Treating Black Spot Fungus on Mature Peace Lily Plants

Diagnosis

Large black spots, leaf collapse on 8-year-old peace lilies in 18-inch pots. Fertilized with Miracle-Gro. Likely fungal leaf spot exacerbated by water sitting on leaves during cool nights.

Treatment

• Spray with copper fungicide (follow label).
• Water at soil level only; keep foliage dry.
• Improve air circulation.
• Remove severely damaged leaves.

Long-Term

Repot if root-bound (though pots are large). Switch to organic fertilizer (worm castings, compost tea) to build disease resistance. Peace lilies can live decades with good care.