Researchers at the University of Georgia have successfully cryogenically frozen germplasm from hemlock trees being wiped out around the country by the Hemlock Woolly Adelgid. This may be the first step in eliminating these invasive tree pests. Their method includes a new way of cloning the few trees they have found that are actually fighting off the pests. The researchers from UGA’s Warnell School of Forestry and Natural Resources published a paper in Trees-Structure and Function outlining their process for generating hemlock tissue cultures, storing them cryogenically just to later thaw them and grow seedlings from the cultures.
While developing their methodology for successfully freezing the hemlock germplasm, they were also able to create a way to clone the hemlocks. This is critically important as they seek to propagate trees with natural resistance to pests and disease. The only 2 native hemlocks have both already incurred major losses due to HWA and their future is bleak if a large-scale solution isn’t found soon. The loss of hemlocks endangers the ecosystems of which they are a part, and would be felt as a domino effect. These trees provide vital services such as erosion control, water quality improvement, habitat and forage for wildlife and carbon absorption.
Warnell professor Scott Merkle, who is also associate dean of research, was lead author on the paper and worked with other Warnell researchers Paul Montello, Hannah Reece and Lisheng Kong. Merkle explains how hemlock populations have exploded since the accidental introduction of HWA in the 1950s, “It looks like a bomb went off where there were once pure hemlocks. It’s just dead trees because there doesn’t seem to be much natural resistance.”
A 2009 study found that unchecked, the hemlock woolly adelgid could kill most of the hemlock trees in the Appalachians within a few years. However, the insects mechanism for mortality isn’t exactly identified even now, although there are solid theories. Many researchers are looking for a way to fight the invasive insect invasion, and chemical controls are effective but may not work in a large-scale forest setting. Work on biocontrol agents and natural predators proceeds while Merkle and his team continue to investigate ways to introduce natural resistance to newly planted hemlocks. Their work on cryogenically storing tissue is critical in the case that none of these methods work before hemlocks are entirely wiped out.