Peonies are appreciated for their large and showy flowers, which come in a variety of colors and forms. Generally, peonies have problems with only a few type of insect pests. Most of these insects are simply nuisances and can be easily managed. Severe infestations occasionally occur and can result in stunted growth of the plant, bud failure and root damage.
Scale insects can adversely effect peony plants. They have small gray-brown shells and are little under 1/8 of an inch in length. These insects can be seen on the leaves and stalks of plants in late summer. They suck plant fluids to feed. Small infestations are usually not a problem, though heavy infestations can challenge the plant's health.
Peony thrips are little insects, about 1/16 of an inch long, that resemble flies. The have feathery wings and long tube-like bodies. Peony thrips damage peony leaves, buds and flowers by sucking plant fluids from them. These insects are tiny enough to enter buds and feed. This can cause the buds to fail to open.
Peonies are also attacked by bulb mites. These pearly white arachnids are around 1/32 of an inch long. They feed on peony roots, particularly damaged ones, and often turn the flesh reddish brown. The roots can become soft and may rot from the resulting injury.
Ants are often seen on peonies and, while their presence may be alarming, they actually do no harm to the plant. They are simply interested in the sweet liquid that is secreted by peony flower buds. The only risk from ants is that they might spread diseases, such as the botrytis fungus, by contact.