Fungus Problems

Fungus Diseases and Treatments

Pest Control

In this Series

Insect Problems
Fungus Problems
Beneficial Insects
Critter Problems
Azalea Problems
Invasive Plants
Houseplant Helper

This table lists the most common garden fungus diseases and methods for controlling them.

Organic/home remedies

Chemical

Mechanical

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Mildews and Molds

Disease

Organic Treatment

Chemical Treatment

Mechanical Treatment

Powdery Mildew on leaf

Scab on apples

Rose with Powdery Mildew

Botrytis on strawberries

Sulfur

When to Use: Apply to affected plants at the first sign of symptoms to prevent spread of disease to unaffected areas and new growth. Repeat treatments will likely be required if the fungus was left untreated too long.

Lime Sulfur or Wettable Sulfur

When to Use: As directed as trees leaf and bud in the spring.

Dormant oil and Lime Sulfur mix:

When to use: Use a horticultural oil in late winter or early spring before any growth starts. Apply as directed and spray until the mixture runs off.

Baking Soda Spray

Recipe: Mix one teaspoon of baking soda and one quart of water in a spray bottle. Add a few drops of dishwashing liquid. Adding 1/2 teaspoon of oil, such as Sunspray Dormant Oil, or even Canola oil may increase the effectiveness against black spot and other fungal diseases. Apply liberally.

Milk - yes MILK

Milk is effective against powdery mildews!

Recipe: 10-20% skim milk to water ratio. Milk seems to boost the plants immune system to fight off fungi. Apply liberally.

Non-systemic Fungicides

Anilazin
Bordeaux Mixture (copper sulfate and hydrated lime)
Captafol
Captan
Chlorothalonil
Copper Sulfate
Dichloran
Dinocap
Dodine
Ferbam
Folpet
Mancozeb
Maneb
Terrazole
Thiram
Zineb

Systemic Fungicides

Benomyl
Thiophanatemethyl

Avoid systemics on food plants. An exception can be made for long-season crops if used early in the season.

Fungi are reduced by growing plants in sunny locations with good air circulation and by reducing water contact on leaf surfaces.

Fungal diseases can be prevented by removing and destroying affected leaves that fall to the ground and by watering at the base rather than overhead.

On roses and other shrubs, remove leaves that form within about a foot of the ground, where splashing rain spreads disease. Consider planting disease-resistant varieties.

Rusts

Disease

Organic Treatment

Chemical Treatment

Mechanical Treatment

Rust on Leaves

As above.

Avoid systemics on food plants. An exception can be made for long-season crops if used early in the season.

When rust badly infects plants (particularly annuals), it cannot be eradicated. Dig up and destroy infected plants. Burning off affected crops is recommended where permissible under bylaws.

Damping Off

Disease

Organic Treatment

Chemical Treatment

Mechanical Treatment

Damping Off of seedlings

As above

As above.

Avoid systemics on food plants. An exception can be made for long-season crops if used early in the season.

To prevent damping off of seedlings started indoors, use only clean equipment and a sterile soiless potting mix. Before planting, water the flats. Sow seed sparingly. Sprinkle a thin layer of sand or perlite on the soil surface to keep stems dry at soil level. Remove the humidity-retaining cover as soon as germination starts. Mist lightly to maintain humidity. Use a fan to keep the air circulating around your seedling. Water the seedling from the base.

Fusarium and Verticillium Wilts

Disease

Organic Treatment

Chemical Treatment

Mechanical Treatment

Fusarium Wilt of tomato - note the dieback on one side

Typical V-shaped Verticillium wilt on tomato leaves.

Fusarium Wilt: healthy stem left, affected stem right

Lime Sulfur or Wettable Sulfur

When to Use: As directed as trees leaf and bud in the spring.

Dormant oil and Lime Sulfur mix:

When to use: Use a horticultural oil in late winter or early spring before any growth starts. Apply as directed and spray until the mixture runs off.

Milk - yes MILK

Milk is effective against powdery mildews!

Recipe: 10-20% skim milk to water ratio. Milk seems to boost the plants immune system to fight off fungi. Apply liberally.

Non-systemic Fungicides

Anilazin
Bordeaux Mixture (copper sulfate and hydrated lime)
Captafol
Captan
Chlorothalonil
Copper Sulfate
Dichloran
Dinocap
Dodine
Ferbam
Folpet
Mancozeb
Maneb
Terrazole
Thiram
Zineb

Systemic Fungicides

Benomyl
Thiophanatemethyl

Avoid systemics on food plants. An exception can be made for long-season crops if used early in the season.

Fusarium and Verticillium Wilt

Fusarium and Verticillium fungi are widespread and persist several years in soil. Rotate crops annually and avoid using any solanaceous crop (potato, tomato, pepper, eggplant) in the rotation 2 years in a row. If Verticillium wilt is a problem, also avoid the use of strawberries and raspberries, which are highly susceptible. Rotate with cereals and grasses wherever possible.

Remove and destroy infested plant material after harvest.

Maintain a high level of plant vigor with appropriate fertilization and irrigation, but do not over-irrigate, especially early in the season.

Plant disease-resistant tomato varieties, labeled V (for Verticillium) and F (for Fusarium). Grow heirloom varieties where available, which are genetically resistant to wilt.

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