From time to time we bring you stories about insecticide spraying in Great Smoky Mountains National Park to combat a non-native pest that is a threat to the park's stands of Eastern hemlock trees.

Another chapter of that saga comes from Friends of the Smokies, which raises funds to help carry that battle to the pests.

The focus of all this work is the hemlock woolly adelgid, an Asian pest that arrived in the western United States in 1924 and was first identified in the eastern section of the country in 1951. According to the Pennsylvania Department of Conservation and Natural Resources, "Hemlock woolly adelgid sucks fluid from the base of hemlock needles. It may also inject toxins into the tree as it feeds, accelerating needle drop and branch dieback. Although some trees die within four years, trees often persist in a weakened state for many years. Hemlocks that have been affected by hemlock woolly adelgid often have a grayish-green appearance (hemlocks naturally have a shiny, dark green color)."

Now, it's been nearly a decade since these pests reached the Smokies, according to the friends group. Fortunately, the non-profit's efforts have seen considerable success in battling the insect in the park. Donated funds help hire crews and equipment to do the insecticide spraying in the park, and they also have helped create "the Lindsay Young Beneficial Insects Laboratory at the University of Tennessee-Knoxville to raise predator beetles to release in the park and elsewhere to kill the adelgids."

To date, the park's hemlock crews have hand-treated more than 140,000 trees in nearly 4,000 acres of special hemlock conservation areas. They have treated another 600 acres along roads, campgrounds, and picnic areas with a naturally-based insecticidal soap. Since 2002, the insect lab has provided more than 500,000 predator beetles to release in the park.

... Thankfully, we have more encouraging results to share from the Smokies. Treatments originally expected to last only 2-3 years are showing positive results for as long as 5-10 years. Treatment costs have come down. A new, naturally-based insecticide, dinotefuran, is showing even better effects for the park's tallest hemlocks. Park researchers have recovered live beetles from releases as far back as 2002, providing promise that they will sustain themselves in the wild for the long term. Also, some small (10-30 acre), higher-elevation stands are surviving untreated, because of colder winter temperature fluctuations and rime ice.

To continue this battle, however, takes money. And the friends group notes that it could take many more years to find the right approach to rid the park's forests of the threats posed by the hemlock woolly adelgid.

This year the group hopes to be able to give the park another $50,000 to continue this effort. You can help them reach that goal by contributing through a donation to the Friends of the Smokies at this site.