How to Rid Your Trees of Black Knot Disease

Trees can get sick just like people do. There are a plethora of different diseases and infections trees can develop. Some are like the common cold: seasonal and mild, while others are like a cancer: reoccurring and deadly.

If you’ve taken a look at the plum and cherry trees in our area recently you may have noticed some large, black lumps or “knots” covering various parts of trunks, branches and stems like tumors. Trees with these “knots” are infected with a disease called: Black Knot Disease.

What is Black Knot Disease?

Black Knot Disease is the infestation of a fungus technically* known as Apiosporina morbosa that is common to plum and cherry trees as well as other fruit trees like apricot and peach trees. The fungus takes form in small green or brown swellings that, without treatment, turn into large, black “knots” that drain the life from infected limbs and twigs. Not only can this disease disrupt the growth of your trees, but it can also kill them completely.

Black Knot Disease is a chronic issue. It will continue to spread throughout your tree no matter what the season. The fungus lays dormant in the knots during the winter and spreads its pores during the spring months.

How to Doctor Black Knot

Like humans, trees need check ups to make sure they are healthy. If you or your tree-care professional notices Black Knot on one or more of your trees, it’s time to play doctor and remedy the issue. Here’s how in 3 simple steps:

1. Cut away branches and stems that have any signs of the disease
   If you notice black growths on your plum or cherry trees the first thing you have to do is amputate the infected areas. This may seem like an extreme first step, but unlike humans trees have the ability to regenerate their limbs. Make sure you cut 2 to 4 inches below the growth so you are removing all of the infected wood.
2. Burn or bury the cut-off branches/stems
   It’s important to make sure the infected limbs are properly laid to rest by either burying or cremating. These are the only two ways to insure the fungus cannot spread to other trees in the area.
3. Use an appropriate fungicide
   While your tree is in remission, it’s important to use the proper fungicide to keep your tree Black Knot free in the future. Fungicides vary in their effectiveness depending on what region you’re in so it’s important to check with your tree care professional to find out which fungicide is right for your area. Also note that it’s imperative that you follow the label on your chosen fungicide and re-spray at the appropriate time intervals to keep your tree from relapsing.

If you suspect you have a tree with Block Knot disease, give us a call at (201) 444-0315, so we can work with you to start a treatment plan.

*If you want to check out more technical information on black knot fungus, its cycle, and its biology, you can here.