Part 6: The Race AgainstTime Versus Scientific Data
Story by Sam Calhoun
After reading Part IV of this series on the hemlock wooly adelgid (HWA)—Dr. Richard McDonald’s explanation that bracketing the HWA with three species of beetles will achieve the balance that can save the High Country’s forests from the HWA—Dr. Fred P. Hain, professor and director of graduate programs in the Department of Entomology at North Carolina State University, emailed a message stating his concern that no scientific studies to date have demonstrated an impact by the predators when released in the East.
While agreeing that the work with predators should continue, Hain said that before spending large sums of money for mass rearing and releasing predators, the players involved in fighting the HWA need some assurances that the predators will work.
“Pesticide companies are not allowed to market new insecticides until they have accumulated sufficient data to demonstrate the efficacy of the compound,” Hain wrote. “The same criteria should apply to biological control. My fear is that an overzealous emphasis on predator releases will divert funds from other areas of research that are critical in understanding and managing the hemlock woolly adelgid problem.”
But is there enough time to conduct scientific studies on natural predators while the HWA continues to kill the hemlocks?
“I think the public right now gets the impression that, when they read statements like McDonald made, predators are the answer, and I hope he’s right,” said Hain. “But at the moment, I think it’s overselling what might be a promising approach, but we’re not there yet. It may be doing more harm than good.”
Hain pointed out that the Sasajiscymnus tsugae beetle that McDonald explained was part of the bracketing process “looked promising because it was specific to the adelgid, fed on all life stages of the adelgid and had two life cycles per year. Unfortunately, there’s not been a lot of success with it.”
The Laricobius nigrinus predatory beetle, also part of the bracketing process, “seemed to be a bit more promising,” said Hain, but its impact has yet to be seen because it has only been released in the last few years.
Hain would rather have seen small-batch releases observed over many years with corresponding data collection. In his opinion, the Sasajiscymnus tsugae beetle was released too fast in too great a number.
Possible Solutions: NC State Initiatives
Because Hain feels that more data needs to be collected on the use of predators to fight the HWA before mass rearing takes place, he tells concerned residents that if they must save their trees now, chemical methods are the best solution. High value and big trees can be saved through chemicals, but not on a large scale.
“Biological controls are the long-term solution, but if you want to save individual trees, you’ve got to go with pesticides right now,” said Hain.
Hain pointed out that the HWA could easily have been controlled in the 1950s when it first made its presence known on the East Coast in Richmond, Va. But that didn’t happen and the HWA migrated to natural stands. Now it is economically infeasible to treat large infestations with pesticides.
NC State has begun two research initiatives with the aim of developing a straightforward, proven method of control that is backed up by scientific research.
The first initiative is the Hemlock Forest Partnership. This initiative is built on the theory that predators will only work if the tree has some natural resistance to the HWA. Scientists participating in the partnership will look for resistance in the Eastern and Carolina Hemlocks. If they do not find any resistance, they will experiment with hybridizing the Eastern and Carolina Hemlocks with species that have proven to be resistant, such as the Asian or Western Hemlocks.
The second initiative is to create a game plan for the future, so if the hemlock populations are wiped out before the long-term predator studies are completed, there will be a chance for restoration once a proven method is devised. Researchers at NC State have been collecting hemlock seeds, putting some of them in storage and planting some of them in other locations, such as Brazil and Chile, that are outside the natural range of the HWA.
“So if we do come up with a solution, we’ll have a chance to do a restoration project,” said Hain. “In the next ten to twenty years, we will know the answer.”
For the present, Hain hopes that players in the fight against the HWA won’t release too many predators before sufficient data is collected on the long-term effects.
“It may leave biological control with a black eye—that biological control can’t work,” he explained.
Hain hopes for a coordinated partnership in which one agency is in charge of the fight on the federal level. Such a coordinated partnership, Hain said, could provide an improved infrastructure that will increase communication and information, as well as funding.
“The way the system is working now, there needs to be a comprehensive research and application effort,” said Hain. “Right now, it’s more of a piecemeal approach.”
EXTRAS: Other Things To Consider
If you have comments or experiences that you think will help with this community education project, send them via email to sam@highcountrynews.info.
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