KANE — While most people do not pay much attention to the Hemlock Wooly Adelgid, or likely even know what it is, its presence has a direct impact on both the local ecology and economy. It was also the main topic of discussion at the Roach Bauer Forestry Fall Forum on Thursday evening at the Kane Country Club.
The panel of experts who presented on Thursday on the Hemlock Wooly Adelgid, all of whom work for the U.S. Department of Agriculture, Forest Service, were Mary Ann Fajvan, research forester with the Northern Research Station based out of Morgantown, W.Va.; Talbot Trotter, research ecologist with the Northern Research Station in Hamden, Conn.; and Bud Mayfield, research entomologist with the Southern Research Station in Asheville, N.C.
Fajvan spoke of controlling the pest from a silvicultural angle. She said the Eastern Hemlock, the species of the conifer indigenous to the Allegheny National Forest, is the most shade tolerant conifer in the eastern forest.
Fajvan said the value of the hemlock timber itself is not extremely high, but the role it plays in the forest ecosystem itself is at risk. She said hemlock forests are habitats for such animals as the ruffed grouse, black bear and whitetail deer. Fajvan noted the benefits hemlocks have in the watershed hydrology.
She gave three options to combat the adelgid from a silvicultural viewpoint: Thin targeting hemlock crop trees, cut the shelterwood and let it regenerate, or absolutely nothing.
Thinning the stands of hemlocks may not only help fight the adelgid but also increase revenue from timber, she said. She noted the increase of the diameters of the timber left standing after the thinning, with an increased diameter of 1.1 to 1.6 inches in three different stands over the course of six years.
Fajvan said if a shelterwood cut is selected, 20 to 50 percent of the basal area of the stand must be removed, including the dying and damaged hemlock.
By doing nothing and letting infested hemlocks die, Fajvan said, the light to the forest floor would increase, thus allowing other seedlings to thrive. She said the entire forest could turn into a hardwood forest.
While the species in Asia and the Pacific Northwest are native species, the adelgid common in Pennsylvania originally came from an area outside of Osaka, Japan, according to Trotter. He said while the first instance of the adelgid was recorded in Richmond, Va., in 1951, the adelgid likely first came stateside in the early 1900s, when Asian gardens were popular and imported hemlock trees from Osaka were not uncommon.
Trotter said the adelgids can freeze to death, unlike many insects which merely wind up in stasis. He said as the temperatures get lower, less of the pest will survive.
Trotter also spoke of the “two percent rule,” which states that if the more than two percent of the adelgid population survives over the winter, the adelgids will continue to thrive. However, he said if that number drops under two percent, the population of adelgids will start to dwindle.
Mayfield would like to see a combination of insecticides and biological controls be used together in controlling the adelgid. He said neo-nicotinoids such as Imidacloprid and Dinotefuran are very effective in controlling the adelgid, but they must be applied to each affected tree every seven years, making it somewhat costly.
Mayfield said a natural predator of the adelgid, a beetle called the Laricobius Nigrinus, is also effective in controlling the adelgid naturally. However, he noted the difficulties in having the beetles reproduce quickly enough to be able to keep up with the adelgid.
Mayfield said a possible strategy would be treat some of the infected trees with the insecticides, release the beetles on the untreated trees, and let the insecticide slow the adelgid growth while the beetles numbers increase over time.
Ned Karger, chairman of the steering committee for the forum, said 118 people registered for the 2015 Fall Forum, which is the second highest attendance total in the 31 years, matching the figure from the 25th anniversary forum in 2009.
Karger presented Fajvan, Trotter and Mayfield with the traditional Black Cherry biltmore sticks, given to those who speak at the forum.
The next forum will be held on April 7, 2016, with speaker Bob Long discussing his research on the decline of black cherry in the area.