“how to get rid of the white podwer on the leaves of my peonies? ~Paula”
Thank you for the email via Facebook regarding the fungus on your peonies (Paeonia suffruticosa). Sounds like you have a case of Powdery Mildew. Powdery mildew is a white, fluffy buildup on both the top and underside of leaves, eventually resulting in leaf death and loss. Powdery mildew infests numerous types of plants, including peonies. It is not considered as serious a threat on peonies as other plants; however, powdery mildew seems to be increasing as an issue with peonies with the weather conditions we have had this year.
Adequate spacing and thinning discourages powdery mildew development and
spread among plants. Place peonies at least 4 feet apart. Water the roots, avoiding extended periods of moisture presence on flowers and leaves. Prune heavily infected areas, and avoid using high nitrogen fertilizers that promote new growth, which is especially susceptible to powdery mildew development.
For chemical treatment, use fungicides as soon as powdery mildew appears on
peonies to limit damage and protect nearby peonies. Chemical sprays such as
Benomyl (systemic fungicide) or sulfur/fungicidal soap early in the growing
season as a preventative or as soon as symptoms appear. A synthetic
fungicide Baylaton sold as Strike also works well on mildew. Powdery mildew
can develop resistance to every fungicide except sulfur. Apply sulfur to
peonies only on days when the temperature remains below 85 degrees
Fahrenheit, because sulfur damages plants in high temperatures. No matter
which fungicide you choose, always follow label directions to make sure the
product is approved for peonies.
For organic treatment, depending on the severity, spraying it with a baking
soda formula is effective as a preventative when applied regularly. For
active infections spray daily for a week.
1. Mix 1 Tbsp each of baking soda and horticultural oil (dormant
oil/vegetable oil) or a few drops of liquid soap to 1 gallon of water.
Spray weekly making a new mix each time. It will not eliminate the disease
but help control it.
2. Mix 1 tsp baking soda with a few drops of vegetable oil in 1 quart of
water. Spray or paint on the leaves. Works on houseplants, cucurbits &
roses (black spot).
Another suggestion is a solution of 1/3 milk and 2/3 water and spray on
plants. Use every other day.
Neem Oil is also effective in controlling infections. Use 1 oz.(2 Tbsp) of
Neem oil and 1/ 1/2 tsp of dishwashing detergent to one gallon of water.
Spray once a week for two weeks. The combination of Neem and baking soda
treatments is the safest control method. Once the disease takes hold, it is
difficult to control.
© Mertie Mae Botanics LLC and Horticulture Talk!, 2011. Unauthorized use and/or duplication of this material without express and written permission from this blog’s author and/or owner is strictly prohibited. Excerpts and links may be used, provided that full and clear credit is given to Mertie Mae Botanics LLC and Horticulture Talk! with appropriate and specific direction to the original content.