Subject: UNH Extension Infoline: Regarding your backyard tree inquiry

Hello Jeremy,

Thank you for contacting the UNH Extension Infoline regarding the issues you are experiencing with your backyard tree. Following up on your email from 7/15/2026, I have put together some information below to help get you started.

Based on your description and geographic location, your tree is very likely suffering from apple scab (assuming it is a crabapple tree). This is a highly prevalent fungal disease common to older, susceptible crabapple varieties across New England. Information regarding this condition and its management is primarily sourced from authoritative regional agricultural extensions, specifically the University of New Hampshire Extension and the University of Vermont Extension. You can read their detailed guides here:

• UNH Extension: Apple Scab Fact Sheet
• UVM Extension: Early Defoliation of Trees

Why This Is Happening

• The Fungus: Apple scab is caused by the fungus Venturia inaequalis. It overwinters on fallen, infected leaves beneath the tree.
• Weather Triggers: During cool, wet New England springs, fungal spores shoot up into the air and land on emerging leaves. This explains why the tree's health fluctuates year-to-year based on seasonal rainfall.
• The Leaf Drop: The fungus forms dark spots on the leaves, disrupting photosynthesis. As the infection worsens by mid-to-late summer, the leaves turn yellow and prematurely drop to the ground.
• Reduced Blooming: Because the tree loses its leaves early every summer, it cannot store enough energy through photosynthesis to produce heavy flower displays the following spring.

How to Support Your Tree

While this disease is highly frustrating and causes an eyesore, the good news is that it rarely kills the tree outright. You can take action to support its health:

• Sanitation (Most Important Task): Thoroughly rake up, bag, and destroy all fallen leaves and debris beneath both affected trees this autumn. Do not compost them, as the fungus will survive the winter and reinfect the new spring leaves.
• Winter Pruning: Prune the inner canopy of the trees during the winter dormant season. Removing crowded branches opens up the canopy to let sunlight and wind move through, which helps the leaves dry faster after spring rains and reduces fungal growth.
• Spring Preventative Spraying: Once the leaves begin turning yellow in the summer, it is too late to spray curative chemicals. If you choose to use fungicides (such as chlorothalonil or copper sulfate), they must be applied protectively in early spring as the flower buds just begin to show color.
• General Vigor Care: Avoid additional environmental stress by watering the tree deeply during prolonged periods of summer drought.

Consider Preventative Treatments

• Apply preventative fungicides if you wish to retain the existing trees. Spraying infected leaves right now will not cure them, but a preventative fungicide program can protect next year's growth.
• Time the applications perfectly starting early next spring at "green tip" (just as the leaf buds break) and repeating every 7 to 14 days until roughly two weeks after flower petals fall. Always follow product labels carefully and avoid multi-purpose fruit sprays that harm vital pollinators.
• Consult a certified arborist for assistance or if the trees are too tall to spray safely, as they can evaluate systemic trunk injections.

For additional localized assistance and detailed identification guides, you can review the UNH Extension Apple Scab Fact Sheet.

We are committed to finding the right solution for your lawn and garden and are happy to provide further guidance as needed. Please feel free to reach out with any further questions .

Best regards,

Best regards

Haim
Master Gardener Volunteer
UNH Extension Infoline Team