Clean Vines, Strong Future: Why Clean Plant Material Matters More Than Ever

Planting a vineyard is one of the most important—and expensive—investments a grower can make. Every decision made at the outset sets the stage for decades of vineyard health, productivity, and economic viability. At Napa Valley Grapegrowers, we believe that choosing clean plant material is a fundamental step in ensuring the long-term success of your vineyard—and protecting the resilience of the entire region.

What Is "Clean Plant Material"?
“Clean” means plant material that is tested and verified to be free of known viral pathogens and damaging pests. That includes both scion wood and rootstock. It also means the nursery has followed rigorous sanitation and propagation protocols to minimize the risk of contamination from viral, bacterial, fungal, or insect vectors.
Diseases like Grapevine Red Blotch Virus (GRBV), Grapevine Leafroll-Associated Viruses (GLRaVs), and fungal trunk pathogens continue to impact vine longevity and grape quality in California. Even vines that appear healthy can harbor pathogens—making certification and testing essential.

Why It Matters: Economics, Environment, and Equity

• Economic: Replanting due to infected vines can cost $25,000–$50,000 per acre and delay full productivity for 3+ years.
• Environmental: Replanting early wastes water, diesel, fertilizers, and soil amendments—all inputs with a carbon footprint.
• Community Impact: Lost revenue can reduce farmworker hours, disrupt contracts, and strain vineyard operations.

Clean material isn't just about vine health. It’s about building resilience into our farms, our businesses, and our shared agricultural landscape.

Best Practices for Sourcing Clean Plant Material​: 
1. Vet Your Nursery—Ask Around 
Do your homework. Ask other growers which nurseries they trust—and why. A nursery’s reputation, transparency, and past performance are strong indicators of the health of their stock.
2. Schedule a Visit 
Go see it for yourself. Visit your nursery’s increase blocks and propagation facilities—especially in fall when viral symptoms are more likely to be visible. Look for consistent sanitation practices, clear labeling, and healthy vines.
3. Prioritize CDFA-Certified Material
Nurseries participating in the California Grapevine Registration & Certification (R&C) Program follow established virus testing protocols. Certification doesn’t mean virus-free, but it significantly lowers your risk.

• Learn more about CDFA’s R&C program: CDFA Regulations for Grapevine Certification

4. Be Extra Cautious with Field-Selected Budwood
Field selection is common, especially when growers want to preserve specific clonal material. But viruses can be latent. If using this approach, test with a certified lab and work with FPS to ensure safe propagation. Don’t rely solely on visual symptoms.
5. Know the Source Block's Age and History
Recently released Foundation Plant Services (FPS) selections have likely undergone more thorough testing using modern techniques (e.g., PCR). Older blocks may carry latent viruses not screened for in past decades.
6. Prefer Primary Increase Blocks
Primary increase blocks are closer to the original clean source material and face fewer opportunities for reinfection compared to secondary blocks. Ask your nursery what stage the plant material comes from.
7. Ask for and Review Testing Protocols
How many samples are taken? Are they composite or individual? What methods are used (PCR, ELISA, biological indexing)? Was material tested at the right time of year for target viruses? You’re entitled to this information—ask for it.

• Spring: Ideal for Grapevine Fanleaf Virus
• Dormant canes: Best for Leafroll, Vitiviruses

If the material hasn’t been tested recently, request samples and send them to a trusted lab.
8. Avoid Brokered or Third-Party Material
When nurseries outsource plant propagation, it introduces more variables and less control. If brokered material is your only option, ask to inspect the site and request the same records you’d expect from a primary nursery.
9. Avoid Secondary Increase Blocks
Secondary blocks are more likely to become reinfected. These vines are further removed from the foundation material and more susceptible to environmental or handling-related contamination.
10. Don’t Buy Held-Over Vines
If vines didn’t sell last season and were held in cold storage, their vigor may be reduced—and their exposure to pathogens may have increased. Always ask when your vines were propagated.
11. Inspect Performance in Other Vineyards
Seeing is believing. Ask the nursery for client references and visit vineyards that were planted with the same material. How do the vines look? How is fruit quality? Are there any symptoms of decline?
12. Hire a Consultant to Grade the Vines
A seasoned viticultural consultant can spot quality concerns before vines leave the nursery. This modest investment can save you tens of thousands of dollars down the road.

Understanding Certification Levels

Classification                                  What It Means
Non-Certified (NC)                         - Tested by the nursery—not inspected by CDFA.                                                                       Protocols vary. Ask for full transparency.
Certified (C)                                   - Tested and inspected by CDFA under R&C program.                                                                 Includes known pathogens like Red Blotch.
Protocol 2010 (P2010)                  -  Top-tier material. Meristem tissue cultured and tested                                                              using advanced diagnostics (PCR, ELISA, indexing).                                                               Rare and premium-quality.
Learn more about FPS Protocol 2010

It’s Not Just Viruses: Watch for Pests and Fungal Pathogens

• Vine Mealybug (VMB): Once introduced via nursery stock, VMB has become one of the most persistent vineyard pests in California. Hot water dips and systemic insecticides have reduced the threat—but don’t skip visual inspection of shipments.
• Trunk Diseases: Fungal pathogens like Eutypa, Botryosphaeria, and Phaeoacremonium can spread during the propagation process. Their presence is strongly linked to vine decline within the first 5–10 years of planting. Clean cuts, sterilized tools, and heat treatments are essential prevention tools.

A Warning from the Past: The EGVM Lesson
In 2010, the European Grapevine Moth (EGVM) appeared seemingly overnight in Napa County. Over 100,000 moths were trapped that year alone. The source was never confirmed—but untested imported plant material is a suspected vector. Through valley-wide collaboration and years of diligence, Napa was declared free of EGVM by 2016.
It’s a success story—but also a cautionary tale. The choices we make today affect the health of the region for years to come.

Thinking of Importing Material?There’s a legal and safe way to bring unique international plant material to Napa Valley. Foundation Plant Services (FPS) offers a quarantine, testing, and clean-up program for grapevine imports. It’s the only reliable way to ensure new material won’t introduce viruses or pests.
Learn more about legal grapevine importation

Our Collective Responsibility
We all have a role in protecting the long-term sustainability of Napa Valley agriculture. By sourcing clean material, staying informed, and collaborating with fellow growers, we can prevent future outbreaks, protect our land, and secure our industry for generations to come.