In New Hampshire, the sugar maple is one of the most iconic and cherished trees, offering breathtaking fall color, maple syrup, and a vital role in our native ecosystem. But like all living things, even these hardy trees can suffer from disease. One of the most common and frustrating ailments affecting sugar maples in our region is Anthracnose, a fungal disease that causes leaf spotting, browning, and even premature defoliation.
What is Anthracnose?
Anthracnose is a fungal disease that thrives in cool, wet spring weather conditions that are all too common in New Hampshire. It infects young, tender leaves and shoots, causing irregular tan to brown blotches, curled leaf edges, and in severe cases, complete defoliation. Though sugar maples typically survive Anthracnose, repeated infections year after year can stress trees and leave them vulnerable to other pests and diseases.
Symptoms to Watch For:
- Tan to brown irregular leaf spots
- Curling or cupping of leaves
- Premature leaf drop (as early as late spring)
- Small twig dieback or cankers in severe cases
It’s often mistaken for frost damage or drought stress, so a professional diagnosis is essential for accurate treatment.
Is Anthracnose Deadly?
On its own, Anthracnose rarely kills a healthy sugar maple. However, chronic defoliation weakens the tree’s defenses over time. This makes it more susceptible to secondary invaders like insect borers, root rot, or verticillium wilt. That’s why addressing Anthracnose early and proactively can protect the long-term health of your trees.
Treatment Options
Controlling Anthracnose starts with good cultural practices, but for high-value or heavily infected trees, more targeted intervention is available.
1. Pruning & Sanitation
Remove dead twigs and branches, especially those showing signs of cankers. Rake and dispose of fallen leaves each autumn to reduce fungal spores that can overwinter in debris.
2. Improve Tree Health
Proper watering during drought periods, mulching to retain soil moisture, and avoiding lawn mower or string trimmer damage all help boost your tree’s natural resistance.
3. Trunk Injection with Propizol Fungicide
For trees experiencing repeated or severe outbreaks, trunk injection with Propizol (a propiconazole-based fungicide) is an effective treatment. This systemic fungicide is injected directly into the tree’s vascular system, allowing the active ingredient to travel throughout the canopy and stop the fungus from spreading.
Benefits of Propizol Injections:
- Delivers precise, internal treatment with minimal environmental impact
- Protects the entire canopy, not just surface leaves
- Lasts for one growing season and can be repeated annually if necessary
- Especially helpful for large, mature trees where spraying is impractical
Trunk injections should be performed by a licensed professional to avoid damaging the tree and to ensure accurate dosing.
When to Treat
Timing is critical—fungicide injections should ideally occur in early spring, just as the tree begins to leaf out. This allows the fungicide to move with the tree’s sap and protect the young, vulnerable foliage during the peak infection window.
Concerned About Your Sugar Maple?
If your sugar maple is showing signs of Anthracnose or has defoliated early in multiple seasons, it may be time for a professional assessment. At Belknap Tree and Plant our certified arborists can diagnose fungal infections and determine if a Propizol trunk injection is the right treatment for your tree. Contact us today to schedule a consultation and keep your trees healthy and thriving for years to come.