Sulfur

Tier B — Program Tool Caution Mineral OMRI Listed

Quick Facts

Type
Mineral
Source
Elemental sulfur, one of the oldest pesticides in human history
OMRI Listed
Yes ✓
Bee Safe
Yes
Pet Safe
Yes
Residual
7-14 days; not systemic
Best For
Spider mite control combined with fungal disease prevention. Cool-weather applications.

What Is Sulfur?

Disrupts cellular respiration in mites and fungi by interfering with electron transport. Also works as a repellent — mites avoid sulfur-treated surfaces. Primarily valued as a fungicide but has significant acaricidal (mite-killing) properties.

Source: Elemental sulfur, one of the oldest pesticides in human history

What Pests Does Sulfur Kill?

Sulfur is effective against the following pests:

Spider Mites Thrips Mealybugs

How to Apply Sulfur

Best for: Spider mite control combined with fungal disease prevention. Cool-weather applications.

Avoid for: Hot weather (above 85°F), cucurbits, within 30 days of any oil application.

Residual activity: 7-14 days; not systemic

Safety Profile

CategoryRating
Bee Safety 🟢 Safe for bees
Pet Safety 🟢 Safe for pets
Overall Rating Caution — Use with caution — timing and technique matter

Why Isn't Sulfur Working?

If Sulfur isn't delivering results, check these common failure modes:

Temperature sensitivity — phytotoxic above 85°F; never apply in heat

Oil incompatibility — never apply within 30 days of horticultural oil

Burns tender growth on some varieties (cucurbits especially sensitive)

Acidifies soil over time with repeated use

Best Sulfur Products

Bonide Sulfur Fungicide

Dust/Spray

Micronized sulfur for gardens

Hi-Yield Wettable Dusting Sulfur

Wettable powder

Versatile — dust or spray application

Sources and Further Reading

Related Ingredients

Beauveria bassiana

Tier B

Beauveria bassiana is an entomopathogenic fungus that penetrates insect exoskeletons and colonizes the body from within, killing the host in 3-7 days. Most effective in humid conditions like greenhouses, it provides long-term biological suppression of whiteflies and thrips.

Metarhizium anisopliae (Green Muscardine)

Tier B

Metarhizium anisopliae (green muscardine fungus) infects soil-dwelling insects and ticks through cuticle penetration, producing destruxin toxins that kill the host in 5-14 days. Dead insects sporulate green, spreading the fungus to nearby pests.

Kaolin Clay (Surround)

Tier B

Kaolin clay creates a white particle film on plant surfaces that irritates insects, blocks egg-laying, and makes plants unrecognizable to pests. It does not kill — it creates a physical barrier that deters beetles, moths, and aphids before they establish.