Peonies and myrtle dead

Asked July 16, 2017, 1:29 PM EDT

My peonies have a gray cast to the leaves that is spreading throughout all the peonies in my garden. The myrtle which was mounding , green and lush is dying out. Can you tell me what to do?

Wayne County Michigan flowers: annuals and herbaceous perennials

1 Response

Good Afternoon.

Looking at your peonies it seems like they have powdery mildew. I am attaching some helpful information regarding this type of mildew.

Powdery mildew, a fungal disease, appears as a white, powdery fungal growth of mycelium and spores on the upper leaf surface. Leaves and flowers may become infected, wither and die.

Conditions including high humidity, warm days, and cool nights favor powdery mildew development. The disease is common in crowded plantings and in areas with restricted air movement.

There is no cure for infected plants however powdery mildew can usually be managed with timely use of preventative fungicides coupled with the use of disease resistant varieties. Preventative fungicide sprays help protect healthy plant tissue from infection. Products containing active ingredients such as triforine, chlorothalonil and sulfur are labeled for control of powdery mildew. Be sure to follow label directions. Spraying won’t cure already-infected leaves, but it will prevent the disease from spreading to the rest of the plant.

For more information on resistant varieties and fungicides for management of powdery mildews, see BP-5-W: Powdery Mildew of Plants (pdf file) .

Common Problems of Myrtle

Leafhoppers, scale insects, aphids, etc. may attack the plants. Stem blight is considered as a serious disease of V. Minor. A fungus called Phoma exigua var. exigua grows in moist soil and plant debris. The fungal infection results in dark brown to black lesions on the stems. The affected stems and their foliage turn black or brown. The fungus girdles a stem at its base and eventually the stem dies. The newly growing stems may also die. The disease can be difficult to control. It is necessary to apply fungicides at the very onset of the symptoms. You may use Thiophanate-methyl (Bonide Bonomyl, Dragon 3336, or Ferti-lome Halt), Copper sulfate pentahydrate (Phyton 27), or Mancozeb (Bonide Mancozeb or Dragon Mancozeb). You should strictly follow the instructions on the labels.
Read more at Buzzle:

I couldn't tell from the picture if there were any lesions on the stems, but have you stayed with a regular water schedule in this hot weather lately?

I hope this information has been helpful to you. Good Luck!