emerald ash borer (EAB)

Emerald ash borer was first detected in Moscow, Russia in 2003. Since then, it has continued to spread west. It is expected to reach central Europe between 2031 and 2036.

On October 8, 2003, the USDA Forest Service imposed a quarantine on emerald ash borer. It prohibited the interstate movement of all firewood and other regulated items out of infected areas. The USDA removed the quarantine effective January 14, 2021. An emerald ash borer female can fly up to 100 miles in her lifetime. The quarantine had not been effective in preventing the spread of the beetle into adjacent areas.

On November 1, 2023, the Minnesota Department of Agriculture declared a quarantine to prevent the further spread of emerald ash borer. It prohibits the importation of firewood and other regulated articles into the state, and the movement of those articles from quarantined areas to uninfected areas.

Emerald ash borer, also known by the acronym EAB, is an exotic, invasive, small to medium-sized, metallic wood-boring beetle. It is native to northeastern Asia, including China, Mongolia, North and South Korea, Japan, Taiwan, and far eastern Russia.

Emerald ash borer was first detected in North America in 2002 in Detroit Michigan. It was probably imported in the wood of a shipping crate in the late 1990s. It has spread rapidly since its introduction. It now occurs from Maine to northern Georgia, west to Minnesota and northeastern Texas. It was discovered for the first time in Minnesota on May 14, 2009, in South Saint Anthony Park in St. Paul. It is now common in southeastern Minnesota, and it is continuing to spread in the state. Eight infected counties were added in 2023 and six infected counties were added in 2024.

Emerald ash borer larvae feed exclusively on black ash, green ash, and white ash. They feed on the inner bark (cambium), creating serpentine tunnels (galleries) that interrupt the flow of food. They eventually girdle and kill the branch or tree. They have killed tens of millions of trees in the eastern United States, including over five million trees in a 3,000 square mile area of Michigan.

Adults are active in Minnesota from May 1 through September 30. They are found in deciduous forests and woodlands, in parks, and in urban and residential areas, anywhere ash trees are found.

Adults are 5⁄16″ to 9⁄16″ (7.5 to 14 mm) in length. Males are smaller than females. The body is bullet shaped – rigid, narrow, and elongate. It is bright emerald green overall, with varying amounts of coppery, red, or gold metallic reflections. Rarely individuals may be bluish or reddish. The amount of metallic reflection varies with the angle and strength of the light, so that the overall color can change as the observer shifts positions.

The head is flat and is slightly tucked beneath the first segment of the thorax (prothorax). The eyes are black and kidney shaped. The antennae are short and have 11 segments. Segments 1 through 3 are cylindrical. Segments 4 through 11 are sawtoothed. The mouthparts are projected downward.

The upper plate covering the prothorax (pronotum) is wider than long. It is usually bright green with both yellow and coppery or bronze reflections. On the underside of the male there is fine, pale, erect hair over the entire thorax. The female does not have that hair.

The wing covers (elytra) are colored similar to the pronotum but are usually darker and greener.

The upperside of the abdomen is bright metallic red. EAB is the only Agrilus species in North America with this feature. The underside of the abdomen is also red. It is only visible when the elytra and hindwings are raised. In the male, there is a well-developed raised ridge (carina) on the underside of the last abdominal segment. The carina continues as a short spine at the tip of the abdomen.

Total length: 5⁄16″ to 9⁄16″ (7.5 to 14 mm)

Deciduous forests and woodlands, in parks, and in urban and residential areas, anywhere ash trees are found

May through July

The larvae overwinter in the tree. They take one or two years to mature, depending on the temperature. Adults chew their way out in the spring, leaving a characteristic ⅛″ (3 mm) wide, D-shaped hole.

Cambium of black ash, green ash, and white ash

The larvae feed on the inner bark (cambium), creating serpentine tunnels (galleries) that interrupt the flow of food. They eventually girdle and kill the branch or tree. They have killed millions of trees in the eastern United States, including over five million trees in a 3,000 square mile area of Michigan.

Woodpeckers consume large numbers of EAB larvae, and they are the most effective biological control agents.

Native parasitic wasps can parasitize EAB larvae, but they usually kill less than 5% of the larvae on an infected tree.

Four parasitic wasp species from Asia have been introduced into North America in an effort to manage EAB: Oobius agrili, Tetrastichus planipennisi, Spathius agrili, and Spathius galinae.

Sources

22, 29, 30, 82.

Animal and Plant Health Inspection Service, U.S. Department of Agriculture, Emerald Ash Borer

Minnesota Department of Agriculture, Interactive EAB Quarantine Map

Minnesota Department of Natural Resources, Emerald ash borer (EAB)

Common

Emerald Ash Borer Agrilus planipennis

Agrilus planipennis, emerald ash borer, Milwaukee, WI. Photo was taken on June 16, 2017. The year the photo was taken was one of the first years I saw this beetle.

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Location: Milwaukee, WI

Agrilus planipennis, emerald ash borer, Milwaukee, WI. Photo was taken on June 16, 2017. The year the photo was taken was one of the first years I saw this beetle.