You've spotted something off on your vegetables, maybe a white powder on the squash leaves or a wilted tomato plant that won't perk back up, and you're trying to figure out what it is. There are a fair number of fungal diseases that hit vegetables, they show up at different points in the season, and most of them trace back to one thing: weird weather. This page walks through the fungal diseases most likely to show up in a home vegetable garden, and the fungicide program that prevents nearly all of them.
In short:
• Nine fungal diseases account for most of the problems vegetable gardeners see, from downy mildew to fusarium wilt.
• Once a fungal disease strikes, you can't cure it — the real job is preventing it before it starts.
• One biological fungicide, Actinovate, applied on a schedule prevents most of them at once, above and below the soil.
• Each disease has its own timing and vegetable preferences, so knowing what you're looking at helps you catch it earlier next season.
As you can see with this list there are a fair number of fungal diseases that can strike various vegetables in the garden. They will hit at different times in the season. Very often they are caused by weird weather; cold and wet or hot and wet, etc.
We say don’t worry about identifying each fungal disease. It’s not worth the effort and you really don’t need to. Usually once a fungal disease strikes there is nothing you can do to “cure” it.
The main job is to “prevent” all fungal diseases from attacking any of your vegetables. You can now do that with just one product and that is ACTINOVATE, a relatively new biological fungicide that is very effective in preventing most fungal diseases above and below the soil surface.
The Fungal Disease Prevention Program For Vegetables
Here is the fungal disease prevention program for all your vegetables:
- Every time you plant a vegetable seedling you include some Actinovate in the hole
- Then when a vegetable seedling gets to be 5 or 6 inches tall you begin a monthly spray program with Actinovate right to first frost.
- IMPORTANT – If any vegetable in your garden had any fungal disease problem last year, then for that vegetable this year you spray Actinovate every two weeks from planting to harvest.
If you follow this program your vegetables should seldom suffer from any of the following fungal diseases.
Downy Mildew
Pods are mottled with white, fuzzy fungus strands on them. Pale Areas on Upper Leaves yellowing leaves with a greyish or white mold on their underside. Older leaves have tiny black fungi spots on their leaves, and slowly die in the autumn.
Downy mildew shows up most on peas, beans, and cucumbers, and it spreads fastest during cool, wet spells in spring and fall. Check the underside of leaves after a rainy week — that fuzzy gray-white coating is the first place it appears, days before the tops of the leaves show any damage.
Powdery Mildew
Leaves coated with white powder. Powdery mildew is the fungal disease vegetable gardeners run into the most, especially on squash, cucumbers, and zucchini in the middle of summer. It likes dry days and humid nights, and unlike most fungal diseases it doesn't need wet leaves to spread, so it can show up even in a dry summer.
Anthracnose
Fruits develop small, round, water-soaked spots; later, fruits darken and rot . Water-soaked Spots On Pods, Stems can occur on beans, as well as vegetables like brassicas, cucumbers, peppers, and tomatoes, creating sunken brownish spots. Remove and dispose of infected plants. Buy disease-resistant seed varieties.
Anthracnose usually shows up once fruit starts to ripen, not on young green fruit, and it spreads fastest when it rains right before harvest. Tomatoes and peppers are the two vegetables it hits hardest in most home gardens.
Rust
Orange-tinged Spots Under Leaves. Rust is most common on beans and asparagus, and it spreads through tiny spores that wind carries from plant to plant, so a rust problem on one bean row can jump to the next row within days if the weather stays humid.
Blights
They thrive in warm, wet weather and may affect vegetable crops such as potatoes and tomatoes. There are two kinds worth knowing apart: early blight shows up as dark rings on the lower, older leaves first, while late blight moves faster and can blacken an entire tomato or potato plant within a week during a cool, rainy stretch.
Botrytis (grey mold)
Is a common vegetable disease that affects plants such as lettuces and tomatoes. Botrytis takes hold fastest on plants that are crowded together with poor airflow, and it usually starts on a dead flower petal or damaged leaf before spreading to healthy tissue nearby, so cleaning up spent blooms and trimmings goes a long way toward keeping it out.
Clubroot
Is a fungal disease that attacks brassicas such as broccoli, cauliflower, and cabbage. Clubroot lives in the soil for years once it shows up, so the swollen, misshapen roots it causes are a sign to rotate brassicas out of that bed for several years rather than replanting broccoli or cabbage there again right away.
Damping off
Is a fungal disease that can affect any type of vegetable plant, Damping off strikes right after seeds sprout, when the stem is still thin and soft. A seedling that was fine the day before and is suddenly toppled over at the soil line, with a thin, dark, pinched stem, is almost always damping off, not something you did wrong with watering.
Fusarium wilt and verticillium wilt
Are fungal diseases that cause leaves to turn yellow and look wilted. The yellow leaves turn brown and the disease usually starts from the bottom of the plant and works its way up, eventually killing the plant.
Tomatoes are the vegetable most home gardeners see these two wilts on, and once the yellowing starts on the lower leaves, there's no fungicide that reverses it — the only real fix is planting fusarium- and verticillium-resistant tomato varieties (look for a V and F on the plant tag) next season.
Common Questions About Fungicide For Vegetables
Which fungicide is best for vegetables?
For most home vegetable gardens, a single preventive fungicide covers the widest range of problems. Actinovate is a biological fungicide that works above and below the soil line, so it's the one product recommended here to prevent fungal disease across your whole vegetable garden rather than buying something different for each disease.
Can I spray fungicide on vegetables?
Yes — most vegetable fungicides, including Actinovate, are labeled safe for use right up to harvest when you follow the directions on the label. The key is spraying to prevent disease before it starts, since fungal diseases can't be cured once they take hold.
When should you spray fungicide on vegetables?
Start when you plant your seedlings, working some fungicide into the planting hole, then spray monthly once the seedling reaches 5 to 6 inches tall and keep going until the first frost. If a vegetable had a fungal problem the year before, spray that vegetable every two weeks instead of monthly, from planting all the way to harvest.
What causes fungus on vegetable plants?
Fungal spores are already present in most gardens, and they take hold when the weather gives them the right conditions, usually a stretch of cold and wet or hot and wet weather. That's why fungal disease often strikes in waves tied to the weather rather than showing up the same way every year.
What are the symptoms of damping-off in vegetable seedlings?
A seedling that suddenly topples over at the soil line, with a thin, dark, pinched stem, is showing classic damping-off symptoms. It strikes right after seeds sprout and moves fast, so a seedling that looked healthy the day before can be down within 24 hours.
Conclusion
Most fungal diseases on vegetables trace back to the same handful of culprits, and none of them can be cured once they've taken hold — the whole game is preventing them. Sticking to one fungicide program from planting through frost, and knowing which disease favors which vegetable and which weather, is what keeps a garden ahead of the problem instead of reacting to it after the damage is already done.
