The Emerald Ash Borer (EAB) has killed millions of ash trees since its discovery in southeastern Michigan in 2002.  Native to Asia, this insect was probably introduced to the United States in wood packing material carried in on cargo ships or airplanes.  Through a combination of natural spread and human activity it is now found in Michigan, Ohio, Indiana, Illinois, Missouri, Pennsylvania, Maryland, West Virginia, Virginia, Wisconsin, Kentucky,  and now Minnesota, placing millions of additional ash trees at risk.  It will continue to spread.

Adult beetles feed on leaves and it is uncertain what impact adult feeding has on tree health.  Larvae, on the other hand, feed on the inner bark and disrupt the movement of water and minerals within a tree causing eventual dieback, decline, and death of the tree. Symptoms of early infestations may be difficult to diagnose.  Be on the look-out for multiple declining ash in a given area.  As infestation progresses, small vertical splits in the bark can be seen on twigs or trunk and woodpecker holes may be present on trees. Trees may die after 2-4 years or less (small trees).

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Symptoms

* Symptoms of early infestations may be difficult to diagnose
* As infestation progresses, small vertical splits in the bark can be seen on twigs or trunk
* Typically the top 1/3 of crown dies first and works its way down the tree (photo)
    o Trees appear to lose about 30%-50% of their canopy after 2 years of infestation.
    o Trees may die after 2-4 years or less (small trees)
* As the top of the tree continues to decline epicormic shoots form (photo)
    o Epicormic shoots can arise at the interface between healthy and dead tissue anywhere in the canopy
* Be on the look-out for multiple declining ash in a given area
* As infestation progresses, woodpecker holes may be present on trees
* Distinct “S” shaped frass filled larval galleries that score the outer sapwood and phloem underneath the bark
    o Galleries in an affected area can range from 4-20 inches in length
    o Galleries from an individual larvae become progressively wider as the larvae grows
* D-shaped exit holes
    o (generally present after an infestation has been present for 1 yr. or more)
    o Approximately 1/8 inch in diameter
* Dense root sprouting may occur after death of a tree
* Leaf symptoms from adult feeding is usually displayed in small irregular shaped patches along the leaf margins

Signs of EAB
Adults
* Usually bronze or golden green with dark metallic emerald green wing covers
* Adults are slender and can be 1/4 inch to 1/2 inch in length
* Top of the abdomen under the wings is metallic purplish red (seen when wings are spread)
* Adults may be difficult to detect even in areas of high infestation
    o Short period of activity (3-6 wks of activity)
    o Generally active during the day (sunny and warm days)
    o Adults will hang out in bark crevices or on foliage during rain, heavy cloud cover, high winds, or when temps reach above 90 F.
* Adults can be found most years beginning from late May into Mid-August
    o Peak Mid to Late June
* EAB has distinct features, but it can be confused with the following beetles:
    o Banded Ash Borer, Japanese Beetle, Six-Spotted Tiger Beetle, Bronze Birch Borer, Two-lined Chestnut Borer, Caterpillar Hunter

Larvae
* Slender, flattened, segmented (10 total abdomen segments) cream colored larvae with a brown head can be found by peeling back loose bark on infested trees
* Larvae range in size from 1 -1 1/4 inches in length
* Pincer-like appendage on the last segment
* Larvae hatch from eggs deposited in bark crevices (photo?)
* Larvae chew through the bark and begin feeding on phloem
* Feeding is completed in autumn and pre-pupal larvae over winter in the outer sapwood or bark.
* Pupation begins in late April or May
* Newly formed adults will often remain in pupal chamber for 1-2 wks prior to emergence in late May into Mid-August
* Some larvae may require a second year of maturation feeding prior to emerging the following year as adults

Hosts
* Green Ash (Fraxinus pennsylvanica), White Ash (F. Americana), Black Ash (F. nigra) and Blue Ash (F. quadrangulata) cultivated varieties.
     o Order of susceptibility: Green Ash, Black Ash, White Ash, Blue Ash
* All will be attacked if beetle populations are high enough
* Some evidence to suggest that green ash may be preferred over other species
* ‘Autumn Purple’ White Ash has shown more tolerance to EAB than ‘Marshall Seedless’ green ash in trials by Smitley
* EAB can infest ash trees as small as 1 DBH inch up to the largest specimen trees
    o Stress may contribute to the vulnerability and speed that a tree declines from EAB
    o EAB has also killed seemingly vigorous trees growing under optimum conditions  (especially as beetle densities build)

Insecticide Treatment Considerations for EAB
General Considerations
* What is the value of the ash tree to the homeowner?
* Ensure that the homeowner understands that to fully protect their tree for the long term they must treat their ash tree annually for an indefinite period of time
    o Treatment must continue indefinitely or until the EAB no longer poses a risk.
    o In Michigan ash trees that are not protected in certain areas have been killed over a 4-8 year period. EAB pressure may decrease once unprotected ash trees are no longer present.
* Preventive treatments with soil applications of Xytect 75 WSP or Xytect 2F provide greater likelihood for success than treatments on infested trees
    o Recognize that it is difficult to detect the presence of EAB during the early stages of infestation.
* When symptoms are present, the tree has been infested for up to several years and the chance of saving it decreases.  Trees with up to 50% symptoms have been saved.  However, treating infested trees carries higher risk of failure.
* Ash trees may be protected from EAB by applying Xytect to trees prior to the onset of visible symptoms.
* Annual applications of Xytect are required for continued protection.  If applications cease, trees will become susceptible to the pest.
* Arborists must discuss the following with client’s that reside in eradication or quarantine areas.

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