Agrilus planipennis, commonly known as the emerald ash borer, is a green buprestid or jewel beetle native to northeastern Asia that feeds on ash species. This Asian insect was likely transported in wood crates, pallets and other packing material which was shipped to the United States in the mid-1990s, according to Michigan State University Extension (MSUE). The Emerald Ash Borer is responsible for the destruction of tens of millions of ash trees in 27 states. In its native range, it is typically found at low densities and does not cause significant damage to trees native to the area. Outside its native range, it is an invasive species and is highly destructive to ash trees native to northwest Europe and North America.
EAB populations can quickly rise to damaging levels. Host species include green ash, white ash, black ash, blue ash, and pumpkin ash. After initial infestation, all ash trees are expected to die in an area within 10 years without control measures. Every North American ash species shows susceptibility to EAB as North American species planted in China also shows high mortality due to EAB infestation.
Signs and symptoms are indicators of insect attack. A sign is a physical damage to a tree, such as a gallery, a hole, or a feeding notch in the leaf, resulting from the attack by an insect. A symptom is a tree’s response to insect attack and includes premature yellowing of foliage, dead branches, thinning crowns, or bark cracks. Crown dieback is one common symptom of EAB infestation. Dieback of the upper and outer crown begins after multiple years of Emerald ash borer larval feeding. Trees start to show dead branches throughout the canopy, beginning at the top. Larval feeding disrupts nutrient and water flow to the upper canopy, resulting in leaf loss. Leaves at the top of the tree may be thin and discolored. Let us look at another symptom known as Epicormic Sprouting. When trees are stressed or sick, they try to grow new branches and leaves wherever they still can. Trees may have new growth at the base of the tree and on the trunk, often just below where the larvae are feeding. Woodpeckers, on the other hand, eat emerald ash borer larvae that are under the bark. This usually happens higher in the tree where the emerald ash borer prefers to attack first. If there are large numbers of larvae under the bark the woodpecker damage can make it look like strips of bark have been pulled off of the tree. This is called “flecking.”
Now let us have a look at the signs of infestation done by an emerald ash borer.
D-shaped emergence holes: As adults emerge from under the bark they create a D-shaped emergence hole that is about 1/8 inch in diameter.
S-shaped larval galleries: As larvae feed under the bark they wind back and forth, creating galleries that are packed with frass (larva poop) and sawdust and follow a serpentine pattern.
Larvae: Larvae are cream-colored, slightly flattened (dorso-ventrally) and have pincher-like appendages (urogomphi) at the end of their abdomen. Larvae are found feeding beneath the bark.
Adults: Adult beetles are metallic green and about the size of one grain of cooked rice (3/8 – 1/2 inch long and 1/16 inch wide). Adults are flat on the back and rounded on their underside.
Here are some recent news articles pertaining to the damage caused by the EAB.
Public is paying price of emerald ash borer infestation
April 19, 2017, USA
OSCODA – High winds sweeping through Iosco County this month have toppled trees on top of power lines, causing electrical outages and home damage.
Most of the felled trees are dead or dying ash trees, killed by emerald ash borers (EAB), an invasive insect which was discovered in southeastern Michigan and Windsor, Ontario in June 2002.
“Municipalities and homeowners are paying for the EAB invasion,” said Eric Brandon, Alcona Conservation District forester for Alcona and Iosco counties.
EAB are so aggressive that ash trees die within two or three years after becoming infested. Damage is caused by the larvae, feeding in S-shaped tunnels on the inside of bark of branches and tree trunks. It is the inner bark, or phloem, which transports nutrients and water.
Emerald ash borer destroying Door Co. trees
April 11, 2017, USA
Thousands of ash trees are dying as the emerald ash borer eats its way up the Door County peninsula. One of the hot spots for the disease is the downtown of the city where chunks of bark lie under the ash trees and woodpeckers are feasting on the emerging tiny insects.
More than 12 million ash trees throughout the county are at risk since the emerald ash borer bugs were found near Fish Creek and in Sturgeon Bay in 2014. Ash trees account for about 13 percent of the county’s estimated 115 million trees, said Bill Ruff, a forester for the state Department of Natural Resources in Door and Kewaunee counties.
There are a variety of treatment options that can serve as a control measure for the EAB, but they are not a cure.
Insecticides with active ingredients such as imidacloprid, benzoate, and dinotefuran are currently used. These insecticides are toxic in nature. They kill the target as well as the non- target species. They are harmful to human health as well.
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