1.5 mm in size. Can be identified by the fuzzy white spots they create on hemlock trees.


The hemlock woolly adelgids use their sharp mouthparts to pierce hemlocks at the base of a needle. They feed on the starches in the tree and slowly starve the tree of nutrients.


A species of beetle, Laricobius nigrinus, and silver flies are being tested as biocontrols.

Reproduction and Life Cycle

There are generally two broods each year. An overwintering population will mate in the spring and produce new nymphs which will mature and mate in late summer producing the population that will overwinter the following year. The nymph stage is when they are most likely to move and be introduced to a new location.

All of the woolly adelgids in eastern North America are female, but they are capable of reproducing asexually. Each year a female can lay 200 eggs and within the same year those eggs reach sexual maturity and each adult can lay another 200 eggs.

Did You Know?

  • Keeping bird feeders away from hemlock trees can help stop the spread of this invasive insect. Migrating birds visiting feeders can carry the tiny adelgids and help them spread.
  • As climate change has increased winter temperatures, the woolly adelgid’s range has expanded farther north.
  • An adelgid infestation can kill a full-grown hemlock tree in less than four years.

Sources and Additional Information