Although spring just began, our arborist warn homeowners to already be on the lookout for fungal leaf diseases. Fungal diseases that attack the leaves of trees can start emerging as early as buds start to sprout and new growth begins. Our current weather conditions, rainy with warmer days and cool nights, are perfect breeding grounds for all types of fungal diseases, especially fungal leaf diseases.
When it comes to fungi, prevention is key. Usually once you see the symptoms of leaf diseases it is too late to reverse the damage that has already been done. However, you can stop the disease from progressing and protect next years growth by still treating your trees after you notice symptoms and signing up for a preventative program for next spring.
If My Tree Had A Fungal Leaf Disease Last Year. Do I Need Preventative Treatments This Year?
Yes, If your tree has suffered from fungal leaf disease in the past or is showing signs of infection this year you should start preventatively treating your tree every spring. Once your tree has been infected with a fungal disease it will most likely keep getting infected year after year. This is because the fungal spores overwinter in the soil, mulch, and leaf debris. They are awakened in the spring by rain and easily reinfect the tree(s).
Signs Of Fungal Leaf Diseases
Round Leaf Spots
If your trees and shrubs are starting to develop round spots on their leaves they may be suffering from Cercospora Leaf Spot. This leaf spot disease creates small spots on leaves that may have purple or dark brown borders and tiny black flecks (fungal spores) in the center of the spots. A wide range of ornamentals, shade trees, and shrubs are susceptible to this fungal leaf disease; however, our arborists report that white oaks are especially susceptible in our area.
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.
Learn more about Cercospora Leaf Spot
Brown Near The Vein/Brown or Yellow Leaf Spots
If your trees and shrubs are starting to develop blotchy yellow or brown leaf spots it may be suffering from Anthracnose. Typically these spots will have purple rings around them. Other symptoms include wilting, defoliation, and dieback.
The flowering dogwood is one of the most susceptible trees to anthracnose. Other target trees include ash, oak, sycamore, birch, walnut, tulip, hickory, and maple.
Learn more about Antracnose
If your trees and shrubs are starting to turn black you most likely have an issue with 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.
This disease is typically seen on rose, ash, oak, elm, maples, and fruit trees but can attack any species.
If you’re tree has spots or patches of white to grayish talcum-powder like growth on the upper side of leaves it’s most likely suffering from 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’s/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.
Powdery Mildew attacks a wide range of plants but Lilacs, Peonies, Dogwoods, or Crape Myrtles are especially susceptible in this area.
Learn more about Powdery Mildew
Reddish Brown Spots/Holes In Leaves
If you see small reddish-brown spots on your leaves or BB-sized holes in your leaves you are most likely dealing with Shot Hole Fungus. This foliar tree fungus is commonly mistaken for insect damage because of the BB-sized holes it leaves. As the fungus progresses the leaves will begin to turn yellow and drop in mid summer. This fungus will stress your plants and should be treated to keep secondary invaders away.
Shot Hole fungus tends to target Cherry Trees and Cherry Laurels.
Learn More About Shot Hole Fungus
Any Other Type Of Spots On Tree Leaves
Above we’ve covered some of the most common leaf spot diseases caused by spring fungi; however, if your tree has leaf spots that do not look like any listed above still give us a call. Your tree could be suffering from one of the less common leaf fungal spot diseases and still should be treated.
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How To Treat Fungal Leaf Diseases
If your tree starts to show symptoms of fungal leaf diseases, our Arborist will identify the disease and come up with a series of treatments that will most effectively treat the tree this year and prevent the tree from contracting the disease again next year. These treatments will most likely consist of fungicide treatments as well as supporting treatments to boost the overall health of the tree, such as bio-stimulants, aeration, and pruning.
Can I Just Apply Fungicides Myself?
Although it seems like an easy solution to just by fungicide from a nursery or home improvement store, this is typically a very bad idea. Our arborists strongly advise against trying to DIY when it comes to tree disease treatments for a few reasons.
When fungicides are not applied properly they can be detrimental to the health of the tree, the individual applying them, the surrounding wildlife, and the environment.
Improperly applied fungicides or fungicides applied in the wrong weather conditions can lead stormwater pollution, poisoning of the food/water supply for local wildlife, shocking the trees system and reducing its overall health, and adverse side effects for the person applying the treatment.
Not As Effective:
The treatments you can by in stores typically aren’t as effective. Treatments you are allowed to purchase without a license aren’t as strong and don’t contain all of the same ingredients as treatments that tree service companies use. In order for these treatments to be sold to the general public they have to be weakened and watered down in order to meet federal and state regulations. Because of this, these treatments aren’t as effective in treating fungal leaf diseases, or any tree diseases in general.
Secondly, the treatments you can purchase in stores aren’t targeted. Certain fungicides work better on certain types of fungal disease. This means that the general fungicide you purchase at your local home improvement store or nursery may be useless against the type of fungal disease your tree has.
So leave it up to the experts, if your tree is showing signs of fungal leaf disease, or you’re interested in preventative treatments schedule an appointment with one of our arborists online or give us a call at 703-573-3029.