Emerald Ash Borer

The native range of the emerald ash borer is temperate north-eastern Asia, which includes Russia, Mongolia, northern China, Japan, and Korea. The beetle is invasive in North America, where it has a core population in Michigan and surrounding states and provinces. Populations are more scattered outside the core area, and the edges of its known distribution range north to Ontario, south to northern Louisiana, west to Nebraska, and east to New Brunswick. Satellite populations exist in Colorado and in the Pacific Northwest in Oregon. In eastern Europe, a population was found in Moscow in 2003. From 2003 to 2016, this population has spread west towards the European Union at up to 40 km (25 mi) per year and is expected to reach central Europe between 2031 and 2036. Although not recorded from the European Union as of 2019, it has already spread to far eastern Ukraine from neighboring Russia. In 2026 Hungarian authorities collected two adult specimens in a pheromone trap.

The emerald ash borer life cycle can occur over one or two years depending on the time of year of oviposition, the health of the tree, and temperature. After 400–500 accumulated degree-days above 10 °C (50 °F), adults begin to emerge from trees in late spring, and peak emergence occurs around 1,000 degree-days. After emergence, adults feed for one week on ash leaves in the canopy before mating, but cause little defoliation. Males hover around trees, locate females by visual cues, and drop directly onto the female to mate. Mating can last up to 50 minutes, and females may mate with multiple males over their lifespans. A typical female can live around six weeks and lay around 40–70 eggs; females that live longer can lay up to 200 eggs. Eggs are deposited in bark crevices, flakes, or cracks and hatch about two weeks later. Eggs are roughly 0.6 to 1.0 mm (0.02 to 0.04 in) in diameter, and are initially white, later turning reddish-brown if fertile. After hatching, larvae chew through the bark to the inner phloem, cambium, and outer xylem, where they feed and develop. Emerald ash borers have four larval instars. By feeding, larvae create long, serpentine galleries. Fully mature fourth-instar larvae are 26 to 32 mm (1.0 to 1.3 in) long. In fall, mature fourth-instars excavate chambers about 1.25 cm (0.49 in) into the sapwood or outer bark where they fold into a J-shape. …

French priest and naturalist Armand David collected a specimen of the species during one of his trips through Imperial China in the 1860s and 1870s. He found the beetle in Beijing and sent it to France, where the first brief description of Agrilus planipennis by entomologist Léon Fairmaire was published in the Revue d'Entomologie in 1888. Unaware of Fairmaire's description, a separate description naming the species as Agrilus marcopoli was published in 1930 by Jan Obenberger.