Emerald Ash Borer

Dennis Ring  |  9/3/2018 10:45:24 PM

The emerald ash borer is an invasive metallic wood boring or flat headed wood boring beetle (family Buprestidae) that kills species of North American ash trees.The emerald ash borer was introduced into the United States from Asia and detected in 2002.This insect has killed 99% of the ash trees with a diameter greater than 1 inch in the area of its original introduction (southeast Michigan).All species of North American ash trees that the beetle has come in contact with have been susceptible to attack from the emerald ash borer.Death of blue ash has been less than death of white, green, and black ash.It is possible that North American ash trees may be eliminated from the continent by the emerald ash borer.

Olive trees (Olea europea) have been reported as a new host of emerald ash borer.This is the second non-ash host of this insect.White fringe trees (Chionanthus virginicus) are the other non-ash host.This will impact people growing olive trees as the beetle expands its range.

The emerald ash borer was discovered in southern Arkansas in 2014.It was discovered in 2015 infesting ash trees in Webster Parish, Louisiana.In 2016 it was found infesting ash trees in Bossier, Claiborne, Lincoln, and Union parishes.Now it has been detected infesting ash trees in four more Louisiana parishes:Bienville, Caddo, Jackson, Morehouse, and Ouachita. These ten parishes are quarantined by the Louisiana Department of Agriculture and Forestry.Ash trees are particularly important along waterways and provide conditions on the banks of waterways that protect fisheries and reduce erosion.

The emerald ash borer is native to NE China, Korea, and Russia.In these locations it attacks stressed, weakened, or dying treesIt was established in southeast Michigan by the early 1990s, and China is believed to be the likely source of the infestation. The beetle was probably imported in crating, pallets, or dunnage made from infested ash.

D-shaped exit holes (2–3 mm in diameter) are left in the trunk and branches by the emerging adults. This is different from other species of metallic wood boring beetles in North America which have oval exit holes.Adult beetles live from 3–6 weeks.The average number of eggs produced per female beetle is 40 - 70 eggs, but 200 eggs may be produced.

The female lays eggs one at a time in crevices or bark cracks or beneath bark flakes.Larvae emerge from eggs in two weeks. The upper part of the tree is attacked before the main trunk is attacked.Thus, early infestations may go unnoticed quite easily.Once larvae hatch they bore into the tree and start making galleries and feeding. The galleries are serpentine in shape, and they eventually girdle the tree killing it.Infested trees die back and have sprouts at the base of the tree.

Infested trees die in 2–4 years. The larvae go through four instars and feeding occurs in mid-summer through fall. The larvae pupate in mid to late spring with adult emergence following shortly thereafter.The life cycle may take one to two years.

Emerald ash borer adult beetles move short distances through flight, and females may fly about one half a mile.The range of long distance flight of these beetles is unknown.The major way the insect spreads is through movement by humans:firewood, branches, limbs, ash trees, untreated ash lumber or logs with bark attached, ash chips that have not been composted and ash bark chips (not composted) greater than 1 inch in two dimensions.It is extremely important that these items not be moved in order to reduce the spread of emerald ash borer!The quarantine procedures should be followed.In particular, potentially infested firewood should not be transported outside of quarantine areas.

It is expected that this insect will continue to expand its range in Louisiana.In preparation for the arrival of the emerald ash borer, the location of ash trees may be determined and the trees protected aggressively by using systemic insecticides.Biocontrol efforts are ongoing and parasites may be released in attempts to reduce the numbers of emerald ash borers.Additionally, ash trees in poor health may be removed.

Inconsistent results have been obtained from insecticide trials. Systemic insecticides have given the best results.Applications may be (a) as soil drench or injection, (b) injections in the base of the trunk, or (c) sprays on the bottom 1.5 m of the trunk. Three years of approximately 100% protection have been obtained using Emamectin benzoate in some trials. Other systemic insecticides include Imidacloprid 2F, 75 WP or WSP; and Dinotefuran 20 SG, 70 WSP.

Much of the information in this article was summarized from the following publication.

Daniel A. Herms, and Deborah G. McCullough.2014.Emerald Ash Borer Invasion of North America: History, Biology, Ecology, Impacts, and Management.Annual Review of Entomology.Vol. 59: 13-30.

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