How to Prevent and Treat Fungal Diseases on Your Market Farm
By Jonathan Dysinger and John Dysinger
Updated on
Show Transcript
0:00Hi guys. In this video, we're going to be talking about common fungal diseases and how to counteract them. So, Dad,
0:06what's your advice for dealing with fungal diseases?
0:10Well, there's cultural things you can do and then of course there's sprays and things you can use. So, I think start with the cultural things.
0:22Um, I can't overemphasize enough the importance of healthy plants.
0:28I've seen over and over um plants that are really really healthy are less susceptible to diseases.
0:38So just really being on top of your game when it comes to to soil health um I think is the place to start.
0:51And then from there um you know fungal diseases for the most part it's all about moisture and too much moisture.
1:02So um if you're having issues and tomatoes of course are the the classic
1:09example of a plant that does not do well with moisture on the leaves.
1:15And so I would highly recommend using drip irrigation with your tomatoes.
1:21Uh so that's a simple cultural practice but keeping as much moisture off the leaves as possible.
1:30Um so drip versus overhead irrigation but also plant spacing.
1:37If you get plants spaced too tightly then there's not enough air flow and you
1:45have more issues with with fungal disease. So, space the plants out a little more. With soil blocks, you can
1:53do things in the winter like not planting the soil block, but just putting it on the surface.
2:00And um that gives a little more airflow around the base of the plant.
2:07And and then sunlight of course is another thing. Sunlight is one of the best uh antifungal
2:16um medicines, whatever you want to call it. So,
2:23just making sure that the plants are getting good airflow and good sunlight. Yeah. you know, with with trees,
2:33you know, fruing tree fruiting crops um or fruing tree crops,
2:42they often take out prune out the center of the plant just to get more sunlight and air in there. So
2:50in the vegetable garden, just be thinking of the same kind of things,
2:55just making sure that you're growing things in a way Mhm. So then as far as uh sprays or some
3:05sort of uh Yeah. If if it does get a little out of hand at times, like what are techniques? What's your first go-to
3:13technique for handling it with a with a spray or some sort of treatment?
3:18Well, you know, there's a lot of different fungal diseases and there's a lot of different sprays
3:25and obviously we're we're coming from an organic perspective where we're not wanting to spray a lot of stuff that they use for fungicides.
3:37Um, so you have some that are just killing the fungus and things like SanDate,
3:49which which is a hydrogen, what is it?
3:52Hydrogen dioxide or something that actually
3:59explodes the cells of the fungus or whatever. I don't know exactly how it works. So you have those which can be
4:07effective and then you have other ones which are kind of um good guys out competing bad
4:16guys kind of sprays where you're spraying beneficial
4:22organisms on the plants to out compete the disease organisms.
4:31Interesting. So you're you want to look at mode of action um and
4:39something that as is as disease specific as possible kind of with insecticides.
4:46You want to make sure you're not just nuking everything. Yeah. You know. So then if if you notice a crop appears to
4:54be having some sort of fungal issues um or has you know has been diseased how do you identify what kind of fungal disease it has?
5:05Well, there are books and you know websites where you can take, you know,
5:11look at pictures and I mean the bottom line is a lot of these diseases are such
5:18that the only way you're going to know positively is to send it to the A
5:25extension service kind of thing and have have them tested.
5:31But I guess I don't worry so much about the specific disease as just
5:40um focusing on keeping the plants healthy.
5:44Um although there are some diseases that you know especially with strawberries that you really want to avoid and in
5:53some cases pulling out infected plants is a good practice. Pull them out and get them far away.
6:00Yeah. Get them out of the field cuz you know fungus spreads through spores and
6:07so you don't want that happening in your field. Yeah. So I don't know that's kind of general but that's all we have time for.
6:17Yeah. Yeah. Well if if you want to try Sanidate uh it's available at Farmer's Friend. A little behind the behind the
6:25scenes there. we have to get a a hazardous shipping uh license or training to do that. And it was it's
6:32been quite a process uh going through thinking we have it figured out and starting to ship it and having issues and having to get stuff back and all
6:39this rigomearo. But we're finally uh shipping sanitate um and it's it's arriving at its
6:46intended destination. So that's good. Uh so yeah, come buy some sanitate from Farmer's Friend and if you have fungal
6:53issues that you need to spray, we can definitely provide that. Um hope this information was helpful and if you have any questions, drop them in the comment
7:02section down below and we might answer those questions in a future video. Until next time, happy growing.
