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Powdery mildew in Monarda - maggiem - 07-06-2007

Hi everyone, I'm so disappointed this year about my Jacob Cline Monarda's. I planted them bare root last year and they did great, I had hummingbirds visiting them regulary. They came up again this year, but they have apparently developed a powder mildew disease and all the lower to middlw leaves have fallen off. They have flowers on them, but the plant looks unhealthy. How do I get rid of this without harming the hummingbirds? The plants have spread and I have considered just pulling them up in fall and starting over in fall or spring with fresh new plants (disease free). Thanks for any help. maggiem. Big Grin

Re: Powdery mildew in Monarda - doretta - 07-06-2007

I would just cut them down and toss them far far away. The hummingbirds will be mad but the flowers will grow back in a short while.

Re: Powdery mildew in Monarda - IntrepidMeredith - 07-06-2007

Powdery mildew can be a problem for monarda. It's caused by a combination of too much water and not enough air circulation. Try thinning the plants to increase air circulation, and water the plants only at soil level, not from above. I think there's some kind of spray you can make with baking soda and water that will help kill the mildew, but I'm not sure of the ratios to use, and it may be more of a preventative measure rather than something to use once the mildew has already taken hold. Also, the monarda will self seed like crazy, so even if you get rid of this year's plants, you should still have plenty again next year.

Re: Powdery mildew in Monarda - maggiem - 07-06-2007

Thanks for the suggestions, I did read about a solution made from baking soda and I tried it, the leaves kept falling. I have been thinning them gradually when the weakened stems start falling over. Today I tried another solution, (you might get a laugh at this one) made from milk and water. I read about it after doing a google search. And I love watching the hummingbirds, so I really can't bear to cut them back yet. It is already July, I'm not sure they would have time to grow back. I just wonder, though, if when I cut them back in the fall, will that get rid of the powder mildew. The stems seem affected, too, kind of black looking. I'll definitely either have to do some major thinning or just pull them up and replace them, eventually. Thanks, maggiem.

Re: Powdery mildew in Monarda - KimmSr - 12-21-2007

All Monarda's are susceptible to Powdery Mildew, some cultivars are a bit more resistant but they still get it. PM develops on plants after the weather has been hot and dry and turns somewhat cooler and a bit damper, which is why many people think it is related to watering, which it is not.
Once a plant has PM the affected leaves can fall off bit not always and not on all plants (Lilacs do not loose their leaves) and on some plants the PM can grow thick enough to stop photosynthesis so the plant drops that leaf. A mixture of 1 teaspoon of baking soda (Cornell says that Potassium Bicarninate works better and it does bit that is not as readily available) in 1 quart of water and sprayed every 5 to 7 days once PM is noticed can help control it and if the mixture is sprayed on susceptible plants every 7 to 10 days before infection occurs that can help prevent PM from taking hold.