Joe Pye Weed is an easy-to-grow perennial that is native to North America. A big part of what makes this wildflower so low maintenance is that not many issues or diseases impact growth. Joe Pye Weed is not disease resistant, but is rarely damaged severely. If you know what common diseases to look out for, you can often prevent problems with your plant. Learning treatments for common diseases ensures you can keep your Joe Pye Weed happily growing all season long.
Joe Pye Weed Powdery Mildew
Powdery mildew is the most common issue to face Joe Pye Weed. Many different species of fungi can cause this fungal disease. A powdery mildew outbreak will likely happen when the days are cool and the nights are humid. Humid, crowded growing conditions are conducive to powdery mildew. Powdery mildew can stunt growth and kill the plant.
Identifying Powdery Mildew
White, powdery splotches that cover the foliage are a clear sign of powdery mildew. Infected leaves will eventually turn yellow and die, and the mildew will spread to other leaves on the plant.
Photo by Joey Williamson, Clemson Extension
Treating Powdery Mildew
Treat powdery mildew on Joe Pye Weed by applying a fungicide. Catching the infection early will pose the best chance of recovery. Remove severely infected parts of the plant, and destroy the removed vegetation to prevent the fungus from spreading. Reduce the odds of a future powdery mildew outbreak by pruning overgrown plants, relocating crowded plants, and watering plants when thirsty.
Joe Pye Weed Rust
Another fungal disease, rust, is caused by Pucciniales fungi. This disease is unsightly and slowly kills leaves. Infected Joe Pye Weed will experience leaf drop, resulting in stunted growth. Extreme cases of rust can be fatal if the plant loses enough foliage.
Identifying Rust
Rust appears as small brown or orange dots on the foliage of Joe Pye Weed. The spots will grow larger, connecting with nearby spots and engulfing the entire leaf.
Treating Rust
Treat rust on Joe Pye Weed by spraying the plant with a fungicide. Repeat the spray as necessary to ensure there are no remaining spores. Remove foliage with significant damage, and destroy the leaves to ensure the fungus does not infect other plants. Rust is more likely to occur in damp environments, so leave plenty of space around Joe Pye Weed when planting to allow adequate airflow. Select cultivars that have been bred to resist disease.
Joe Pye Weed Disease Chart
| Disease | Identifying | Treating |
|---|---|---|
| Powdery Mildew | White mold on leaves | Fungicide & air circulation |
| Rust | Brown or orange spots on leaves | Fungicide & air circulation |
 |
Author Alison Cotsonas - Published 07-06-2023 |