7:09[Music]
The best defense against fungal diseases on a market farm starts with cultural practices, not sprays: build healthy soil, use drip irrigation instead of overhead watering, space plants for good airflow, and maximize sunlight exposure. When you do need to intervene, choose organic-approved products like SaniDate (hydrogen peroxide-based) or beneficial organism sprays that outcompete disease — and always consider the mode of action so you're targeting the problem without nuking everything.
Fungal diseases are one of the most common — and most frustrating — challenges on a market farm. They can take down a healthy-looking tomato crop in a matter of days, ruin a strawberry patch, or quietly reduce yields across your entire operation.
The good news is that most fungal problems are preventable with the right cultural practices. And when prevention isn't enough, there are effective organic options that won't compromise the integrity of what you're growing.
My dad, John Dysinger, has been dealing with fungal pressure at Bountiful Blessings Farm for 27 years. In a recent video, we talked through his approach — starting with the cultural practices that prevent most issues, and then the organic treatment options for when things get out of hand.
What Causes Fungal Diseases in Vegetable Crops?
Almost all fungal diseases come down to one thing: too much moisture. Specifically, moisture sitting on plant leaves and stems for extended periods creates the perfect environment for fungal spores to germinate and spread.
But moisture alone isn't the whole story. My dad has seen over and over that plants growing in truly healthy soil are significantly less susceptible to disease. A stressed plant in depleted soil is far more likely to succumb to fungal pressure than a vigorous plant with a strong root system and good nutrition.
So the starting point for fungal disease management isn't a spray bottle — it's your soil health program.
How Do You Prevent Fungal Diseases? (Cultural Practices)
The most effective tools against fungal disease are the ones you implement before any symptoms appear. My dad considers these non-negotiable on his farm.
Use Drip Irrigation Instead of Overhead
This is the single simplest cultural change you can make, especially for disease-prone crops like tomatoes. Overhead irrigation — sprinklers, impact heads, anything that wets the foliage — creates exactly the conditions fungal diseases need to thrive.
Drip irrigation delivers water directly to the root zone and keeps the leaves dry. Tomatoes in particular do not do well with moisture on their leaves, and switching to drip can eliminate a huge portion of your fungal pressure with no sprays required.
Space Your Plants for Airflow
When plants are spaced too tightly, air can't circulate between them. That trapped, humid air around the foliage is a breeding ground for fungal spores.
It's tempting to pack plants in tight to maximize bed space — especially when you're trying to make every square foot count. But if you're dealing with recurring fungal issues, giving your plants a little more breathing room can make a significant difference.
My dad also uses a technique with soil blocks in winter: instead of pressing the block down into the soil, he places it on the surface. This creates a small air gap around the base of the plant that improves airflow right where moisture tends to accumulate.
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Maximize Sunlight Exposure
Sunlight is one of the best natural antifungals there is. Making sure your crops are getting full sun exposure — and not shaded by overgrown neighboring plants, tunnel walls, or poor row orientation — helps keep foliage dry and hostile to fungal growth.
My dad draws a parallel to fruit tree management: orchardists routinely prune out the center of the tree to get more sunlight and air into the canopy. The same principle applies in the vegetable garden. Think about how you're positioning and managing your plants to keep light and air moving through the canopy.
Start with Healthy Soil
This one bears repeating because it's the foundation everything else builds on. My dad can't overemphasize how much difference healthy soil makes. Plants growing in biologically active, nutrient-rich soil develop stronger immune responses and are simply less vulnerable to fungal attack.
If you're dealing with chronic fungal pressure across your farm, the answer might not be a better spray — it might be a better soil-building program. Cover crops, compost, and good rotation all contribute to the kind of plant vigor that resists disease naturally.
What Organic Sprays Work Against Fungal Diseases?
When cultural practices aren't enough and disease pressure is building, there are organic-approved options. My dad approaches these with two key principles: use products that are as disease-specific as possible, and understand the mode of action so you're not just nuking everything in the field.
