Aspen Leaf Galls: Phylloxera Insects and Simple Management

An aspen tree has pea-shaped, light green structures in rows along the leaf midrib on the underside. Leaves appear dry and moisture-depleted. The condition has recurred for years. The expert identifies these as likely Phylloxera galls—insect-induced growths.

What Are Phylloxera Galls?

Tiny aphid-like insects lay eggs on leaves; the plant responds by forming protective galls around them. The insects feed inside, but the impact on overall tree health is usually minimal if the tree is well-watered and fertilized.

Cultural Control

• Rake and destroy fallen leaves to reduce overwintering populations.
• Maintain tree vigor with proper watering and fertilization.
• No insecticide needed unless infestation is severe and tree is stressed.

Google “Phylloxera” for images to confirm the diagnosis. This is a cosmetic issue, not a tree killer.