There’s nothing quite like picking fresh fruit from trees and biting into it–savoring its sweetness. What’s not so sweet? Spotting a fuzzy fungus as you reach for your tasty treat.
Not only does a fruit tree fungus spoil an appetite, but it also sparks all kinds of questions about tree health.
Cyndy W. from California asked, “It looks like my plum tree has a fungus growing on it, and I don't know how to treat it or if it will spread and I'll have to take the tree down. It is a white and hard growth in two different locations.”
Find out which fruit trees get infected with this fungus and learn whether treatment or tree removal is the best option.
Above, Cyndy’s tree appeared to have a white fungus, but don’t ignore your tree if that’s not exactly what you see. Black knot disease can look different, depending on the stage it's in.
It’s likely black knot, which is a fungal disease that most frequently attacks plum and cherry trees. In spring, a velvet-like green appears on branches. It gradually grows and becomes hard and black by fall, which is usually when you’ll spot it.
The following year, the fungus starts to expand. The chunky, black growth gets larger, wraps around branches and may invade the tree’s trunk.
In some cases, older black knots will turn white or pink, like on Cyndy’s tree. But, typically, you’ll see a solid (albeit lumpy) black growth.
Primarily, this fungus goes after plum and cherry trees, especially American plum, purple-leafed plum and chokecherry. It can affect other fruit trees, like apricot and peach, but it’s not as common.
Because the disease only affects the tree’s wood, it’s A-OK to eat fruit from trees with black knot. But as always, check that the fruit is fresh before digging in.
The best way to get rid of black knot disease is to have your arborist prune out the affected branches. Specifically, here’s how they’ll approach the treatment of black knot on your trees.
Joseph O'Brien, USDA Forest Service, Bugwood.org