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Elemental Sulfur

Sulfur disrupts the metabolic functioning of fungi and is one of the oldest known pesticides. Ancient Sumerians used sulfur compounds to kill insects and it may well be the earliest recorded use of insect pest control (Frazier, 1997).

Currently, sulfur is registered in the U.S. by EPA for use as an insecticide, fungicide, and rodenticide on several hundred food and feed crop, ornamental, turf and residential sites. It is also used as a fertilizer or soil amendment for reclaiming alkaline soils. Sulfur is applied in dust, granular or liquid form, and is an active ingredient in nearly 300 registered pesticide products. Sulfur is a non-systemic contact and protectant fungicide with secondary acaricidal activity.

Compatibility with other products is considered good. Numerous mixed products with insecticides and fungicides are manufactured. For reasons of phytotoxicity, mixing sulfur with oils should be avoided. Inert material is usually added during manufacture to prevent electrostatic "balling".

OMRI - May be used as a plant disease control or an insecticide (including acaricide or mite control) if the requirements of 205.206(e) are met, which requires the use of preventative, mechanical, physical, and other pest, weed, and disease management practices.

The Safer product shown to the left contains the OMRI™ (Organic Materials Review Institute) seal of approval.

Target Pathogens: Black spot, Rusts, Leaf Spots and Powdery Mildew

Target Pests: Spider Mites, Russet Mites, Broad Mites

Mode of Action: The mechanism of sulfur fungicide has been the subject of much research and speculation. In general, the elemental sulfur vapors have to come into direct contact with fungal spores and other tissues, preventing or inhibiting their germination or growth. Similar effects occur with certain mites and sucking insects, including larval stages of some thrips and scale insects.

"Plants have developed several defense mechanisms in response to stress and react to a certain pathogen attack through a combination of constitutive and inducible defense with S-containing compounds being involved compiled by Bloem et al. (2005). In principle plants have three major strategies to combat pathogens: cell wall strengthening, apoplastic defense for inhibition of microbial enzymes and poisoning of the pathogen by toxic compounds like phytoalexins (Huckelhoven, 2007)." Front Plant Sci. 2014

Application Tips: Read the label carefully of the brand and formulation you have selected. Apply the product according to the directions on the label. Since sulfur is abrasive to some metals, apply sprays with a plastic sprayer. Foliar injury may occur from applications made above 85 degrees F. DO NOT MIX SULFUR WITH HORTICULTURAL OIL SPRAYS. Sulfur is phytotoxic to most crops if applied two weeks before or after the application of a horticultural oil.

SULFUR IS NOT RECOMMEND TO BE USED PAST WEEK 3 OF FLOWERING.

Precautions and Safety Equipment: Minimize your exposure to pesticides.  Avoid contact with eyes.  Wear eye protection, long pants, a long-sleeved shirt, and a hat that can be washed after each use.  Always read label of individual product for additional directions.

Always check the label before purchasing or applying a pesticide product for a specific pest on a specific plant to be sure it can be applied. Follow label directions precisely.

Impact on Natural Enemies (provided by UC IPM):
Overall toxicity rating: Low To High
Specific impacts: Predatory mites (Low To High), parasitoids (High), general predators (Low To Moderate)
Impact on Honey Bees: Toxicity category: IV - Apply at any time with reasonable safety to bees

Selected References

University of California Statewide Integrated Pest Management

Pennsylvania Integrated Pest Management. A Short History of Pest Management. The field of Integrated Pest Management development. (Outline from M. Frazier; IPM in the Classroom 1997)

Missouri Botanical Garden

A Pesticide Information Project of Cooperative Extension Offices of Cornell University, Michigan State University, Oregon State University, and University of California at Davis.

Elemental sulphur as an induced antifungal substance in plant defence. Richard M. CooperJane S. Williams. Journal of Experimental Botany (2004)

Technical Note. SULFUR AS A FUNGICIDE. September 2008

Front Plant Sci. 2014; 5: 779. Milestones in plant sulfur research on sulfur-induced-resistance (SIR) in Europe. Elke Bloem, Silvia Haneklaus, and Ewald Schnug.

A PACIFIC NORTHWEST EXTENSION PUBLICATION • PNW649