Onion white rot is a potentially devastating disease of onions and closely related species, which can greatly decrease yields and reduce storage quality. It is spread primarily by movement of contaminated water, soil, equipment, tools, and machinery, and by infested onion plants and plant parts. Onion white rot disease is caused by the fungus Sclerotium cepivorum. Once a field is infested, the fungus remains indefinitely in the soil. The director finds that onion white rot disease is detrimental to the onion industry of Washington and establishes a quarantine to prevent introduction and spread of the disease into noninfested areas of the state.