Is Your Peony Looking Spotty? Here’s What Bacterial Blight Looks Like and What to Do About It

If your peonies have looked a little rough this season, you’re not imagining it. This spring’s heavy rainfall created ideal conditions for a plant disease called bacterial blight, and we’ve been seeing it show up more than usual in landscapes across the area.

Why This Year Has Been Worse Than Usual

Bacteria like this one need moisture to survive, spread, and infect new tissue. A typical Indiana summer dries out enough by mid-season to slow this disease down on its own. But with the extended wet stretch we’ve had this spring, conditions have stayed favorable for the bacteria longer than normal, meaning the blight has had more opportunity to spread through affected plantings.
What You Can Do About It

The good news is that a few adjustments to how you care for your peonies can make a real difference:

• Water at the base, not overhead. Sprinklers and overhead watering keep leaves wet longer, which is exactly what this bacteria needs to spread. Switching to soaker hoses or hand watering at the soil line helps keep foliage dry.
• Give your plants some breathing room. Peonies planted too close together stay damp longer after rain or dew, since airflow gets blocked. Thinning out crowded plantings helps leaves dry faster.
• Avoid working with wet plants. Bacteria can enter through small wounds, so pruning, deadheading, or even walking through plants while they’re still wet from rain or dew gives the disease an easy way in. Wait until foliage has dried before handling your peonies.
• Copper-based treatments can help protect healthy growth. These products work best as a preventive measure on unaffected tissue. They won’t reverse damage that’s already there, but they can help stop the disease from spreading further.