Red Bumps on Autumn Blaze Maple: Leaf Spot or Gall?

Two Possibilities

A 2-year-old Autumn Blaze maple shows hard red bumps on most leaves.

1. Phyllosticta Leaf Spot (Fungus)

• Circular tan spots with purple-red borders.
• Black fruiting bodies in rings later in season.
• Infects late season; minimal damage, maybe early leaf drop.
• Fungicides (mancozeb, chlorothalonil) only if applied preventively in spring—not worth it for slight cosmetic issue.

2. Leaf Gall (Tiny Wasp)

• Wasp lays eggs; leaf forms gall around them.
• No harm to tree health.

Verdict

Neither requires treatment. The tree may lose some growth or drop leaves slightly early, but overall health is unaffected. Ignore it.