Often, people report that their tree is sick, losing its leaves in summer. The key question is whether it is a fruit tree, such as a crabapple or an apple tree. In most cases, the issue is scab.
Scab, one of the most common fungal diseases, is caused by the fungus Venturia inaequalis.
The disease appears as circular lesions, often black or brown, on the leaves. Spring weather plays an important role, as cool temperatures and rain favor infections.
A severe infection can lead to significant defoliation. Generally, apple scab does not kill trees, but it weakens them, making them more vulnerable to other insects and diseases.
Pruning trees to allow air and light penetration helps reduce this issue.
Avoid drastic pruning and excessive nitrogen fertilizers, which promote the rapid growth of tender shoots that are more susceptible to infection.
Never compost infected leaves or plant debris. Collect and dispose of infected leaves and fallen fruit by discarding them in the trash or burning them as quickly as possible.