FIELD NOTES with MEL MACHADO
Defoliation Threatens Next Year’s Crop Much like spider mites, the most serious implications from red blotch result in defoliation of the current year’s foliage and the impacts on the following crop. Growers throughout the Central Valley are noting that their orchards are covered in spider mites. I’ve had many calls from growers asking what to do about their orchards that have lost most, if not all of their leaves. While it doesn’t necessarily mean that these orchards will not have a crop in 2027, the crop has a high likelihood of being adversely impacted. Premature defoliation reduces the tree’s ability to manufacture and store carbohydrates during the critical postharvest period. Those reserves fuel bloom, leaf-out, and early nut development the following spring. An orchard that loses significant leaf area before normal leaf drop can still produce a crop the following year but yield potential may be compromised.
Red Blotch Expands Across California Red blotch has become one of the most discussed issues of the 2026 season. First identified in a single Merced County orchard in 2024, this invasive fungal disease has spread throughout much of the San Joaquin Valley and into portions of the Sacramento Valley. University of California plant pathologist Florent Trouillas has documented both disease symptoms and effective management strategies. Multiple fungicide options are now available that can provide meaningful control when applied correctly. But judging from the number of orchards that are impacted by red blotch, it appears that many either made the economic decision not to treat, missed the proper treatment timing, or were impacted by late season rains that promoted the production of additional spores, leading to late infections. As I fly around the valley, I’ve noticed that the reddish hue in orchards with advanced infection is visible from the air.
Red Blotch Damage. Photo credit: Mel Machado
Severe Red Blotch Infection Leading to Defoliation. Photo credit: Mel Machado
Low or No-Care Orchards Serve as Sources of NOW. Photo credit: Mel Machado
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ALMOND FACTS
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