The Emerald Ash Borer (EAB) is a newly discovered non-native insect pest of American ash trees. In July 2002, it was identified in southeastern Michigan and may have been in Michigan for as long as five years. Ash trees were a popular landscape tree during the 1960s, 70s, and 80s. Today however, it is not advised to plant new ash trees.
The EAB is a beetle from Asia and it has been assigned the scientific name Agrilus planipennis.
The emerald ash borer lays eggs in small groups that bury themselves into the ash tree bark after hatching. The larvae gnaw at layers beneath the tree's bark, cutting off the tree's nourishment. The larvae can girdle and kill just branches or the entire tree.
It is not clear why some of the larvae take only 1 year to hatch as adult beetles, and others can take 2 years to complete the cycle. Once emerging from the ash tree as adults, the beetles survive for about 2 weeks or so during which time they mate and the life cycle repeats. Adults begin to emerge from the ash tree in May and June.
Emerald Ash borer appears to infest all types of ash trees. In its native range, it is also known to infest Asian walnut and elm species. This insect can kill trees quickly, but often it goes undetected for several years before damage becomes apparent. A confounding factor in looking for this pest is that ash trees have been showing symptoms of decline for more than 25 years.
There is also a native ash borer to contend with. The banded ash borer and the ash/lilac borer are common pests of stressed ash trees. Both are clearwing moths, and the larvae produce larger, rounded exit holes, compared to the small (3-4 mm) D-shaped exit hole left by emerging adult emerald ash borers.
Besides the D-shaped exit holes found on the bark of infected trees, other evidence of emerald ash borer includes frass-filled larval tunnels in a serpentine pattern in the outer sapwood and phloem of the trunk and branches and 5-10 cm vertical splits in the bark above these larval galleries.
Once the adult emerald ash borer emerges from the tree, it can travel about a half-mile in search of another ash tree. It can also cover greater distances if the beetle happens to become attached to a moving automobile.
Officials say the borer's expanding range is most likely caused by human intervention. Ash tree firewood carries the larvae. Campers buy the firewood from infected areas, then move on to an un-infected area and leave the firewood at the campsite when they leave. It is important not to transport firewood from camp site to camp site.
The federal government allocated about $20 million to fight the borer in 2005 compared to about $38 million in 2004.
Read also: Identifying Emerald Ash Borer infestation
Treatment can be through surface spray, mauget injections, or systemic treatments. Relatively new treatments can provide 100% survival on treated trees if the particular tree still has at least a 50% canopy in place at time of treatment. The EAB does not seem to infect or damage saplings smaller than about 2" in diameter. It is possible that the smaller tree size does not provide enough protection for the larvae to survive winters.
Inspect your ash trees for signs of damage—D shaped exit holes, thinning crown, and dead limbs.
While many believe the only preventative method for stopping the spread of the Emerald Ash Borer is to clear-cut trees, there is another alternative. Recent Michigan State University (MSU) research, conducted in conjunction with the USDA, confirmed Imicide® and Inject-A-Cide B® from the J.J. Mauget Co. are effective for the control of the Emerald Ash Borer.
Mauget’s enclosed micro infusion system works from the inside out, so it’s sensitive to the environment and less harmful to the tree.
Any professional applicator can be trained to use Mauget’s micro-infusion technology, which only requires a power drill, gloves, tape measure, rubber mallet, protective eyewear, and Mauget’s feeder tubes and capsules.
Untreated trees and areas with infestations will see ever higher death rates of the ash trees. The reason for this is that adult female EABs give off a pheromone that attracts males to the area thus increasing the EAB populations until all of the ash trees have been devastated and the EAB no longer has a source to incubate their eggs.