What is wrong with my roses?

Asked June 27, 2017, 3:02 PM EDT

The last 2 years when my roses open up, they look like this. What is causing this? I have sprayed a fungicide but they still look like this. The rest of the rose bush looks good and is healthy.

Isabella County Michigan roses

1 Response

There are three possibilities:

  1. Frost damage: In April and May (both years) there were several days that were quite warm and the evening temperatures dipped into frost temperatures that could have caused damage to the bud and the developing petals. In this case, the damage is already done and there is no treatment.
  2. Thrips: these are very minute insects that can cause discoloring and deformation of the flowers. These insects are hard to control. Remove the spent flowers. Insecticidal soaps may be of some help, but thrips are often in the buds and deep in the flowers, so contact may be difficult. If you use a pesticide for thrip control, the trick is not using it when the plants are flowering, as a pesticide may also kill pollinators. Before using anything, you can try to spot any insects in or on the flowers using a good magnifying lens, or you may wish to send a sample for accurate diagnostics to MSU diagnostic services. For information and details go to :https://pestid.msu.edu/
  3. Botrytis blight: this is fungal and since you have treated with a fungicide would seem least likely.