Black Knot on Flowering Almond: Prune Out Galls, Sterilize Tools

Hard Black Galls on Almond = Black Knot Fungus

A pink flowering almond shows thick dark crusty growths on trunk/branches, leaves only at tips, flowers shriveling. Diagnosis: Black knot (Apiosporina morbosa).

Disease Cycle

Spores infect wounds in spring. Galls swell over 1–2 years, releasing olive-green spores next spring. Spreads to new twigs. Can girdle and kill branches.

Control

• Prune: Cut 4–6 inches below each gall. Late winter (dormant) best.
• Destroy: Burn or bag prunings—don't compost.
• Sterilize: Tools between cuts (10% bleach, 70% alcohol).
• Fungicide: Chlorothalonil or thiophanate-methyl at bud break + 2 wk intervals (supplemental).

Susceptible Species

All Prunus: cherries, plums, apricots, almonds. Check nearby plants.

Reference

NCSU: ces.ncsu.edu/depts/pp/notes/oldnotes/fd4.htm