I have a bush that looks like a rosa xanthina (peachy/yellow single five petal roses). This summer has been very hot in Colorado, 27 days over 90 degrees and 7 of those days being over 100 degrees. So I've been trying to not over water my rose bushes but let the hose run under them for at least 15 to 20 minutes long. I have been having whole branches starting to dry up and die. I cut them back at the dead part and it just keeps happening. The rest of the bush is green and blooming. I saw something online last night about die back. But in my case it seems the leaves start to dry up at the top first before anything happens in the stem. With Die back they suggest cutting the plant back to the green happy area and putting some kind of anti-fungal paste at that point to kill what ever may be the problem. Are there anti-fungal pastes sold at nurseries or can I make something at home?