I had a very disappointing year with my roses
. The current problem is with the tip of the plants. While the rest of my plants look healthy, the tip tends become retarded and whither away, thus no flower
buds are forming. The leaves at the top curls up and looks half necrotic. The plants have been watered and fertilized regularly and treated for disease but I haven't used insecticides. I don't see aphids or other insects, except the Japanese beetle invasion earlier. Also, I found granular deposits and matting when I cut down an affected plant to about 4" from the ground. I am in Central Ohio. Any suggestions will be very much appreciated.