Control methods of Brown spot of Peony

Peony brown spot is a common disease in the later growth stage of peony. Symptoms: pale spots of different sizes appear on the surface of the leaves, usually round spots with a diameter of 3mm and 7mm. There are 1-2 spots in a leaf, and up to 30 spots in a leaf. The central part of the lesion gradually turns brown, with very small black spots scattered on the front, fluffy under a 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 disease spot on the back of the leaf is dark brown and the wheel pattern is not obvious. Pathogen: the pathogen of brown spot is CercosporavariicolorWinter, which belongs to Trichospora and Trichospora. Conidiophores pale, occasionally septum or flexion, unbranched, size 10 ~ 35 × 2 ~ 4 microns. The conidia are colorless to light brown, with a size of 40 ~ 120 × 2.0 ~ 3.5 microns. Route of transmission: the pathogen overwintered with mycelium and conidia in diseased tissue and fallen leaves and became the source of infection in the second year. Spread by wind and rain, invade directly from the wound. The disease usually occurs from July to September, and is seriously ill when it rains a lot in the typhoon season. The lower leaves became ill first, and the management was relaxed in the later stage. When the basin soil was too dry and too wet, the disease was serious. Prevention and control methods: after harvest, thoroughly remove the diseased and residual plants and fallen leaves, and concentrate on burning.