ISA Certified Arborist Practice Exam

What can leaf scorch indicate about a tree's condition?

1. Excessive watering

2. Root disease or drought

3. High nutrient levels

4. Insect infestation

The correct answer is: Root disease or drought

Leaf scorch is a physiological condition that typically indicates stress in a tree, often linked with root issues or insufficient water supply. When a tree experiences drought, it fails to take up adequate water and begins to conserve moisture by closing its stomata, which can lead to the browning and wilting of leaves at the edges. This condition is exacerbated if there is a root disease, as damaged roots can further hinder water uptake, resulting in symptoms consistent with leaf scorch. The other options do not correlate directly with the symptoms of leaf scorch. Excessive watering can lead to root rot rather than scorching, high nutrient levels usually result in overly lush growth rather than stress symptoms like scorch, and insect infestations generally cause different types of damage that wouldn't typically present as leaf scorch. Thus, the connection between leaf scorch and water-related stress provides insight into the overall health of the tree, making the identification of root disease or drought the most accurate interpretation of this phenomenon.