In California’s sun-soaked vineyards, where the wine and table grape industries are cornerstones of the state’s agricultural economy, powdery mildew remains a relentless adversary. Caused by the fungal pathogen Erysiphe necator, powdery mildew is one of the most pervasive and damaging diseases in viticulture, affecting both the yield and the market quality of grapes.
Once established, powdery mildew spreads rapidly, producing a characteristic white, powdery coating across leaves, shoots, and fruit. Beyond its visual symptoms, the disease can severely compromise vine function—distorting leaves, scarring fruit, and reducing sugar accumulation, all of which pose significant threats to both growers and winemakers.
Conventional Control and Emerging Challenges
Traditionally, powdery mildew has been managed through a combination of cultural practices, resistant cultivars, and fungicide applications. Preventive fungicides such as sulfur and biologicals are commonly used as protectants, while eradicants—including horticultural oils and potassium bicarbonate—are employed when infections are already visible. However, repeated use of these chemicals raises concerns about environmental impact, pesticide residues, and, increasingly, pathogen resistance. With the pressure mounting to find sustainable, effective, and residue-free solutions, attention has turned to novel technologies that offer both performance and environmental compatibility.
Introducing Mineral Oxychloride (MOCl) Technology
A promising alternative is emerging in the form of JC 9465 Mineral Oxychloride Solution (MOCl), a proprietary advanced oxidation reagent developed for agricultural applications. MOCl functions through the generation of high levels of reactive oxygen species (ROS), which target and destroy microbial cells by oxidative stress rather than chemical toxicity.
In the summer of 2024, a field study was conducted on a commercial vineyard in Fresno County, California, specializing in Crimson Seedless grapes—a Vitis vinifera cultivar with a documented susceptibility to powdery mildew, particularly during the latter part of the growing season. The goal was to evaluate MOCl’s efficacy in managing powdery mildew in a real-world, production-scale environment.
JC 9465 MOCl solution is:
- EPA-registered as a biocide.
- NSF-certified for use in potable water systems.
- Certified organic, and approved for applications in organic agriculture.
- Classified as safe for human consumption, with no pesticide residue or withholding period.
Importantly, unlike conventional fungicides, microorganisms cannot develop resistance to oxidative stress, making MOCl a compelling option for integrated pest and disease management (IPDM) programs.
STUDY: Evaluation of Mineral Oxychlorides for Powdery Mildew Control in Grapes
Powdery Mildew (Erysiphe necator) is a prevalent fungal disease in grape production, significantly affecting yield and fruit quality. This study aimed to evaluate the performance of a mineral oxychloride-based formulation (MOCl) in controlling powdery mildew.
- Study Location: Clovis, California
- Crop: Grapes (Vitis sp., cv. Crimson)
- Target Disease: Powdery Mildew (Erysiphe necator)
- Study Duration: April 24 – October 4, 2024
- Application Frequency: 7 applications from April to October 2024, approximately every 7–10 days
- Application Method: Mist blower at 100 gal/acre at a dosage of 400 PPM
- Experimental Setup: 4 treatments, 4 replications, 3 vines per plot
- Assessment Parameters: Disease incidence on leaves and bunches, bunch rot at harvest, phytotoxicity
Observed Advantages of JC 9465 Mineral Oxychloride Agent
- Effective Disease Suppression
MOCl significantly reduced powdery mildew incidence and severity across all observation dates:
- Leaf Infection Reduction:
- From 58% (untreated) to 34% after 3 applications.
- From 73% (untreated) to 38% after 4 applications.
- Bunch Infection Suppression:
- Reduced mildew severity from 49% (untreated) to 35% after 6 applications.
- Reduced and maintained severity from 59% (untreated) to 30% one month after the last application.
- This translates to approximately 50% reduction in disease pressure, confirming MOCl ability to effectively suppress powdery mildew in field conditions.
- Reduced Postharvest Bunch Rot
At harvest, MOCl-treated plots showed a marked reduction in bunch rot:
- Rot in untreated plots: 31.3%
- Rot in JC 9465 plots: 16.3%
This represents a nearly 50% decrease in bunch rot, an important quality and shelf-life factor for fresh-market grapes.
- No Observed Phytotoxicity
Across all evaluation dates, JC 9465 exhibited zero phytotoxicity, even with repeated applications. This suggests excellent crop safety, allowing for its integration into intensive spray programs without risk of plant damage.
- Comparable Performance to Sulfur with Additional Benefits
On a side-by-side comparison with sulfur (Microthiol Disperss), JC 9465 MOCl delivered :
Similar disease suppression
Better performance under high disease pressure
Easier handling and potential for reduced sulfur-related vine stress
Conclusion
JC 9465 mineral oxychloride-based agent demonstrated reliable and consistent control of powdery mildew in grapevines. With its:
- Proven efficacy against leaf and bunch infections
- Substantial reduction in bunch rot
- Zero phytotoxicity over a full season
- Performance comparable to sulfur, with enhanced safety and handling
Mineral oxychloride solutions are a viable and valuable addition to integrated grape disease management programs. It is particularly suited for growers seeking an effective, non-phytotoxic alternative to sulfur or rotating fungicides to mitigate resistance development. JC 9465 MOCl technology offers a sustainable and scalable solution for vineyard disease management, particularly suited for organic operations or those seeking to reduce dependence on synthetic fungicides. Its mechanism of action—through oxidative degradation rather than toxicity—presents no risk of pathogen resistance development, a critical advantage as resistance to commonly used fungicides becomes increasingly problematic. As California grape growers continue to navigate climatic variability, regulatory pressure, and market demand for low-residue fruit, innovations like mineral oxychloride represent a timely and promising addition to the viticultural toolkit.
By Charles Jennings, Jenfitch Inc, Walnut Creek, CA
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