Peonies are reasonably disease-resistant, perennial flowering plants popular in both commercial and home growing environments. Peonies prefer full sun for part of the day and a regular watering pattern. Keeping peony plants healthy minimizes the risk of pest infestation and disease.
Flower thrips are tiny insects that feed on the buds of peonies or at the base of the petals. Because the flower thrip is so small, damage is usually observed before the insects. Stippled, discolored leaves and flowers and small, black clumps of feces around the site of the discoloration may indicate the presence of these insects, according to the University of California’s Agriculture and Natural Resources.
Poenies infected with botrytis, or blight, display sudden wilting of young shoots. Black or chocolate rot is usually visible on stems below ground level; just above ground level, the fungus is visible. Flowers die or become brown, and irregular brown lesions form on the leaves. Botrytis can be controlled by applying copper spray.
Peony ringspot is a rogue viral disease infecting random peony plants. Ringspot is not considered a serious infection as the only real problem it causes is discolored concentric bands on leaves and less frequently small spots of tissue death. No chemical control is available as of 2010 and infected plants should be destroyed, reports Kansas State University.