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Fungus Diseases and Treatments

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Houseplant Helper

Here is a list of most common garden fungus diseases and methods for controlling them.  Chemical, mechanical and "home remedy" treatments are covered.

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Mildews and Molds

DiseaseOrganic TreatmentChemical TreatmentMechanical Treatment

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Powdery Mildew on leaf

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Scab on apples

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Rose with Powdery Mildew

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Botrytis on strawberries


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

  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

Bordeaux Mixture (copper sulfate and hydrated lime)
Copper Sulfate

Systemic Fungicides


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.


DiseaseOrganic TreatmentChemical TreatmentMechanical Treatment

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Rust on Leaves

As above.
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

DiseaseOrganic TreatmentChemical TreatmentMechanical Treatment

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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

DiseaseOrganic TreatmentChemical TreatmentMechanical Treatment

Fusarium wilt of tomato.
Fusarium Wilt of tomato - note the dieback on one side

Verticillium wilt.
Typical V-shaped Verticillium wilt on tomato leaves.

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Fusarium Wilt: healthy stem left, affected stem right

As above.
As above.

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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