Peony plants are perennials that continue to give you a gorgeous flower garden year after year. They grow best in USDA plant-hardiness zones three through eight and can live for up to 100 years. Although peony plants require little maintenance, you'll want to keep an eye out for a few common pests and diseases that will wreck havoc if not caught early on.  

Japanese Beetles

According to the Old Farmer's Almanac, Japanese beetles are responsible for significant crop damage throughout the Eastern and Midwestern United States. There are very few plants that aren't susceptible to these tiny creatures. When examining your peony plants, look for a group of tiny bugs are are just 1/2 inch in length. They will appear copper in color with a bluish-colored head. They also have tiny white hairs on their stomachs. The best way to combat these critters is to pick them off of your plants and place them in a bucket of soapy water. 

Botrytis Blight

If you live in an area that experiences a lot of rain, then you'll need to watch your peony plants for botrytis blight. The first sign of trouble will be leafy shoots that begin to droop. This will be followed by a host of fungal spores that are either black or brown in color. When the problem isn't addressed, the disease will progress so that the stalks are nothing but gray mold and the flower buds a ball of black. Cornell University suggests removing all parts of the plant that are infected with botrytis blight and throwing them away inside a paper bag. Treat all of the remaining plants with a fungicide that has neem oil listed as an ingredient. 

Foliar Nematodes

Foliar nematodes are minuscule insects that attach peony plants above ground. The first sign of trouble are brown lesions that form between the veins of your plant's leaves. If left untreated, the foliar nematodes may kill your peonies before spreading to other plants in your flower garden. The University of Minnesota recommends removing any infected leaves and then spraying the plants with insecticidal soap. Afterward, keep the plants dry and inspect them on a regular basis. 

Powdery Mildew

Another fungal disease to watch out for is powdery mildew. This problem is easily spotted as leaves, stems, and flowers begin to appear to have a coating that resembles a white powder. Although this disease rarely kills plants, it can deform the flowers. The University of California says that making sure the plants have adequate exposure to the sun is your best form of defense, but once a problem is already present, you'll need a use a horticultural oil spray to get rid of it.