ST. PAUL — Minnesota gardeners who grow basil for cooking should be aware of a new fungal disease that attacks the herb.

The Minnesota Department of Agriculture has confirmed the state’s first case of basil downy mildew.

The disease damages leaves, resulting in unmarketable plants. The fungus can affect basil grown in gardens as well as in commercial greenhouses.

A homeowner from Ramsey County contacted the agriculture department’s Arrest the Pest hotline with pictures of basil leaves that had dark, fuzzy growth. After the department confirmed it was basil downy mildew, the University of Minnesota confirmed a second case in Washington County.

The disease is spread by infected seed in transplants as well as by windblown spores.

Gardeners should plant only clean seed or transplants. The disease has no human health risk.