How to Combat Blight on Trees

Brown spots on a tree leaf

Blight is a quick and deadly tree disease that can potentially affect almost any tree in the U.S., which makes it a huge problem. Knowing how to combat blight is essential. If you don’t treat this problem as soon as it strikes, it can kill not just one tree but entire tree populations. There are several types of tree blight, but the treatment is generally the same for all these different diseases.

Fire Blight

Fire blight causes discoloration, usually on the bark of trees, though it can also affect blossoms and roots. There is no cure for fire blight. Once it affects your trees, your only hope is to completely eliminate the blight by pruning it off the tree. To successfully remove fire blight, you actually have to over-prune. You need to cut 12 to 18 inches above and below the areas of the tree that are visibly affected.

Diplodia and Dothistroma Blight

Almost all species of pine can potentially be infected with diplodia and dothistroma blight. Diplodia blight makes needles of pine trees turn brown. This blight also stunts growth in new shoots, which can ultimately make the tree look malformed. Dothistroma blight kills needles on evergreen trees. Over time, dothistroma blight can kill a tree if it's not treated.

At first signs of either one of these types of blight, the infected tree should be pruned. Cut away all infected areas of the tree, and cut several inches above these areas to prevent the blight from spreading and ensure it has been fully removed. Once all the pruning is complete, use a fungicide to kill the blight and prevent future outbreaks.

Pine trees drying out

Chestnut Blight

Don't let the name of this tree blight mislead you. Hardwood trees of all kinds, not just chestnut trees, can be infected with chestnut blight. This blight is incredibly deadly and capable of killing entire populations of hardwood trees. There is no cure for chestnut blight, so prune diligently when it pops up.

Dutch Elm

A type of blight specific to elm trees, this fungal infection can be spread by beetles. As a precaution, you can inject your elm trees every two to three years with a protective treatment, which will at least reduce their chance of contracting the disease.

Verticillium Wilt

One of the most pernicious and dangerous kinds of blight, this wilt affects many kinds of plants, from hemp to vegetables to maple trees. The tricky part to addressing Verticillium wilt is that it lives in the soil, so pruning dead branches stems with browning leaves might not be enough. In extreme cases, you might have to remove your tree, though you can try fumigating your soil with chloropicrin first.

General Tips for Treating Blight

When pruning away potentially infected branches and other parts of trees, dip your pruning shears in bleach before you make each cut. This will help prevent the blight from spreading to healthy parts of the tree. Once all the infected areas of the tree are cut away, treat the tree with fungicide to prevent the blight from spreading and infecting new parts of the tree. This method is effective for all types of tree blight.

Tree Diseases

There are many other types of tree diseases and problematic bacteria that can potentially kill trees, stunt their growth, or ruin their foliage. If your initial treatment does not work, you may have a different type of tree disease that isn’t blight at all. When in doubt, call in a professional gardener or tree specialist to find out how to stop your tree disease.

Spraying fungicide on a cherry tree

Combat Blight on Your Trees

As soon as you think you have a blight problem, start combating it. If you don’t act quickly and decisively to treat blight, it’s not just your trees that can potentially be affected. Blight can spread to every tree in your neighborhood, changing the landscape for generations. This is a dangerous problem, but you can fight it with pruning, fungicide, and a little bit of time and care.