Have you ever walked out into your yard and saw something a little off with your roses? Maybe a little leaf curl here, a little powdery white substance there? Powdery mildew is a fungal disease that can impact all rose breeds. However, certain environmental factors can lead to powdery mildew being more prevalent in certain areas of the country. Here in the Pacific Northwest (PNW), with its mild temperatures and high humidity environment, powdery mildew is common. Powdery mildew usually becomes very apparent in the spring and fall when warmer days and colder evening temperatures come about. Unlike other fungal diseases, water on the leaf surfaces prevents powdery mildew spores from germinating. However, high humidity environments with mild temperatures are the ideal environment to spread this disease. How do we keep it off of our roses?
First and foremost, is taking preventative measures:
- Remove dead foliage from the surrounding area to prevent overwintering environments;
- Remove any cane or leaves that exhibits signs of powdery mildew;
- Treat the plant with fungicide to help prevent powdery mildew spores from duplicating and spreading.
- Make sure that your rose plants have adequate nutrients and water to allow the plant to maintain its natural immune defenses.
If you already see powdery mildew on foliage or canes, you can take the same steps as above, but know that this is a disease that must be acted upon quickly.
A copper fungicide spray goes a long way to helping a plant eradicate powdery mildew. Our favorite is Bonide as it is quick and effective.
We also like to mix mint and tea tree oil in a mix with water to help keep bugs (especially aphids) away in early spring. If you have special solutions you use, feel free to share in the comments below.