Killer of White Oaks in Ozarks Still at Large
MU scientists have narrowed down the possibilities of what might be causing white oak mortality in low-lying areas of Missouri Ozarks in the past few years. But the mystery remains.
Dr. Sharon Reed is trying to solve the mystery. She's an MU research scientist who has been working on the white oak mortality issue for some time. She said some of her research is very low-tech like scraping bark off of dead white oak trees. "Part of the process with the scraping is that we actually do try to isolate pathogens in the wood tissues. And we do that by taking out little chips from the areas that are darker in coloration."
Those little chips she's talking about are fungi that end up on a Petri dish to grow and eventually be analyzed. "We are looking for things that are consistently associated with these trees that are declining or dead," Reed said.
Like Fungi taken from an ambrosia beetle. "It's a wood-boring beetle that has consistently emerged out of dying and dead trees at our study locations that have rapidly dying white oaks," Reed said. But that doesn't mean the ambrosia beetle or the fungi it's carrying is causing white oak mortality. It's much more complex than that. Reed said it's very likely the beetles and fungi they're finding do kill tissue in the white oak but only in trees that are already weak. Weak from pathogens that live in the soil and kill roots.
In the past few years the scientists have been digging up roots and taking soil samples near dead or dying white oak trees on federal forest land in Maries and Osage counties. "We found a fungus-like organism called phytophthora cinnamomi. Some people call it a water mold," Reed said. "Finding this organism is important because it has been found to be associated with oak declines globally."
Reed said the fungus prevents the tree from absorbing water and nutrients and is very good at protecting itself. And she said that's not all. "Could be there are multiple pathogens working on these trees."
MU biologist Rose-Marie Muzika leads the team of scientists doing this research. "What we have found with most of these trees is that they have barely been growing for as much as 20 years," Muzika said. "So although we are seeing this death happen now, we could suspect that 20 years ago, or 15 years ago, in the life of the forest and of this tree, something else went on."
Muzika also pointed out that because of the complexity of white oak mortality, it might take 5-10 years of further study before they can get a good handle on what's killing the white oaks. That's a long time but she said this is serious stuff and they don't want to make any hasty decisions before advising forest managers how to better deal with white oak mortality in forests that might be there for hundreds of years.