For years, Adam Downing, a forestry and natural resources agent with Virginia Cooperative Extension, has passed a big, healthy white oak tree on his drive to work.
This summer, he noticed as two-thirds of the tree’s foliage turned brown in just a few days, and the tree looked like it was dying. Within a month, the tree had been removed.
“I can’t say I’ve ever seen an otherwise healthy-seeming tree brown out like that,” said Downing. “My experience is consistent with other calls we’ve gotten from around Virginia this year. It’s almost always a white oak and people report that it suddenly looks dead.”
Is some mysterious new disease or pest killing old, otherwise healthy-seeming oak trees?
Probably not.
According to Downing, while a combination of factors contributes to oak decline, our unusually wet weather through last summer into the spring likely stressed many Virginia oaks and may have caused this year’s increase in oak mortality.
“Last year’s wet weather is the only thing that seems different,” said Lori Chamberlin, a forest health program manager with the Virginia Department of Forestry. “Oak decline is happening in the background for a lot of trees, and it’s likely been accelerated by the extreme weather we’ve had.”
Predisposing factors, such as poor soil or old tree age, reduce an oak tree’s ability to fight off pests and make it more susceptible to inciting factors, such as frost or defoliating insects that may initiate oak tree decline, according to Chamberlin. An oak tree may be in decline for years or even decades, and contributing factors like secondary insect pests or diseases that ultimately lead to tree death are just the last nail in the coffin.
The biggest routine stress most urban trees face is the urban environment, according to Downing. Urban trees deal with factors like competition from turfgrass, compaction of soil by foot traffic and vehicles, and even urban heat islands.
Homeowners concerned about their oak trees can promote tree health by practicing basic maintenance, including reducing or preventing compaction of soil around the tree, watering during periods of dry weather, and providing proper mulching. Good practices like these can help extend the life of a tree, even if it’s already in a gradual decline.
Downing recommends that property owners keep vigilant by taking a monthly walk around to look for problems.
“For a lot of tree-health things, if you catch it early, you can help the tree,” he added.
Tree owners also need to remember that oaks have a finite lifespan.
“If your oak tree did die this year, don’t be afraid to plant another oak tree!” said Downing. “Don’t be afraid of oaks because they’re slow growing. They have so much value in the food chain and they’re great trees.”
If the small size of a newly-planted oak tree deters you, think of it as planting an “oak bush” instead, Downing added.
To learn about planting trees in parking lots or areas with pavement, see this Extension publication.
To learn about planting trees in hot sites such as next to buildings, see this Extension publication.
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