Elemental Sulfur
A naturally mined mineral fungicide and miticide effective against a wide range of fungal diseases including powdery mildew, rust, and black spot.
What it is
Elemental sulfur is a naturally occurring mineral that has been used as a fungicide for over 2,000 years. It is one of the oldest known pesticides and is fully approved for certified organic production. It is available as a wettable powder for spraying or as a dust for direct application.
What it does
Sulfur vapour and particles at the fungal cell surface interfere with electron transfer in fungal metabolism, disrupting spore germination and killing existing mycelium. It also has acaricidal properties, providing some control of spider mites. It works best as a preventive or at very early infection stages.
When to use
Begin applications before disease pressure arrives, particularly in humid or wet weather when fungal spores are active. For powdery mildew, apply at the first white patches. For rust and black spot, start preventive applications at bud break on susceptible plants. Repeat every 7 - 14 days through the risk period.
When not to use
Never apply sulfur when temperatures exceed 90°F as phytotoxicity is likely. Do not use within 2 weeks of applying horticultural oil as the combination can cause severe leaf burn. Avoid on sulfur-sensitive plants such as cucumbers, melons, and some apricot varieties. Check plant-specific tolerance before use.
How to apply
- 1
Mix wettable sulfur powder at the rate specified on the product label, typically 1/2-1 teaspoon per quart of water, and stir until fully suspended.
- 2
Check the air temperature forecast - do not apply if temperatures will exceed 86°F within 24 hours of spraying.
- 3
Spray all plant surfaces thoroughly in the morning, allowing foliage to dry before nightfall.
- 4
For dusting applications, apply a light, even coating over leaves using a dusting bellows in still, calm air.
- 5
Repeat every 7 - 14 days during the active disease season, or after each significant rainfall that washes off the deposit.
Garden, by Willowbottom recommends only organic, wildlife-friendly solutions. No synthetic pesticides, no harmful chemicals - ever.