Ash anthracnose, Gloeosporium aridum, is a fungal disease that infects ash trees causing dead lesions on leaves. These lesions disrupt photosynthesis and transpiration, which can lead to early leaf drop in the spring, although a second flush of leaves soon follows. Thicker, mature leaves are less susceptible to ash anthracnose infection. Multiple years of defoliation from ash anthracnose can reduce tree health and predispose trees to other insects and diseases.
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Treatment Strategy
There is no cure for ash anthracnose once the infection has occurred, so protecting newly emerging foliage with a fungicide is the best preventative measure. Foliar sprays with fungicides are used in the spring as leaves are emerging and again 14-21 days later to prevent infection. The timing of these applications is critical to ensure good control. Foliar sprays on large trees can be a challenge.
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Ash Anthracnose Treatment Option 1
Application Method – Foliar spray
DIY Equipment/Product Needed:
• Hand pump sprayer with wand
• Gloves
• Safety glasses
Ash Anthracnose DIY Kit
Application Method – Foliar spray
DIY Equipment/Product Needed:
• Hand pump sprayer with wand
• Gloves
• Safety glasses
How Is It Spread?
During rainy and relatively cool periods in the spring, ash anthracnose spores germinate and the fungi penetrate the leaves. New infections and the spread of existing infections stop when the weather becomes hot and dry. This pathogen overwinters in twigs, petioles, leaf veins, and seeds.
Susceptible Trees
Symptoms
- Large tannish-brown, irregular lesions occur in the spring on expanding leaflets – especially along margins and veins.
- Leaves may become twisted and wrinkled.
- Early leaf drop, particularly from the lower parts of the canopy.
Related/Similar Problems
Timing
Spring
Urgency
Moderate
Risk of Spreading
Moderate
