Emerald Ash Borer (Agrilus planipennis) is an extremely destructive species of wood-boring beetle native to Southeast Asia. EAB is believed to have been accidentally introduced to North America in the 1990s by hitchhiking from Japan in wood-packing materials aboard a cargo ship destined for Detroit, MI. Due to the aggressive nature of EAB, not one of the 7.5 billion native ash trees present in the United States is considered safe. Unless the path of EAB is averted, the four different species of ash native to northwest Indiana may soon become endangered.
A classic "S"-shaped gallery made by an EAB larva during development.
EAB uses ash trees as a food source in its adult stage, and as both a food source and shelter in the larval stage as it burrows under the bark, eating the critical vascular tissue called phloem. Phloem (pronounced ‘flow – um’) is responsible for transporting “food” in the form of carbohydrates from the leaves to the roots. Developing larva of EAB create “S”-shaped burrows called galleries immediately under the bark of the host tree. It is this action, known as girdling, that kills the tree. Once a tree is infested, it will almost certainly die within two to three years.
Our native ash trees show little of the resistance present in the ash trees native to EAB’s home of Southeast Asia. Those native trees possess the ability to quickly form healthy callus tissue over wounds created by burrowing, which minimizes the damage and loss of connectivity between the root system and the canopy of the tree. EAB is not the enormous threat in Asia that it is here in North America because the ash trees there have co-evolved with the pest, adapting to new changes and never allowing the insect to gain the upper hand. However, this is not an option for our native ash as evolution can take hundreds of generations, while EAB has moved thousands of miles and destroyed 30 million ash trees since it was discovered in Michigan in 2002.
When EAB larva emerge as adults, they form a sideways D-shaped exit hole.
A handful of hopeful solutions has been found to stem the EAB infestation. It is possible to prevent infestation of prized specimens along streets or in yards using specific pesticides applied to the soil near a tree or by injection directly into the trunk. However, use of pesticides becomes extremely expensive and logistically impractical when applied to even a small forest of ash trees and offers little assistance once a tree is infested. If you have an ash tree in your yard that you want to protect here in LaPorte County, pesticides are your only option. Contact an ISA Certified Arborist: (http://www.isa-arbor.com/findArborist/findarborist.aspx) to prevent infestation. Once a tree is infested, it is probably too late.
Another possible solution being extensively studied is the use of parasitic wasps that lay eggs in the larva of EAB, killing them before they can become adults and reproduce. This method of biological pest control has severely backfired in other cases (see: cane toads in Australia). However, parasitic wasps are seldom seen and are harmless to humans. Researchers have collected parasitic wasps native to Southeast Asia. In the summer of 2007, small populations of these wasps were released in tests in Michigan, Indiana and Ohio to see if they can slow and control the spread of EAB across the United States.
Although EAB has not yet been discovered in LaPorte County, it probably has at least some presence here since it has been discovered in St. Joseph County to the east, Porter County to the west and Berrien County to the north.
The City of LaPorte hosts very few ash trees on public or private property. If you think you have an insect infestation in your ash tree this spring, contact the LaPorte Forestry Department at (219) 326-9600.
VISIT THESE WEBSITES to see pictures of telltale signs of Emerald Ash Borer infestation:
— Find pictures of great examples of infestation at the Purdue University site: http://extension.entm.purdue.edu/eab/
— Pictures of EAB imposters and infestation at the University of Wisconsin site: entomology.wisc.edu/emeraldashborer/
— Regulatory and quarantine information can be found at the DNR website: http://www.in.gov/dnr/entomolo/3443.htm
KEITH O’HERRIN is the City Forester for the City of LaPorte. He can be found at the Park and Recreation Office at 250 Pine Lake Ave. or reached at 326-9600.
The Emerald Ash Borer is about 3/8" long, making it difficult to detect where it feeds on leaves high in the canopy.
