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Gardening in the UK

Mildew on michaelmas daisies

alison_froglady

19 years ago

I have what appears to be mildew on my michaelmas daisies. They start off with beautiful new leaves which then get the mildew leaving the leaves to finally go brown and die off. They are about a foot high now and a good 8 inches is now all dead old leaves. I have 2 of these plants in pots in my back garden and 1 in a pot in the front garden which is much sunnier. The back garden is very shady and cooler. The plant in the front garden is perfectly healthy but hasn't grown as fast or as tall as the 2 in the back garden yet they both have the problem.

What can I do about this? I don't know anything about mildew and I suppose I am just assuming that this is the problem. Can I just wipe the leaves off or will it stay on them. I just thought that the leaves would stay as they were. I didn't expect them to die off.

Can anyone help me here Thankyou.

Alison

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Comments (3)

shrubs_n_bulbs
19 years ago
They are renowned for it. One approach is to look for resistant varieties. I think A. novi-belgii is the one to avoid, hope I didn't get that backwards.

Mildews are moulds that are specific to a particular plant. The spores germinate when the leaves are dry but the air is still and humid. Good ventilation is important for preventing mildew, but also keeping the roots moist. Mildew spores do not germinate, in fact they are killed, by water and mildew starts during dry weather.

Mildew is difficult to treat once the symptoms are visible, try to remove and destroy affected foliage to reduce the number of spores. You might try a horticultural oil which can actually control mildew after you see it. Most other treatments only prevent infections and do not control them once they have started. Try baking soda, potassium bicarbonate, or sulphur. The bicarbonates can be mixed with oil, sulphur should not. Chemical fungicides are not particularly effective.
alison_froglady
Original Author
19 years ago
Thankyou so much. When you say they are specific to that particular plant, does that mean that just my daisies can be affected and all my other planting around them will not become affected with the mildew. That is a relief if it is so.
If the mildew spores are killed by water then they are certainly dead here. The rain hasn't stopped in days.I suppose though that as it dries up, because the air is still humid it will start it all again. I will try the baking soda. Do I put it on the leaves or pour onto the soil?
Alison

Here is a link that might be useful: Alisons pond and garden
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I'm sure someone on this forum once recommended spraying with milk as an anti-mildew measure, the rationale being that mildew likes alkali and the going-off milk is weakly acid. Did I get that right?

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