Hi,
I have some white powdery mildew on one of my rose bushes. I sprayed it with chemical, now do I prune off the affected areas? What causes this too much water or too little? I live in southern California and these are mature roses. Please help.........
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Lyonsden77
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The Helpful Gardener
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Powdery mildew is usually caused by late day watering. Try to water in the early AM to give the leaves time to dry off; staying wet through the evening allows the spores to adhere and gives them cultural conditions to get started. Don't water foliage if it's not going to be able to dry off quickly. A good organic solution is a cup of milk in a gallon of water; spray it on the leaves and it will not only kill mildew, but will prevent reoccurence.
As for removing the leaves, if the spray was effective, it shouldn't be necessary. If you're going to remove leaves you may as well not spray and now you are eliminating the mildew the old fashioned, organic way. Fungicides, like insecticides, can eliminate some good guys (mycorrhizhal fungii), so I only use them when absolutely necessary...
Scott
As for removing the leaves, if the spray was effective, it shouldn't be necessary. If you're going to remove leaves you may as well not spray and now you are eliminating the mildew the old fashioned, organic way. Fungicides, like insecticides, can eliminate some good guys (mycorrhizhal fungii), so I only use them when absolutely necessary...
Scott