NCSU scientists enlist public's help in protecting Christmas trees

Wooly adelgid and infestation.

Adapted from NC State Magazine, Spring 2013, author Angela Spivey. 2013 Annual Report with research study outcomes to follow.

The dark greens of Christmas trees fleck with lights have long been a symbol of the holiday season. But we don’t see what could have been living on those trees when they were in the wild—wooly adeglids (pronounced “uh-del-jids”). These tiny insects threaten Fraser firs, the most popular Christmas tree in the United States, and hemlocks, which prevent erosion and serve as a source of lumber.

Though the insects are too small to be seen, they leave tell-tale white, wooly masses on the trunks or branches of a Fraser fir or on the needles of hemlocks. The wooly masses are the sacs that protect the insects’ eggs. During the spring of 2013, scientists at NC State University asked the public to report when they saw signs of infestation on trees in the wilderness and to send pictures and notes about the trees to scientists behind the Tiny Terrors Project, led by NC State entomology professor emeritus Fred Hain. “Tiny Terrors is an effort to add more eyes in the woods,” he said.

The Tiny Terrors Project was put together by the Alliance for Saving Threatened Forests, a group of scientists up and down the East Coast who banded together to fight adelgids, restore the population of Fraser firs and hemlocks, and breed resistant trees for the Christmas tree and ornamentals industry. Hain co-founded and leads this group of scientists.

“The ideal solution is to find trees in nature that already have reesistance and then propagate those trees,” Hain said. An alternative would be to find a gene that confers resistance to adelglids and then genetically engineer trees to contain that gene. If scientists can find trees in North Carolina that are infected but not dying, they’ll take cuttings from them, root them, then test the offspring to find out if it is indeed resistant to adelgids.

Hemlock wooly adelgids have devastated the NC hemlock population. The pests don’t kill young Fraser firs, but affect their quality as Christmas trees because the wood of young infested trees hardens and loses its ability to transport water to the foliage. The trees may drop needles more easily and lose their “atypical dominance”—the tree's top tip where the Christmas star or angel is perched. The pest can also kill older trees that serve as seed stock for Christmas growers, and controlling it requires expense hand spraying of pesticides.

The adelglid originated in Japan, but the pest was transported to the US from Europe in the early 20th century, most likely on nursery stock, according to the US Department of Agriculture. North American trees had not yet evolved to live with the pest so the effect was devastating.

2013 Annual Report (full report-http://www.threatenedforests.org/Annual%20Report.php)


Artificial infestation of Fraser firs in the lab.

"Screening for adelgid resistance in Fraser fir began in spring 2012, with 30 genotypes from the NC Premium Fraser Fir Seed Cooperative and 6 genotypes of survivors previously collected from natural stands in Great Smoky Mountains National Park. Genotypes were grafted onto Fraser fir rootstock in spring 2012, and artificial infestation initiated in May 2013. However, during the infestation process (indoors), the trees began exhibiting signs of stress. Electrical conductivity tests suggested a buildup of salts had resulted in fertilizer burn. Efforts were immediately undertaken to flush the accumulated salts to remedy the problem, but we were unsuccessful, and the entire test was lost. We will repeat the screening test in spring 2014, which is the earliest the genotypes can be grafted again.

…In our BWA screening trial in 2013, we had difficulty locating a sufficient number of trees in suitable state of infestation, prompting us to explore ways to ensure a reliable supply of adelgids in the future for fir and hemlock screening. As a result, we plan to start maintaining a population of hemlock wooly adelgid at the Mountain Research Station using the large seedlings surplus to our immediate needs, as well as any trees we can obtain from growers unable to market stock they would otherwise be forced to discard. We are also trying to develop methods to successfully rear adelgids in a lab, ensuring a uniform, reliable supply for testing. Economic difficulties in both the Christmas tree and ornamental nursery industries have led to unpredictable commercial supplies of the trees we need, so we are planning to propagate trees internally to supply our future anticipated needs, reducing our reliance on outside growers.”