HWA in Cook Forest – 2020 Update

Hemlock Woolly Adelgid¬†– it’s a non-native invasive insect that’s a massive threat to the old-growth hemlock trees of Cook Forest, and it’s still here.

Hemlock Woolly Adelgid in Cook Forest State Park - present in 2020

Hemlock Woolly Adelgid in Cook Forest State Park

Hemlock woolly adelgid (HWA) has been consistently treated by state agencies since it was first found in Cook Forest State Park in 2013.  First – the bad news – it’s still here.  The photo above was taken in May 2020, and those white little cotton-like tufts confirm the presence of HWA on hemlock trees within park boundaries. 

The good news: 

  • the infestation is not blanket, but concentrated in small areas; 
  • the Eastern Hemlocks in Cook Forest remain largely healthy;
  • the state is continuing treatment, even in this most uncertain of years — 100,000 inches of trees are scheduled to be treated again in 2020, as soon as rainfall rises the water to levels enabling soil injection

HWA was never going to be a short-lived threat, and it’s important to keep in mind the utter devastation it wrought in the Great Smoky Mountains, where it hit first, and in a warmer climate.  The PA Bureau of Forestry continues to work toward establishing a bio-control for the insect, as exists in places where HWA is native (the Pacific Northwest and Japan).  Until then, regular treatments can keep these hemlocks healthy, and their surrounding ecosystems intact.  Eastern Hemlock is a “keystone” species, and integral for keeping our streams cool and clear, for filtering pollutants, and for and managing storm runoff. 

These tasks become more challenging as our climate cycle changes – we’ve experienced stronger, shorter storms punctuating long dry periods, which means less water is being absorbed into the aquifer.  Western Pennsylvania also had a warm winter, which favors reproduction of HWA – and they reproduce exponentially.

HWA – What can be done by individuals to protect Hemlock trees?

Monitoring is of utmost importance – regularly check the health of the hemlocks in your yard, and stay vigilant when hiking or out on state forest lands.  Since HWA often infects trees from the top down, especially check branches blown off by wind, and the upper canopies of hemlock trees that have recently fallen.

We appreciate your supporting ongoing efforts – both in the state and private sectors – to control HWA.

  • Private landowners seeking assistance for trees they think may be infested can contact the CFC, or their county’s Service Forester.
  • To report infestations found on public land, please email PaForester@pa.gov – it’s ideal if you can provide a GPS location, and a clear photograph of the suspected bugs, as well.

Follow these links to learn more about the importance of eastern hemlock, or the invasive insect threatening it – hemlock woolly adelgid.