What are the methods for controlling pests and diseases in peony cultivation

Peony virus disease

Symptoms: Peony ringspot virus (PRV) produces concentric ring-like round spots of dark green and light green on the leaves, along with small necrotic spots; the plant does not become dwarfed. TRV also causes ringspots or ring spots of varying sizes, sometimes irregular in shape, while PLCV causes obvious dwarfing of the plant, with the lower branches thin and twisted, and the leaves yellowing and curling.

Pathogen:

(1) Peony ringspot virus (Peonyringspotvirus, PRV) virus particles are spherical, 27 nanometers. Difficult to inoculate by sap rubbing; can be transmitted by aphids.

(2) Tobacco rattle virus (Tobaccorattlevirus TRV) has two types of virus particles, the long one being 190 nanometers and the short one 45~115 nanometers. It can be inoculated by sap; it is reported that nematodes, dodder and peony seeds can all transmit the virus.

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

Transmission routes: Propagation by dividing diseased plants, or use as grafting material, as well as massive occurrence of aphids in the field.

Host plants: PRV and PLCV harm Chinese peony and tree peony; TRV, in addition to Chinese peony and tree peony, also harms flowers such as hyacinth, narcissus and tulip.

Peony powdery mildew

Symptoms: White powdery mildew spots appear on the leaves, often expanding and connecting into patches, even covering the entire leaves and stems of the plant, causing premature aging or death of the plant.

Pathogen: Erysipheaquilegiae DC.et Mer., called columbine powdery mildew fungus.

Transmission routes: The pathogen overwinters on diseased residues as cleistothecia (small black dots on diseased leaves), producing ascospores that cause primary infection. Conidia continuously cause secondary infection.

Control methods

1. Strengthen cultivation management

Nitrogen fertilizer should not be applied excessively; potassium and calcium fertilizers should be appropriately increased to enhance plant vigor and improve disease resistance. Prune and shape in a timely manner, remove diseased shoots and diseased leaves, and improve ventilation and light penetration conditions between plants. When potted indoors, place in a well-ventilated area with ample light. In winter, control indoor temperature and humidity, and pay attention to ventilation at night. Before moving into the greenhouse (or cold cellar) in late autumn and early winter, inspect carefully, and immediately prune and burn any diseased leaves and shoots found, so as to avoid bringing them indoors and spreading the disease.

2. Chemical control

In the early stage of the disease, spray 15% triadimefon wettable powder at 1000 times dilution, or 70% thiophanate-methyl wettable powder at 1000 times dilution, both of which have good control effects. The residual effect period of triadimefon can reach 20~25 days; after spraying, the white layer on the diseased parts turns dark gray, shrinks and disappears.

Peony brown spot disease

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

Symptoms: Pale white spots of varying sizes appear on the leaf surface, generally round spots with a diameter of 3-7 millimeters. In a single leaf there may be as few as 1~2 lesions, or as many as 30 lesions. The center of the lesion gradually turns brown, with very fine small black dots scattered on the upper surface, downy under a magnifying glass, with several layers of concentric rings. When adjacent lesions merge, they form irregular large lesions. In severe cases, the entire leaf surface becomes lesions and dies. On the back of the leaf, the spots are dark brown, with indistinct rings.

Pathogen: The pathogen is Cercosporavariicolor Winter.