knockout rose problem
My Knockout Roses: have flourished for several years. But not this year.
I prune the bushes back substantially each year during the winter, usually in February. This year I pruned them back further. It took longer for them to grow out and make flowers but they seemed normal at first.
Then they lost blooms and leaves and plants looked like they were dying.
In the past few weeks they have gradually gotten some new leaf growth but minimal. They do not fully leaf out and have odd leaves. Very few blooms. There may be half a dozen blooms now on 58 bushes. There seems to be no growth of canes.
They were sprayed once with liquid Sevin brand XLR Plus. Active ingredient: carbaryl insecticide (1-naphthyl N-methylcarbamate). That was maybe 2 months ago and I thought it must have caused the damage but on the internet I see references of folks using Sevin on Knockouts.
They have been fertilized with Ozmocote and about Ã¯Â¿Â½ the plants have had Miracle Grow gardensoil placed around them, maybe 3 weeks ago. I see no apparent difference between plants with the soil vs those without.
My questions are:
What caused this ?
What can I do for them?
thank you very much