Powdery Mildew on Bergamot (Monarda)
Answered by: Conrad Richter
Question from: Cynthia Van Hazinga
Posted on: October 18, 2003

I am writing a short piece for Garden and Deck Design, a Woman’s Day SIP. We need to help a reader who had a problem with powdery mildew on her monarda. What should we suggest?

Monardas are notorious for their susceptibility to powdery mildew. The wild species Monarda fistulosa is probably among the most susceptible. Many of the traditional cultivars such as ‘Blue Stocking’ and ‘Violet Queen’ can develop heavy mildew infestations also.

Typically powdery mildew strikes during the dry warm summer months. Mildew can cause stunting, die back and even death in severe cases.

In regions where monardas are regularly striken with mildew the best defense is to plant tolerant or resistant varieties. A spray made of soap and baking soda may help; this treatment works well on powdery mildew on cucumbers and melons, for example, but I have not tried it on monarda.

Also, which varieties are less inclined to mildew? Is ‘Jacob Cline’ a good one?

I am not familiar with ‘Jacob Cline’, but among the varieties we sell, ‘Marshall’s Delight’, ‘Petite Delight’ and ‘Petite Wonder’ are mildew resistant. The wild species, M. citrodora (lemon bergamot), seems to be mildew-resistant also.

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