Prevention and control of diseases and insect pests of tree peony

Peony virus disease

Symptoms: peony ringspot virus (PRV) produces the same concentric round spots of dark green and light green on the leaves, at the same time, there are small necrotic spots, plants are not dwarfed, TRV also changes in different sizes of ring spots or wheel spots, sometimes irregular, while PLCV causes obvious dwarfing, weak twisting of the lower branches and yellowing and curling of the leaves.

Pathogen:

(1) Peony ringspot virus (Peonyringspotvirus,PRV) virus spheroid, 27 nm. It is difficult to be inoculated with sap friction and can be transmitted by aphids.

(2) there are two kinds of tobacco fragility virus (TobaccorattlevirusTRV) virus particles, the long one is 190nm and the short one is 45nm. Can be inoculated with sap, it is reported that nematode, dodder and peony seeds can transmit virus.

(3) Peony leaf curl virus (Peonyleafcurlvirus,PLCV) is transmitted by grafting.

Route of infection: propagate separately with diseased plants, or used as grafting material and a large number of aphids occurred in the field.

Host plants: PRV and PLCV are harmful to peony and peony; in addition to peony and peony, TRV is also harmful to hyacinth, daffodils, tulips and other flowers.

Powdery mildew of peony

Symptoms: White powdery mildew spots are produced on the leaves, which are often expanded and connected into pieces, or even cover the whole leaves and stems, causing premature senescence or death of the plant.

Pathogen: ErysipheaquilegiaeDC.etMer., is called powdery mildew.

Route of transmission: the bacteria overwintered on the diseased body with closed cysts (small black spots on the diseased leaves), producing ascospores and causing primary infection. Continue to re-infect with conidia.

Prevention and cure method

1. Strengthen cultivation and management.

The application of nitrogen fertilizer should not be too much, and potassium and calcium fertilizer should be properly increased to enhance plant growth and disease resistance. Timely pruning and plastic surgery, remove diseased shoots and diseased leaves, and improve ventilation and light transmission between plants. When potted indoors, it should be placed in a place with good ventilation and sufficient light. Control indoor temperature and humidity in winter and pay attention to ventilation at night. Before moving into the greenhouse (or cold cellar) in late autumn and early winter, you should check carefully and find that the diseased leaves and tips should be cut off and burned immediately so as not to spread indoors.

2. Chemical control

At the initial stage of the disease, spraying 1000 times solution of 15% verapamil wettable powder or 1000 times solution of 70% methyl topiramate wettable powder had good prevention and control effect. The residual period of trimethoprim can reach 20-25 days. After spraying, the white layer of the diseased part is dark gray, dry and disappear.

Peony brown spot

Peony brown spot occurs in the late growth stage of peony.

Symptoms: pale spots of different sizes appear on the leaf surface, usually round spots with a diameter of 3Mel and 7mm. There are less than 1 or 2 spots in a leaf, and up to 30 spots in a leaf. The middle part of the lesion gradually turns brown, with very small black spots scattered on the front, fluffy under the magnifying glass, with several layers of concentric wheel patterns. Large irregular plaques are formed when adjacent plaques merge. When it is serious, the whole leaf surface turns into a disease spot and dies. The leaf spot on the back of the leaf is dark brown and the wheel pattern is not obvious.

Pathogen: the pathogen is Cercospora discolored (CercosporavariicolorWinter).