Q.burning bushes
I have 3 Burning Bushes left out of 4 and all 3 have yellowish spots on the leaves. What causes this? I live in Frederick, CO. and last winter we had some really warm weather. Then we got hit with a Polar Vortex. I lost 1 of my bushes. I also lost a smoke bush to that. But now the remaining 3 burning bushes have yellowish spots on the leaves. We have had a lot of rain. Is it something I need to add to the soil or something else?
Yellowing leaves can be an indication of watering issues. Either to much or to little.
Once the plant is stressed they can become vulnerable to insects or disease.
I would make adjustment to watering and treat the plants with Neem OIl. It works as both an insecticide and fungicide. I would even treat weekly for the remaining growing season.
https://www.gardeningknowhow.com/plant-problems/pests/pesticides/neem-oil-uses.htm
https://www.gardeningknowhow.com/ornamental/shrubs/burning-bush/burning-bush-care.htm