Insects · Coleoptera · Buprestidae

Emerald Ash Borer

Agrilus planipennis

Not Evaluated

It has not yet been assessed against the IUCN criteria. See full glossary

Agrilus planipennis is a beetle native to north-eastern Asia belonging to the family Buprestidae. It is known by the common name emerald ash borer, which alludes to its bright green colouring and to its diet of various ash species. Females of this species lay eggs in the cracks in ash bark, and the larvae feed beneath the bark before emerging as adults in one or two years. Within its native range it generally occurs at low densities and does no significant damage to the trees native to the area. Outside its native range it is regarded as an invasive species and as highly destructive to the ash trees native to north-western Europe and North America. Before it was found in North America very little was known about the emerald ash borer; as a result, much of the research on its biology has focused on North America. Local governments in North America are trying to control it by monitoring its spread, diversifying tree species, and using insecticides and biological control.

Size

up to 1.3 cm

Lifespan

1 years

Diet

Herbivore

Feeds mainly on plants.

Activity

Diurnal

Active mainly during the day.

Social structure

Solitary

Lives and hunts alone, joining others only to breed.

Sighting difficulty

Unknown

Temperate forestHerbivore Diurnal Solitary Insect Temperate forest

10countries1same family

Fun facts

The adults' exit holes have an unmistakable D shape, and they are often the first proof that a tree has already been infested for years.
In its native forests, in China and Korea, it is a rare and unimportant insect: it is the American and European ash trees that have no defences against it.
It spreads above all through the movement of firewood, which is why many North American regions ban moving firewood between counties.
It is one of the most destructive invasive forest species in history. It was detected near Detroit in 2002 and has killed hundreds of millions of ash trees in North America.
By the time it was discovered it had been established for a decade: dendrochronological analyses showed it was already killing trees in Michigan in 1998, and it probably arrived in the early 1990s in wooden packaging from Asia.
It kills almost everything it attacks: more than 95% of infested American ash trees die within two to five years. Asian trees, which coevolved with it, withstand it.
In February 2025 it was present in 37 US states and six Canadian provinces.
The adult flies little, less than a kilometre, so its rapid spread is explained above all by the human transport of firewood and nursery stock. Hence the campaigns against moving firewood between regions.
It leaves a D-shaped exit hole, an unmistakable trace on the bark.
In 2003 an invasion was simultaneously detected in Moscow, and both appear to stem from a single source in the late 1980s.