What Causes Black Spots on Tree Leaves?  

Black leaf spots may appear on your plant for various reasons. When you notice black spots on tree leaves, the most common culprit is the black spot fungus or disease.   

In this post, we discuss how to diagnose, prevent, and treat black spot disease, as advised by the best tree removal company in Folsom, CA.

black spots on tree leaves



Black spot disease presents as black or brown spots on leaves. You can distinguish black spot fungus from other diseases by its dark black color and fringed edges. In warm and humid conditions, the fungus can attack any plant with fleshy leaves and stems, from the maple tree to the rose shrub.   

Black spot fungus begins to develop in the spring, typically starting with tiny black spots that grow bigger as the fungus develops. Left untreated, the entire leaf turns yellow and falls.  

Black Spot Fungus Disease Life Cycle 

While black spot fungus variants exist, each attacks only one or a few tree species. However, they have similar life cycles:  

  • Overwintered spores travel by wind, either from the fallen leaves or from crevices in the affected tree’s bark and branches.  
  • Carried by water or wind, the spores stick to leaves and start growing.  
  • They survive the cold in the fall because the fallen leaves form an insulating barrier, or the tree bark they’re nestled in shields them from the elements. New spores develop at this stage.  

Prevention and Treatment of Black Spots on Tree Leaves  

Unlike common tree diseases, black spot fungus will rarely kill the host plant. However, treating black spots requires diligence. You have several options for dealing with black spots on tree leaves.

Prevention beats cure. Inspect the garden regularly in the spring and consider preventive spraying before temperatures hit 60 degrees. Black spot disease spreads fast, so you should start preventive spraying before the environment becomes conducive for black spot fungus to thrive.  

For prevention, spray the tree with a Bordeaux-type treatment when winter ends or at the very beginning of spring. You also want to exercise good garden hygiene and maintain healthy trees.   

Ensure the trees get sufficient sunlight and good circulation, remove garden litter, and avoid overhead watering, especially on cloudy days. During an outbreak, dispose of all affected debris. Throw or burn the debris because spores can overwinter on plant material like fallen leaves but can’t survive on bare soil.   

Burning is effective, but composting also works well because the heat and bacteria destroy the spores before they get a chance to spread.   

As a curative care measure, spray the infected tree with a natural fungicide. With so many treatment options on the market, read the label instructions for the method you choose and follow them closely.  

Are you looking for an all-natural treatment option? Consider neem oil, not only for its effectiveness against black spot fungus but also as a method to treat aphids on trees, which can be another common issue in garden care. Pressed for an evergreen tree, neem oil has shown impressive results as an effective garden fungicide.  

You also want to prune infected trees to promote healthier growth come spring. Don’t forget to disinfect your pruning tools before and after to prevent spreading the disease to healthy plants.  

Contact Your Local Tree Experts  

When you need professionals that you can count on to handle any tree care job with integrity, look no further than Ace Tree Service. We guarantee the highest standards of safety and quality when providing various tree care solutions, including:  

  • Defensible space cleaning  
  • Emergency storm services  
  • Stump grinding and root removal  
  • Tree removal  

Don’t hesitate to reach out for more information about black spots on tree leaves or how to treat and prevent tree decay. Call us at (916) 934-3204 for a free quote.