Direct-Kill Products
Products like SaniDate 5.0 use hydrogen peroxide and peroxyacetic acid to directly destroy fungal cells on contact. SaniDate is OMRI-listed and approved for organic production. It's effective as both a foliar spray for active fungal issues and as a post-harvest sanitizer for your processing area and tools.
Beneficial Organism Sprays
The other approach is biological — spraying beneficial microorganisms onto your plants that outcompete the disease organisms for space and resources. Instead of killing the fungus directly, you're populating the leaf surface with "good guys" that crowd out the "bad guys."
This is a more nuanced strategy, but it aligns well with the regenerative approach most market farmers are already taking with their soil. You're working with biology rather than against it.
Know the Mode of Action
Whatever you use, my dad recommends understanding how it works. Some products kill directly. Some outcompete. Some do both. Just like with insecticides, you want to be targeted in your approach — a broad-spectrum nuke might solve your immediate problem but can also wipe out beneficial organisms that were helping keep things in balance.
How Do You Identify Fungal Diseases?
Honestly? It's not always easy.
There are books and websites with photo guides that can help you narrow down what you're dealing with. But my dad's honest assessment is that many fungal diseases look similar enough that the only way to get a definitive identification is to send a sample to your local agricultural extension service for testing.
That said, my dad doesn't worry as much about identifying the specific disease as he does about keeping his plants healthy in the first place. A strong plant in healthy soil with good airflow and dry foliage is going to resist most fungal pressure regardless of the specific pathogen.
The exception is certain crops — strawberries in particular — where specific diseases can be devastating and fast-spreading. In those cases, the best practice is to pull infected plants immediately and get them far away from the field. Fungal diseases spread through spores, and leaving an infected plant in the row is an invitation for the disease to move through the rest of your crop.
The Takeaway
Fungal disease management on a market farm is mostly about prevention. Healthy soil, drip irrigation, good plant spacing, and plenty of sunlight will prevent the majority of issues before they start.
When you do need to intervene, reach for targeted, organic-approved options like SaniDate 5.0 or beneficial organism sprays. And if a plant is clearly infected — especially in crops like strawberries — pull it and get it out of the field before the spores spread.
The best fungicide is a healthy plant in healthy soil. Everything else is backup.
Frequently Asked Questions
Excess moisture on plant foliage is the primary driver of most fungal diseases. When leaves stay wet for extended periods — from overhead irrigation, poor airflow, or humid conditions — fungal spores germinate and spread rapidly. Combining moisture management with healthy soil and good plant nutrition is the most effective prevention strategy.
Switch from overhead to drip irrigation to keep moisture off the foliage, space plants generously for airflow, and make sure they're getting full sunlight. Tomatoes are especially susceptible to fungal disease when their leaves stay wet. Growing in tunnels with drip irrigation eliminates most tomato fungal issues.
SaniDate 5.0 is a hydrogen peroxide and peroxyacetic acid-based sanitizer that destroys fungal cells on contact. It's OMRI-listed and compliant with NOP organic standards. It can be used as a foliar spray for disease control, a post-harvest produce wash, and a surface disinfectant for greenhouse equipment.
Drip irrigation is strongly preferred for disease-prone crops. It delivers water directly to the root zone without wetting the foliage, removing the moisture conditions that fungal diseases need to establish. This one change can dramatically reduce fungal pressure, especially on crops like tomatoes.
Photo guides in books and online resources can help narrow it down, but many fungal diseases look similar. For a definitive identification, send a sample to your local agricultural extension service for testing. In practice, focusing on strong cultural prevention — healthy soil, dry foliage, good airflow — protects against most fungal pathogens regardless of the specific disease.
In many cases, yes — especially with crops like strawberries where specific diseases spread quickly through spores. Pull infected plants and remove them from the field entirely. Leaving diseased plants in the row allows spores to spread to neighboring healthy plants and can turn a small problem into a field-wide outbreak.
Healthy, biologically active soil grows more vigorous plants with stronger natural defenses against disease. While good soil won't make your crops immune, it significantly reduces their susceptibility. If you're dealing with chronic fungal pressure across your farm, improving your soil health program is often more effective than finding a better spray.
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