Massive die off in Martha Gonzales [Knock out rose] that started and keeps going along the row. No insects visible.

Question

These are my sister’s and she showed me the die off. No insects visible, an organic gardener by nature and we could not come up with a reason. Roses are usually carefree plants and I could not offer any reason as to why, unless a disease which is unusual in a rose group. We have had a wet season but these have been here for more than 6-8 years.
Any help would be greatly appreciated.

Answer 1

That kind of die off signals some catastrophic event! This can happen when something gets dumped onto the soils around or near where the rosebushes are growing. Herbicide drift is also a possibility. Big dogs relieving themselves all over the bushes can cause dieback as well. Another possibility is that something is directing intense reflected sunlight onto the bushes in such a way that it is like using a magnifying glass and the sun to burn something. There also can be rodents attacking the root systems from below or even root eating insects below ground that cannot be seen.

I would start by having the soils tested to see what that shows. If it is something poured or sprayed onto the soils area, it will show up. Time to do some in-depth investigating for sure.

You might consider digging a small ditch between the dead bushes and the ones that are still okay. If you see any sort of rodent channels, get some deep reaching metal edging material and place it in the center of the ditch going down as far as possible. This will slow the rodents down while you decide how to get rid of them.

https://www.gardeningknowhow.com/plant-problems/pests/animals/garden-mouse-control.htm