OM DENNE EPISODE
In this conversation, Fritz continues his deep dive with Thijs Verschuuren of Herman J. Wiemer, exploring practical baby steps toward biodynamic and organic vineyard management. Thijs walks through how he structures a non-systemic spray program in a high-disease-pressure region, breaking down critical spray timing, coverage strategies, and why he treats bloom and cap fall as "non-negotiable" spray windows.
They discuss how Thijs combines copper, sulfur, plant teas, biologicals, and newer tools like chitosan-based fungicides and kaolin clay to target downy mildew, black rot, powdery mildew, and leafhoppers, while staying within strict copper limits and managing livestock safety.
Fritz and Thijs also cover biodynamic teas, how forecasting and 48‑hour brews fit into a preventive program, and why daily scouting and mapping disease "pockets" are essential. The conversation concludes with canopy management, pruning, mechanization, and thoughtful leaf removal that maintain disease control without sacrificing the acidity and fruit quality of Riesling and Chardonnay on the path to Demeter certification.
In this episode, you will hear:
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Why spray timing and coverage matter more than product choice in organic and biodynamic programs
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How to integrate copper, sulfur, oils, chitosan, and kaolin clay while respecting label limits and site conditions
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Practical strategies for managing downy mildew, black rot, and powdery mildew with a mostly protectant toolbox
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How biodynamic teas and preparations fit into a preventive, weather‑driven vineyard health program
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Daily scouting, mapping, and localized spraying as core tools to limit disease spread and input use
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Today's Guest:
Thijs Verschuuren is the Director of Vineyard Biology & Biodynamic Specialist at Hermann J. Wiemer Vineyard in upstate New York.
Connect with Thijs at https://www.wiemer.com/ or follow him at hermannjwiemer.
Resources:
Come grow with Fritz at https://www.virtualviticultureacademy.com! Save $75 off your first year of membership with the code Underground at checkout.
Have a vineyard question? Go to VineyardUndergroundPodcast.com and click the Ask Fritz button.
Episode Sponsor:
Today's episode was brought to you by Clemens and HydroGeo Environmental.
Thank you to Clemens Technologies for sponsoring today's episode. Clemens Technologies is the market leader in machinery for all elements of vineyard management. Visit https://www.clemens-online.com/us/ and provide the code UNDERGROUND to receive 5% off your order of in-stock machinery. Or reach out to Thomas Clemens directly at thomas@clemens-america.com with any questions.
Thank you to HydroGeo Environmental for sponsoring today's episode. For over 20 years, Bubba Beasley and his team have helped vineyard growers with site assessments, mapping, soil and groundwater evaluations, and optimal vineyard layouts. Using the latest technology and industry expertise, HydroGeo brings clarity to even the most complex landscapes. Visit HydroGeoEnvironmental.com and mention the Vineyard Underground podcast for a special discount on your service.
Episode Credits
If you like this podcast and are thinking of creating your own, consider talking to my producer, Emerald City Productions. They helped me grow and produce the podcast you are listening to right now. Find out more at https://emeraldcitypro.com. Let them know we sent you.
