Yellowing and spots on roses

Asked June 18, 2019, 1:31 PM EDT

My name is Cary and I work at Sponsors. We have 4 rose bushes and all of the leaves are turning yellow with spots, but the flowers are fine. Do you know what this is? Can I treat it? Will this hurt the plants? They get watered twice a day and are connected to an underground sprinkler system so the leaves do not get wet.

Lane County Oregon roses

1 Response

Watering 2 x a day is excessive for an in ground plant as it can prevent adequate oxygen from infiltrating to the roots. Watering only very shallowly and often can damage the deeper roots. That said, the disease is rose leaf spot. Some varieties are resistant but many are very susceptible and badly damaged. Go to the following link for a full write up on this. In the future chose very disease resistant varieties.
https://pnwhandbooks.org/plantdisease/host-disease/rose-rosa-spp-hybrids-black-spot