Hypothesis: treating powdery mildew with ozone generator

I have a hypothesis that within an indoor or greenhouse setting it may be effective, efficient, and less toxic to treat powdery mildew using an ozone generator.

Chads Midgly, a well-known greenhouse and indoor gardener in Utah who grows produce to sell it in farmers markets, has had a lot of painful experience treating powdery mildew, especially on large tomato crops he grows in a house (a basement, I think). He detailed the treatments he's tried at https://tinyurl.com/7prerszw and asked his followers if they'd tried other treatments with better success. He currently uses a “Clear Light” UVC lamp with mixed success.

I had a hunch that ozone, as a gas that is heavier than oxygen or carbon dioxide -- a gas used to kill odors in homes and automobiles by killing bacteria that causes the odors -- might treat more of the surface areas of a plant and its surrounding soil and compost than other treatments people use like dust, spray, or light. So I asked Grok some questions, and this is the product of our interaction:

My last of a series of questions to Grok:

I have an acquaintance who has lost whole crops of indoor tomatoes to powdery mildew, has tried many treatments and learned how to control it but not completely kill it off in a very efficient way. Today he asked his Facebook followers what they'd tried to solve it. He grows hundreds or thousands of tomato plants on culinary shelves in a basement. Armed with my hypothesis and the info you gave me, I've recommended that he experiment with an ozone generator on a few of his shelved tomato plants after sealing the shelves in sheet plastic.

Grok's answer

Your acquaintance’s situation sounds like a perfect case for testing the ozone generator idea, especially since he’s already battled powdery mildew with mixed success. Losing whole crops is brutal, and if he’s growing hundreds or thousands of tomato plants on culinary shelves in a basement, efficiency is key. Your recommendation to experiment on a few sealed shelves is spot-on—small-scale testing keeps the risk low while gauging if ozone can be his silver bullet. Here’s how I’d frame it for him, based on what we’ve discussed, plus a few tweaks for his setup:

The Pitch

“Hey, I’ve been digging into powdery mildew solutions, and ozone generators might be worth a shot for your basement tomato shelves. Ozone’s a strong oxidizer—it can kill mildew spores and active growth by messing up their cells. Since you’ve got shelves, you could seal a few with sheet plastic to trap the ozone, run a small generator for a short burst, and see if it knocks out the mildew without hurting the plants. It’s not about displacing CO₂ or anything fancy—just pure oxidative firepower. Here’s a simple plan to try it.”

Suggested Experiment

Pick a Test Shelf: Start with one or two shelves of infected plants—small enough to manage but enough to see real results.
Seal It Up: Wrap the shelf in sheet plastic (like painter’s drop sheets). It doesn’t need to be airtight—ozone will still build up if the leaks are minimal. Tape or clip the edges to keep it snug.
Ozone Generator: Grab a cheap, portable one (tons online, like the kind for car or room purification—200-500 mg/h output should do for a shelf). Place it inside the plastic or rig a tube to pump ozone in.
Run It: Try 20-30 minutes at first, aiming for 1-2 ppm ozone (if he’s got a meter; if not, just go by the generator’s output specs and keep it moderate). Short bursts minimize plant stress.
Ventilate: After, peel back the plastic and air out the basement (open a window, run a fan). Ozone breaks down fast, so it won’t linger long.
Check Results: Watch the plants over a few days—look for mildew fading (white spots shrinking or browning) and any leaf damage (yellowing or spotting).

Why It Might Work

Basement Bonus: Low natural airflow down there means ozone can concentrate where it’s needed, unlike a breezy greenhouse.
Shelf Scale: Small, enclosed shelves are easier to treat than a whole room—less ozone needed, less hassle.
Mildew Weakness: Powdery mildew hates oxidative stress, and ozone’s proven effective in ag settings for similar fungi.

Watch Outs

Tomato Tolerance: Too much ozone (say, >0.2 ppm for hours) might burn the leaves. If the plants look sad post-treatment, dial back time or output next round.
Safety: Tell him to stay out of the basement during and right after—he doesn’t want to breathe this stuff (it’s like chlorine for your lungs).
Repeat Attacks: Ozone kills what’s there, but if spores keep floating in from untreated plants or bad humidity, it’s not a one-and-done fix. He might need to hit it periodically or tweak his setup (better air circulation, lower humidity).

Selling the Experiment

Since he’s already tried “many treatments” and only learned to control—not kill—the mildew, ozone’s a fresh angle. It’s not some systemic fungicide that lingers in the plant (which might worry a culinary grower) or a labor-intensive spray. If it works on a few shelves, he could scale up, maybe rigging a generator to treat multiple units with timers or tubes. Worst case, he’s out a couple bucks on a generator and some plastic, but best case, he saves his crop.