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Killing black spot on roses #867784

Asked May 09, 2024, 4:25 PM EDT

I would like some advice on killing black spot on roses without killing bees. Have too many to prune them individually. Thank you

Jackson County Oregon

Expert Response

The name of the diease in this case is also how to describe the symptoms. Your rose has a fungal disease known as Black Spot. It affects the leaves and can be prevented by spraying a fungicide in the early spring before the rose leafs out. The recent small rains at night that we have had are friendly to fungal disease. So, if you did not spray a fungicide in the early spring before the rose leafed out, you are now paying the penalty. Youj can try a copper or sulphur commercial fungicide, sprayed every two weeks twice during the second week. Also, pick up or cut off infected leaves and destroy them. Do not allow them to fall and remain on the ground beneath the plant. Next winter, give your plant a fungicide spray once or twice during the dormant season (follow the  instructions on the product for frequency of spraying.) .The disease is ugly, but it won't kill the plant unless you let it overwhelm the leaves, so spraying is not an option; it is a necessity.
marjorie n. OSU Ext. Master Gardener Replied May 10, 2024, 10:26 PM EDT

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