Verticillium wilt - Ask Extension
We cut down a a 18’ tall swamp oak due to a horrible infestation of gall wasps (which attacked hornets and flies).. it was growing steady around 2â€...
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Verticillium wilt #870032
Asked May 25, 2024, 8:52 AM EDT
We cut down a a 18’ tall swamp oak due to a horrible infestation of gall wasps (which attacked hornets and flies).. it was growing steady around 2’ a year. When we cut it down we noticed the core was very dark almost black. (Photo attached). Could this be verticillium wilt? Even though the tree didn’t show other signs? We have a thriving smoke bush that also has a black center when it gets trimmed and we are stumped as to why? We don’t want to plant something in its place if it’s going to become infected.
Baltimore County Maryland
Expert Response
If the tree was asymptomatic for Verticillium Wilt, that fungus was not likely present. Many tree species have normally dark-colored heartwood once they get old enough. Knowing the exact ID of the tree might help to confirm a normal heartwood color, since "swamp oak" might refer to at least two different species that are not closely related: Swamp White Oak (Quercus bicolor) and Pin Oak (Quercus palustris; the other common name is Swamp Oak because palustris means marsh-loving). We can't say why the Smokebush has dark wood either, but if the plant is not symptomatic and has had those characteristics for a while, it's not a problem since the shrub/tree would likely be in visible decline by now in that case.
Many plant pathogens, including wilt and root rot diseases, are fairly ubiquitous in the environment. It's generally only when the host plant becomes vulnerable to infection, such as from drought or over-watering stress, over-fertilization, or injury from excessive pruning or storm damage, that the likelihood of infection becomes a risk. Even then, decline and death are not guaranteed because trees/shrubs do have ways of internally compartmentalizing wood decay and damage from spreading to the rest of the plant; it's not foolproof, but it can suppress some conditions from worsening. One key to keeping the risk of wilt disease infection low is to avoid wounding the plant, such as from a very common source of injury, mowers or weed-whackers trimming turf around the base of the plant's trunk or main stems. (A mulched zone around the plant's base helps to avoid this.)
Miri
Many plant pathogens, including wilt and root rot diseases, are fairly ubiquitous in the environment. It's generally only when the host plant becomes vulnerable to infection, such as from drought or over-watering stress, over-fertilization, or injury from excessive pruning or storm damage, that the likelihood of infection becomes a risk. Even then, decline and death are not guaranteed because trees/shrubs do have ways of internally compartmentalizing wood decay and damage from spreading to the rest of the plant; it's not foolproof, but it can suppress some conditions from worsening. One key to keeping the risk of wilt disease infection low is to avoid wounding the plant, such as from a very common source of injury, mowers or weed-whackers trimming turf around the base of the plant's trunk or main stems. (A mulched zone around the plant's base helps to avoid this.)
Miri
Awesome, thank you. It was a Swamp White Oak. We would like to replace the tree and just wanted to make sure we wouldn't be placing a tree in the area where the bacteria for verticillium wilt was present. But, the tree showed no other signs, nor the smoke bush which seems to grow 4'-6' per year even after we trim it back in the winter.
You're welcome. (Verticillium Wilt is caused by a fungus, incidentally, not a bacteria.) And yes, Smokebush, despite "bush" in its name (it's also sometimes called Smoketree), matures quite large unless it's one of the fairly new dwarf cultivars, so a size of around 10-15 feet is not uncommon. Fortunately, they tolerate drastic pruning fairly well.
Miri
Miri
