Question
We live in Gastonia, NC near Charlotte, NC and are having a problem with a group of our knock out roses.  Last summer we noticed the canes were turning black and losing their leaves.  It started on one bush and has affected 3 of 5 of our bushes.  We have trimmed all of the dead, black stems and sprayed Daconil once. We cut more canes today and sprayed them again.  We don't know what could be wrong.  Thanks for your help.

Answer
Knock Out is usually a very healthy rose and will take a lot of abuse. However it is still just a rose and if conditions are right, can get disease problems. What you are describing is called canker and is caused by a fungus. This particular fungus is very contagious. What happens is that if a cane is accidently damaged, too much fertilizer which burns a cane, bad drainage, there is die back on a cane during the winter or it was damaged when purchased, then this fungus sets in. It can easily be spread by pruning one rose and then using the pruners on another as the pruners should be cleaned with rubbing alcohol. This fungus spreads too rapidly for organic solutions. I would prune the infected plants right down to 6 inches or until the middle of the canes are a pale green with no brown showing. Then wipe the pruners off with the alcohol and cut down another one on the same bush. Just keep doing this until you are satisfied that all the canes on the rose bushes are free of the fungus. Spray the plants again plus all around the base in case there could be fungal spores there too. During the spring or until it gets warm, make sure you water gently around the bottom of the rose bushes as water on the canes will encourage it to come back. Then when the weather warms up, you should have no more problems as these spores like cool weather. Hope this helps.