Top Notch
Tree Service

Your Guide to Common Tree Diseases and How to Identify Them

Close up of Pensacola tree service professional performing tree removal with chainsaw.

Did you know that trees can produce up to 260 pounds of oxygen every year? With such benefits, it’s a no-brainer that we should protect them at all costs.

The secret to ensuring your trees live a long and healthy life, is providing them with adequate nutrients and water. Even then, tree diseases can still negatively impact and harm your tree’s overall appearance and health. Failure to treat or remove diseased trees can be fatal, as tree disease can spread throughout your entire landscape.

To stay on top of your tree maintenance, you need to know the common tree diseases, their symptoms, and how to mitigate them. Be on the lookout for the following diseases:

Root Rot

This prevalent tree disease is caused by a fungal infection. It often affects trees planted in moist or contaminated soil and those with damaged roots or stems. If decomposition from earlier infestations is present in the soil, new plants may develop root rot.

Some of the common root rot symptoms include:

  • Needle failure
  • Browning or mild yellowing of the needles
  • Discolored wood near the stem’s base
  • Poor growth
  • Separation and loosening of dead bark

It’s quite challenging to treat root rot and completely eliminate the fungus from the soil. The best solution is often removal of infected trees and to plant trees far away from poorly drained soils, downspouts, and other water catchment areas.

Rust Fungi

Rust diseases are caused by tree fungus and usually seen in late August. Birches, red cedars, oaks, maples, cottonwoods, and poplars are particularly susceptible to this tree disease. Fruit trees such as pear, quince, crabapple, and hawthorn may also be affected.

Common symptoms of this disease include:

  • Cankers on branches, twigs, and trunks
  • Twig galls
  • Orangish fungal spores on twigs
  • Broken, rotten, or distorted fruits

Rust-infected trees frequently lose their leaves by mid-summer, impacting their growth and agricultural productivity. Remove any obvious galls on trees by April to prevent rust infections. You may also plant susceptible trees far apart to prevent an infection from spreading.

Bacterial Leaf Scorch

Bacterial leaf scorch is a systemic disease caused by the bacterium Xylella fastidiosa. It invades the nutrient- and water-conducting tissues (xylem) of susceptible trees.

This bacterial disease affects red, pin, bur, white, and shingle oaks, but can also affect sycamore, oak, elm, sweetgum, mulberry, sugar maple, and red maple.

The bacterium is mostly spread from tree to tree via xylem-feeding spittlebugs and leafhoppers. There are also reports of transmission through root grafts.

Every mid-to-late summer, infected plants’ leaves may exhibit uneven browning. Browning can spread from lower to upper branches. Some tree species may have a yellowish color or a “scorch” surrounding them.

Although there are no cures for leaf scorch caused by bacteria, dead timber, and diseased branches can be pruned.

Powdery Mildew

Powdery mildew is caused by tree fungus and distinguished by white spots that resemble dust or powder patches. This dust accumulates on diseased trees’ leaves, shoot tips, stems, and flower buds.

Leaves of severely infected trees turn brown and drop. The disease prefers young and succulent trees growing in the shade, but may also affect mature trees. The fungi may infect a plant during the growing season, survive the winters in the leaves, and then spread to younger plants the following spring.

Although powdery mildew is unlikely to harm the whole tree, it can create twisted and stained leaves and blossoms. The condition prevents the plants from obtaining light.

To control this disease, consider planting resistant tree varieties, fungicides, and cultural control practices. Also, ensure your young trees have plenty of sunshine.

Black Knot

Black knot is caused by tree fungus, which causes galls and black bulging on trees and plants. In springtime and summer, the fungi release spores from the galls and infect new branches, particularly in humid conditions. The disease affects fruit trees like plum, cherry, blooming almond, blackthorn, and apricot.

Trees may develop brown bulgings on the branches or trunks during the first year of infection. In the following year, the swellings create black galls around the stem and the surface of the tree may break or split. If galls encircle trunks or major limbs, a serious black knot infestation can kill a tree.

The simplest strategy to avoid this widespread tree disease is to trim any affected stems and branches as soon as you notice them.


Anthracnose is a prevalent disease that affects most types of trees, particularly ash, sycamore, and oak. It also harms bushes like privet, resulting in ugly black, recessed lesions on the leaves, branches, flowers, and fruits.

Because anthracnose fungus requires water to proliferate and infect, the illness is more common during damp, chilly springs. Anthracnose is typically not treated since it is a cosmetic issue rather than a major danger to tree health.

Cultural control activities such as removing and disposing of twigs and leaves, enhancing air circulation by tree trimming can help avoid the condition. Taking care of your trees can encourage them to develop healthily and fill up your yard.

Canker Infection

Trees are affected by several canker diseases, such as Cytospora canker on poplar, pine, willow, and spruce. Canker illnesses occur when an infection, either bacterial or fungal, penetrates the bark through a wound.

Ultimately, the tree’s vascular system gets obstructed, preventing nutrients from flowing. This obstruction might cause branches to perish based on where the canker is located. If it wraps surrounding the trunk, the whole tree may perish.

Trees which are strained from environmental variables, animals, mechanical damage, or other causes are more vulnerable. Preventative strategies like growing trees appropriate for the available conditions, preventing bark injury, correct tree care, wintertime protection, and pruning any canker-affected branches. For serious infection, consider tree cutting. 

Get Professionals to Control Tree Diseases Before They Get Worse

Hopefully, the guide above can help you identify common diseases in your landscape.

At Top Notch Tree Service, we can help preserve your trees to be strong and healthy by preventing these tree diseases and more. Don’t allow diseases to ruin your favorite trees.

Contact us today for professional arborist services.