6 Fungal Diseases to Look Out for this May

April showers bring May fungal disease isn’t the saying most people are used to hearing, but it’s accurate. The wet weather and cool nights we experienced this April were perfect breeding grounds for fungi to grow and infect trees. Now that the weather is heating up many homeowners are noticing signs of fungal diseases on their trees and shrubs. Learn which fungal diseases to look out for this May/June and how to keep your trees/shrubs safe.

1. Anthracnose

dogwood anthracnose

Anthracnose is a tree fungus that is active in the spring when the weather is wet and cool. Overwintering in fallen leaves, this fungus will continue to infect your tree year after year if not treated. Multiple infestations can leave trees stressed and susceptible to secondary invaders.

Targets: Dogwoods, Ash, Oak, Sycamore, Birch, Walnut, Tulip, Hickory, and Maple


  • Tan or brown leaf spots which many have purple rings around them
  • Wilting
  • Defoliation
  • Leaf blotches.

*In the spring our arborists see a TON of Dogwood Anthracnose. If you have a dogwood (with the exception of Kousa Dogwoods), your tree should be on a preventative fungicide treatment this spring*

Learn more about Dogwood Anthracnose

2. Shot Hole Fungus

This tree fungus is commonly mistaken for insect damage because of the BB-sized holes it leaves.  This fungus will stress your plants and should be treated to keep secondary invaders away.

Symptoms: Brown or reddish-brown leaf spots, holes in leaves where the leaf spots used to be, yellow leaves dropping in mid-summer.

Targets: Cherries, Cherry Laurels, Roses

3. Phytophthora Root Rot

Phytophthora Root Rot is an extremely damaging and widespread fungus-like organism that will rot away root systems and eventually kill your tree if left untreated. In the worst cases, when left untreated trees can become structurally unsafe and uproot or snap possibly causing property damage and injury.

Symptoms: Suppressed growth, yellow or undersized needles/leaves, dieback, drooping and curling of leaves, leaves turning brown.

Targets: A wide range of plants. The most susceptible include Azalea, rhododendron, dogwood, pieris,  yew bushes, deodar cedar, mountain laurel, heather, juniper, Fraser fir, white pine, shortleaf pine, camellia japonica, aucuba.

Learn more about Phytophthora Root Rot

4. Cercospora Leaf Spot

The tree fungus begins as a small spot on the leaves. As the disease progresses more spots appear until the leaf ceases to function as the site of the tree’s food production process and falls off of the tree.

Symptoms: Round leaf spots (may have purple or dark brown borders), tiny black flecks (fungal spores) in the center of the spots.

Targets: Wide range of ornamentals, shade trees, and plants. Our Arborists report that White Oaks are especially susceptible in our area.

Learn more about Cercospora Leaf Spot

5. Powdery Mildew

Powdery Mildew is a tree fungus that coats leaves blocking the process of photosynthesis.  Every year trees and shrubs rely on photosynthesis to create food for new leaf growth. When this process is interrupted by powdery mildew the food reserves aren’t replenished and the tree/shrub’s growth will be stunted which can affect overall health. The stress caused by Powdery Mildew also makes the tree more susceptible to other diseases and insect infestations.

Symptoms: Powdery mildew is characterized by spots or patches of white to grayish, talcum-powder-like growth on the upper side of leaves.

Targets: A wide range of plants but Lilacs, Peonies, Dogwoods, or Crape Myrtles are especially susceptible in this area.

Learn more about Powdery Mildew

6. Sooty Mold

Sooty mold is a fungus that grows on top of honeydew (the excrement of plant-sucking insects) and coats the leaves to the point where they can no longer absorb sunlight. This interrupts photosynthesis and the tree will not be able to produce the nutrients they need for survival. If your trees and shrubs are turning black you most likely have a sooty mold problem caused by an insect infestation.

Targets: Typically seen on rose, ash, oak, elm, maples, willow, and fruit trees.

Have you noticed any of these diseases on your trees and shrubs? We can help! Give us a call at 703-573-3029 or schedule an appointment online to meet with a Certified Arborists. They will be able to diagnose your fungal issue and create a treatment plan.

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