With several hot, dry summers in the rear-view mirror, landowners might want to be on guard of hypoxylon canker, a tree disease that affects hardwoods, especially the red oak group.

“Hypoxylon canker is a fungus, it normally decays trees after they are already dead,” said Nate Forbes, forestry district supervisor, Missouri Department of Conservation, Neosho. “What we’ve noticed – the summers of 2011 and 2012 were so dry and droughty that a lot of our timber lost the available moisture content that it needed, and in some places stressed trees started getting this hypoxylon canker when they were alive.

“Most of what we’ve seen are black oaks and red oaks being affected by this, but in a few places – on higher, drier landscapes – we’ve even seen white oak and post oak affected by this canker.”

Forbes said hypoxylon is a common canker, but the overall health of the forests is the greatest concern, as well as trees in yards and communities.

“The long-term thought process here is that if we get into drought conditions, if somebody has a good, large, mature tree in their yard, they may have to consider some supplemental watering to keep that tree healthy,” he said.

“Cumulative stress is what has allowed this fungus to take advantage of some of our trees, so, whether it’s a lack of forest management out in the woods – thinning poorer trees and using them for forest product or for firewood – that’s one way to keep the forest healthy, and then in a yard setting, watering our trees during drought, hiring certified professionals to do tree care on that tree, making sure to not compact the roots or damage the trunk with our mowers or string trimmers, things like that can keep our trees healthy.”

Symptoms of hypoxylon canker include a gray patch that Forbes said sometimes evolves into a black patch on the side of the tree.

“Normally the tree will be in pretty rough shape, the crown of the tree will be dying by the time you see this canker on the side of the trunk,” he said. “Typically you will see the tree dying from the top down – it may still have some green foliage further down on the tree – but the top may be dead and then you might start seeing these grey or black patches on the side of the tree.”

As the disease advances, he said large areas of bark fall off the branches and the trunk, revealing a thick, dusty fungal mat with tan spores.

Once symptoms are noticed, Forbes said, “At this point, the tree’s a goner.”
For a yard tree, he said the determination on whether the tree needs to be removed might be if at least 50 percent of the crown is dead.

“Maybe the tree is stressed and it’s lost just a small amount of its crown, at that point maybe some regular watering once or twice a week through droughty periods may help that tree along, but then some pruning may be called for to prune the dead wood out of the tree,” Forbes said.

Forbes recommends that landowners pay attention to how their trees look.

“Sometimes changes in color or loss of vegetation, sometimes there are insects that get on our trees and we need to defoliate them, or sometimes they cause bumps on the leaves, if somebody has a yard tree that they are really caring for, keep an eye on it and keep watching it, and if they do find something they are welcome to send pictures or leaf samples over here to the office and we’ll try to do our best to help them find out what is going on with their tree,” he said.

The MDC Neosho office is located 1510 Business Interstate-49. Call 451-4158.