Red Leaf Blotch: A New Threat for California Almond Orchards

We just received a note from the Almond Board of California alerting growers to a new almond disease: red leaf blotch. First detected in Merced County in May 2024, it’s now present across all major almond-growing regions. The disease isn’t lethal, but it weakens trees by reducing canopy health, photosynthesis, and next year’s bud development.

Symptoms appear from late April to mid-May, starting as small yellow spots that expand into orange or reddish-brown blotches. Leaves may curl, scorch, and drop early. Several key varieties are affected, including Nonpareil (non-puh-REL), Independence, and Monterey.

Because infection occurs weeks before symptoms appear, researchers stress preventive fungicide use. They recommend a three-spray program to keep orchards protected. UC Cooperative Extension also urges growers to remove or break down infected leaf litter before the next season.

Scouting should begin in early May, with suspected cases reported promptly to UCCE farm advisors.

For the note from the California Almond Board, visit: https://www.almonds.com/almond-industry/industry-news/preventative-fungicide-treatments-key-managing-red-leaf-blotch-almond?utm_medium=enewsletter&utm_source=InTheOrchard&utm_campaign=us+ic&utm_content=Article&utm_term=IPM