Whether in the garden or asCut flower in the vase– Peonies become an eye-catching eye-catcher everywhere. In the garden they enchant us from April to June with their magnificent flowers and their delicate scent. But problems such as brown leaves or a missing flower can quickly spoil our enjoyment of these attractive plants. Read on to learn how to identify and treat peonies diseases and pests.
The peony has spotty leaves? This is a viral disease
Garden plants can occasionally be attacked by viruses. In about 90 percent of cases, the reason for peony diseases is the purchase of poor-quality planting material. But even if you purchased a healthy peony root from a nursery, aphids and other sucking insects can spread the virus from neighboring diseased plants. Viruses are often found on weeds, cucumbers, potatoes, peppers, strawberries and raspberries.
You will see the discoloration on the leaves of your newcomers after 3 to 5 years, and in a few more years the weakened plants will already be suffering from a variety of fungal diseases.
Which viruses occur in peonies?
In contrast to tulips or gladioli, fortunately not all peony varieties react to the virus with serious illness. Most of the old varieties show no external signs of the disease, but the modern American hybrids become seriously ill and die quickly from the pathogenic fungi that quickly develop thereafter. However, with good cultivation techniques and protection against fungal diseases, every peony can develop beautiful flowers without any problems.
As a rule, viral diseases in peonies are rarely caused by a single pathogen; there is usually a mixed infection. In botanical gardens they are now easily detected using laboratory methods. Hobby gardeners don't necessarily need to know these, but we will still list the most important viruses:
- Spotty leaves, for example, are a symptom of yellowBean mosaic virus (BYMV).
- Cucumber mosaic virus (CMV), rhesus mosaic virus (ArMV), and yellow dwarf virus (BYDV) are usually detected on specimens with leaf growth problems.
- Narcissus mosaic virus and Tomato aspermy virus are detected on individual plants with signs of fine leaf spots merging.
- In most cases, a complex infection includes TAV, CMV, ArMV, CarMV (Carnation Mottle Virus), TMV (Tobacco Mosaic Virus) in various combinations.
Tobacco rattle virus is very common in peonies
If you notice a problem with your peonies, it is almost always related to Tobacco rattle virus (TRV), also known as Tobacco rattle virus. It was also previously known as peony ring spot virus.
Any gardener can recognize the symptoms of this disease by taking a close look at his peonies in May-June. Rings and half rings, as well as stripes of various shapes and colors - from light green, greenish-yellow to bright yellow - appear on the leaves between the veins. They merge into one another and form the characteristic marbled pattern.
The severity of the viral infection depends on the variety
Gardeners report on peony varieties that delight them with their wonderful flowers for 40 years despite a viral disease and leaf discoloration. The early blooming peony 'Red Charme'(Paeonia x hybrida ‘Red Charme’)for example is one of these special varieties.
What fungal diseases occur in peonies?
Unfortunately, peonies are very susceptible to fungal diseases. The most well-known pathogen is Botrytis paeoniae, also known as gray mold, which causes dry rot.
Grauschimmel (Botrytis)
The pathogen is the mold Botrytis cinerea, B. paeoniae. Usually in the spring, immediately after the regrowth of young shoots, brown spots appear at their base, then the stems rot in this place. The gray mold coating and the small black fungal spots are easy to see. The stems wilt and then fall off. Sometimes rot appears already 10-12 cm above the base.
Large brown spots appear on the leaves, which gradually dry out in dry weather, and in high humidity become covered with a gray mold and rot. During the flowering period the same can be observed on the buds. Smaller buds turn black, wither or rot, while larger buds turn brown and bloom poorly.
The disease develops very quickly, with severe damage: the bushes fall apart, the stems fall and dry out. The fungus lives on plant residues and in the rhizomes of peonies, causing them to rot. It spreads when it rains and is spread by ants.
Cold rainy weather in spring and summer as well as sudden temperature changes contribute to the active development of mushrooms. The fungal disease can develop faster in moist, clayey soils, in excessively watered and thickened, poorly ventilated bushes.
In general, high humidity, excessive nitrogen content in the soil and shading of plants contribute to the development of the disease. Early varieties and especially hybrids are most affected.
The rust fungus Cronartium flaccidum
The first signs of the disease are observed in mid-summer, shortly after flowering. Brown, yellowish-brown or brown spots with a purple border appear on the upper side of the leaves. Small yellowish-brown or orange pads form on the underside containing fungal spores that are easily spread by the wind and infect new plants. In late summer, yellowish-brown, horn-like curved columns appear between the pads and completely cover the underside of the leaves, causing them to curl and dry out. Under favorable conditions, the disease can spread within 2-3 days and affect large areas of peonies.
In the fall, the spores infect pine trees, the fungus's intermediate host. These trees can become a perennial source of infection.
