Anonymous added on May 29, 2017 | Answered

Can you re-apply a pre-emergent, once shrub roses are blooming? Have black/brown spots on leaves and leaves look like something is eating on them.

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Certified GKH Gardening Expert
Answered on May 30, 2017

I would give the rosebushes a treatment of Bayer Tree and Shrub Granules per the label instructions for Ornamentals/Roses. It is a systemic disease control product and has some food in it too so that it helps strengthen the bush to help fight the disease attack. A pre-emergent usually refers to an herbicide which is not what is wanted here, so I am assuming that you mean a systemic. Yes you can reapply systemics once blooming has started. If the rosebushes turn out to have black spot fungus attacking them, you may need to spray them with a product called Mancozeb, it is available on and will stop most black spot attacks in their tracks.

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