Downy mildew, techniques and organic treatments to avoid it

Famous for being vineyard owners’ #1 enemy, downy mildew is a constant threat to grape harvests. This blight also threatens certain other vegetables from the vegetable patch such as tomatoes and potatoes, too.

Regularly applied preventive treatment should help you produce a beautiful harvest without any trace of downy mildew.

How to recognize downy mildew

Symptoms of downy mildew start with the appearance of several spots on the leaves that encroach on neighboring leaves.

  • This is a fungal disease that mainly impacts grapes, tomatoes and potatoes.
  • Brownish spots appear on and under the leaves, and spread until the leaves turn completely brown and fall off.

Conditions in which downy mildew appears and spreads

Downy mildew particularly likes warm and moist settings, as well as dense foliage that keeps air and light away.

  • Moisture is the main factor that triggers its spread.
  • Like most fungal attacks, downy mildew will spread fastest after rain showers.
  • Mildew is hindered when plants are spread far apart and air circulates well.

Organic downy mildew treatments

It’s possible to use very effective organic downy mildew treatments.

  • Bordeaux mixture is the only effective preventive treatment against downy mildew.
  • Apply regularly at the beginning of spring and in fall.
  • Treat during the entire vegetative phase.
  • Treat regularly, on average every two weeks and after every rainfall.
  • In the case that downy mildew appears, only a curative treatment will have any effect.

Downy mildew and baking soda

Baking soda is an excellent solution to treat downy mildew.

  • Dissolve 1 table spoon baking soda in 1 quart (1 liter) water (ideally rainwater or mineral water, for the water to be softer).
  • In dry weather, spray this mix on all the leaves, spraying both on top and on the underside of leaves.

Other diseases and treatments