Orchard Sanitation Sanitation plays a moderate role in controlling red leaf blotch by reducing the amount of fungal spores available to infect next year’s crop. UC Cooperative Extension recommends removing or breaking down infected leaf litter before the next season. This can be done by mowing or shredding leaves in the fall or winter. Applying urea or other nitrogen- rich materials to leaf litter can speed decomposition, helping to suppress the fungal population. If conditions allow, incorporating the leaves into the soil through light tillage can also be beneficial. It’s important that growers avoid transporting infected debris or equipment from one orchard to another. Tools, trailers or bins that have had contact with infected plant material should be cleaned before moving to new sites. The more growers in a region who follow these sanitation practices, the more effective they will be since spores can easily move on wind or rain between neighboring blocks. Monitoring and Research Growers should begin scouting for symptoms in early May and report any suspected cases to their local UCCE farm advisor. Early reporting helps researchers better understand the disease’s spread and behavior in California growing conditions. Research led by Trouillas and his team at UC Davis is ongoing. They are currently studying fungicide efficacy, timing of spore release and host susceptibility, environmental triggers, and how different almond varieties respond to infection. They are also developing improved diagnostic tools to help detect the disease earlier in the season. Red leaf blotch is a new disease for California almond growers, but with early action and coordinated management, it can be kept under control. Preventive fungicide sprays, diligent orchard sanitation and regional cooperation are the best tools currently available. Stay in touch with your local UCCE advisor and watch for further updates as more research results become available. Article Contributed by the Almond Board of California
Red Leaf Blotch Tight
Red Leaf Blotch Medium
Red Leaf Blotch Wide
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SEPTEMBER–OCTOBER 2025
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