Damp, warm weather promotes the development of the disease. Under such conditions, the pathogen spreads intensively, causing the leaves to dry out as early as July and shortening the growing season, which weakens the plants and negatively affects their winter hardiness and flowering the next year.
Cladosporiosis – brown spot disease caused by Cladosporium paeoniae
The disease usually occurs in the first half of summer and is more common in southern Germany. Large brown or dark purple spots form on the leaves, which gradually grow, merge into each other and can cover their entire surface. Over time, the spots become darker and the leaves appear burnt. In wet weather, a dark gray coating appears on their underside. Stems, buds and flowers are sometimes affected.
Elongated reddish-brown spots usually form on young shoots, then the stem becomes dark and covered with gray fungal coating. The buds turn brown and the petals fall off. The spores of the fungus overwinter on fallen leaves.
Septoria disease caused by Septoria macrospora
The leaves and stems of peonies are particularly affected. The first symptoms of the disease appear on the leaves in June or July: brown or yellowish-brown, round or elongated spots with a light center and a dark purple edge form on both sides of the leaves. Gradually, the spots merge and acquire a light brown color with an ashy tint.
The disease first manifests itself on the lower leaves and then spreads along the stem.
If the disease is severe, the leaves will shrivel completely, but may not fall off for a long time. The disease weakens plants and affects winter hardiness and flowering the next year.
Root rot
The pathogens can be fungi of the genera Fusarium, Botrytis, Rhizoctonia or Sclerotinia. They cause rotting of roots, stems, cuttings and plant death. The disease is widespread in all zones and is detected during transplantation or propagation by division of the rootstock. The affected areas of roots and rhizomes turn brown, soften, rot and die. When the humidity is increased, a whitish, grayish or pinkish coating forms. The soil and infected rhizomes are the source of infection. As a rule, weakened plants, cuttings and bushes divided during transplanting become sick. Increased moisture and high acidity of the soil contribute to the development of the disease.
Peony pests
Here's the good news: Pests on peonies are much less common than fungal diseases, and don't cause much damage in a well-maintained garden. The caterpillars of the owl butterfly gnaw the buds of peonies planted in the shade or partial shade. The bronze beetle, root-knot nematodes and ants can also annoy the flower grower.
Shiny gold rose beetle (Cetonia aurata)
Everyone has seen these beautiful shiny beetles before. They feed on the petals and stamens of flowers. The beetles like flowers that are bright in color and have a strong scent. They can be seen every spring, first on lilacs, then on irises and early peonies.
Root-knot nematodes
Nematodes, also called roundworms, settle in the roots of peonies and cause knotty swellings. After the roots rot, they migrate to new peonies growing nearby.
Common lawn ant
The ant's body is reddish-yellow, 4-7 mm long. It feeds on sweet bud secretions and eats flower petals.
Pest control
You can simply collect the beetles early in the morning. Ants can be easily controlled by spraying their nests with modern anticides.
Ants carry aphids, and aphids transmit viruses to plants. Spraying the plants with any preparations from the groups of nicotine and pyrethroids helpsexcellent against aphidsand caterpillars. For example with a solution from “Actara” or similar.
Nematodes are rare, but it's still worth keeping an eye out for. It is necessary to combat them with a strict examination of the roots during transplantation and burning of all divisions with gnarled swellings of the roots and severe rot lesions.
More on the topicfind out here.
Fighting viral diseases in peonies
There is no cure for viruses in peonies. Every spring, check your peony seedlings and mark infected bushes. It's better to burn these.
If a variety is very valuable to you, plant it in the fall away from the main plants. Divide them into small branches with 1-2 buds. Choose the strongest shoots and leave a small but healthy part of the roots.
When a diseased peony is transplanted in this way every two years, through clonal selection of the healthiest root sections, the peony is free from rot and sometimes viruses.
It is very important to plant peonies further away from strawberries, raspberries, potatoes, cucumbers and tomatoes to prevent the spread of sucking pests.
Preventive measures against fungal diseases
Although it is difficult to control the gray mold Botrytis, it is possible. In early spring, carefully remove soil around plantings of capricious American hybrids and treat with a fungicide such as “Score” or “Chorus”. Then mulch the peony bush with a layer of fresh sand, without any organic material. Do three treatments: in April, beginning and end of May.
If the variety is susceptible to damage from fungal diseases, spray preventatively in May with Score or Chorus, and in late summer with “Ridomil Gold”.
Organic farming methods help prevent disease. Never use fresh manure and fresh grass for planting peonies. Mulch only with old compost every fall. Fertilizewith low-nitrogen, mineral-organic fertilizers. Peonies also react very well to compost tea. The microorganisms it contains ideally suppress putrefactive bacteria.
In autumn, cut back all shoots of the perennial to 5 cm above the ground and place the slightly poisonous clippings in a compost heap. The result of all these measures are healthy plants and magnificent flowers.
