owning residents on awareness, action and effect. Awareness was low, but a willingness to take action was high.
1. Gast, R. (2021, July 28). Emerald Ash Borer Solution? parasitic Wasps. News, Sports, Jobs - Adirondack Daily Enterprise. 2. City of Salem. (n.d.). Emerald Ash Borer. Retrieved December 2, 2022, from https://www.cityofsalem.net/community/natural-environmentclimate/trees-and-plants/emerald-ash-borer. 3. Obermeyer, J. (2018). EAB Identification Retrieved December 2, 2022, from https://extension.entm.purdue.edu/EAB/Identification.html