Anthracnose
Anthracnose
Anthracnose is a fungal disease that is transmitted by air and typically occurs in Maples and Ashes. While it is usually classified as more of a cosmetic or nuisance type issue, it can cause large amounts of premature leaf drop and amount to substantial defoliation, which can be concerning.
This disease can kill twigs and branches, causing damage to these trees and resulting in disfigured characteristics after years of repeated infections. Fortunately, most trees that drop their leaves early will grow new shoots and foliage by mid-summer. If sufficient fertilization is provided to maintain vigor and proper root energy, healthy trees will usually withstand repeated defoliation for years without serious consequence.
Symptoms
Symptoms range greatly from small tan, dark brown, or black spots that appear circular (or not) to larger blotches on the leaves. Young, infected leaves may also distort in shape due to abnormal growth, and usually quickly succumb and drop following the heavy infection.
Causes
- Long periods of wet weather
- Poor air circulation in thick or dense foliage
Treatment & Prevention
- Regularly clean up (and destroy) fallen leaves to eliminate a place of anthracnose spores.
- Use a proper arborist to prune your tree and improve air flow and light penetration in the canopy.
- Keep your tree healthy with proper watering practices (at the dripline, not the leaves) and a well-thought-out fertilization program.
Fertilizing Method
Fertilization is usually done with hydraulic injection and will be performed around the tree’s dripline, roughly 12 to 16 inches below ground level, using a slow-release NPK fertilizer (30-8-8 NPK). This is a minimally invasive procedure and should be repeated every other Spring until the tree has made a full recovery. Recovery can take a few years, depending on the condition of the tree, and stopping the fertilizer can be detrimental to the tree’s health, or it can create a condition for anthracnose to continue or worsen.
Note: There can be environmental conditions noted where certain trees have anthracnose that will never go away.