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Stow Agricultural Commission

Stow, Massachusetts

Right-to-farm Bylaw
Property Notification

Basil Downy Mildew

Growers throughout the Northeast need to be on the lookout for a downy mildew of basil, a disease that is relatively new to this region. This disease has the potential to cause serious losses in basil throughout New England. Symptoms of the disease start with diffuse yellowing of the leaves, giving the appearance of nutritional deficiency. At a later time, black spores are formed on the underside of the leaves giving the appearance of dirt splashed up from below. Necrosis of the leaf follows.

This disease has already destroyed basil crops on several local farms. See for details.

Update 2015: Basil Downy Mildew does not overwinter in this area, but it does blow up from southern areas to arrive here in mid to late summer. The arrival date will vary from year to year, but it will eventually arrive. Once in the area it will spread readily to adjacent areas. Basil grown indoors may be protected for a while, since the disease forms on leaves that are exposed to moisture and are accessible to spores brought by winds.

We can expect basil to succumb almost every year. The timing is uncertain, but in 2014 the disease struck early. If you grow basil for pesto, make as much pesto as you can early in the season.

last update 2015 December 18