Pests, Diseases, & Invasive Animals

Browntail moth caterpillar crawling on the leaf of a flowering black chokeberry
A browntail moth (Euproctis chrysorrhoea) caterpillar crawls on a black chokeberry (Aronia melanocarpa) leaf at Acadia National Park. The two orange dots, parallel white stripes, and toxic hairs help identify this invasive insect pest.

NPS photo by Jesse Wheeler

Insects alter forest ecosystems in major ways including defoliating and depriving trees of nutrients, which in turn affects all other organisms reliant on that forest type, or community. Some of these pests and diseases have existed in the area before humans. These are called 'endemic' or 'native.'

Others are often introduced accidentally. These are known as 'non-native' and if these non-native insects begin to ferociously out-compete native insects they are known as 'invasive.' Some invasive insects have a history at Acadia, like spongy moth (Lymantria dispar, formerly gypsy moth), Beech bark disease (Nectria coccinea), and balsam wooly adelgid (Adelges piceae) that have been around for decades and become well established.

However, park staff are actively researching and managing a few high priority invasive animals, pests and diseases which threaten key park animals, plants, and ecosystsems. You can help by not bringing outside firewood into the park and washing any boats or watercraft prior to coming to Acadia.

HWA Jordan Stream
Wool from the hemlock woolly adelgid is visible from late fall to early summer.

NPS Photo

Forest Pests

Hemlock Woolly Adelgid

The hemlock woolly adelgid (Adelges tsugae) is an aphid-like invasive insect that was first found in Acadia National Park in 2022. This pest of Eastern hemlock (Tsuga canadensis) has caused widespread damage to forest ecosystems throughout the eastern United States and Canada. Acadia's species profile on hemlock woolly adelgid provides identification and contact information for visitors to report sightings.

Emerald Ash Borer

The emerald ash borer (Agrilus planipennis Fairemaire) is a shiny, green beetle originating from Asia. EAB feed on the phloem (vasculature layer) of all species of ash tree. Once the phloem is damaged, the trees can no longer move water and other nutrients throughout their trunks, and they eventually die, usually within 3-5 years. irreplaceable cultural loss to many indigenous communities. The brown ash in particular is referred to as Basket Tree by Wabanaki Tribes, due to its unique bark structure that allows for the creation of sturdy and beautiful woven works of art. Attached to this practice is also a very spiritual connection to the ash tree.

Though EAB has been detetcted in nearby counties, it has yet to be detected in Acadia. Park staff are actively monitoring for any signs of EAB in Acadia. If discovered, it could have a devestating affect on Acadia's forests.

Red Pine Scale

Park staff and nearby residents have observed red pine declining in health in and around Acadia for more than a decade, but we only discovered the cause in 2014.The invasive red pine scale (Matsucoccus matsumurae), also known as Japanese pine bast scale, was detected near Norumbega Mountain in the town of Mount Desert and Acadia National Park in September, 2014 . This was the first known occurrence in the State of Maine.

The red pine scale insect is native to Japan but arrived in the United States in 1946. The scale insect is about the size of a pin-head and covers itself with a protected white woolly substance that is visible on branches.NPS managers at Acadia are removing dead pines that pose a hazard along roads, trails and parking lots. Ecologists recommend keeping standing dead pines that are not hazards to allow them to break down naturally. They provide good wildlife habitat and return nutrients to forestbsoils. While red pine trees is not the dominent conifer tree in Acadia National Park, the large swaths of dead red pine trees have changed Acadia's forests forever.
Brown Bat with a fluffy white substance on its nose
A Brown Bat with White Nose Syndrome.

NPS Photo


White Nose Syndrome in Bats

Bats are an important part of ecosystems and food webs. Though some species of bats feed on fruit, seeds, or pollen, all of the species that live in Acadia are insectivores. They consume huge numbers of insects every night, filling a unique ecosystem role as nocturnal insect predators. Unfortunately, a new disease called white-nose syndrome is affecting Acadia's bats. White-nose syndrom is caused by a fungus called Pseudogymnoascus destructans. Researchers have learned WNS is spread from bat to bat when they touch and also from cave surfaces to bats. Scientists also think that humans have the potential to carry the fungus from cave to cave, increasing the rate of spread.

Invasive Animals

Asian Shore Crab

On Sept 19, 2019 a student on a Marine Investigations program Schoodic Education Adventure program (SEA) discovered the molted shell of an Asian shore crab (Hemigrapsus sanguineus), an invasive species from East Asia spreading into North America and Europe. This was believed to be among the first confirmed reports of the opportunistic omnivore within Acadia National Park. The Asian shore crab joins the the European green crab (Carcinus maenas), considered one of the world’s worst invasive species, as non-native and invasive crab species creeping into Acadia's waters.

Learn More About Pests, Diseases, & Invasive Animals at Acadia

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    Last updated: February 2, 2023

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