Powdery mildew of Euonymus tomentosa

Symptoms: the disease harms leaves and shoots. Most of the disease spots were distributed on the front of the leaves. At the beginning of the disease, there are many small white round spots scattered on the susceptible leaves, which gradually expand, heal each other and become irregular spots. When the disease is serious, the infection rate of new shoots can reach 10%. White powder appeared on the whole leaf and shoot surface. The diseased leaves gradually fade green, turn yellow, and finally turn brown and black. The diseased part is deformed, the diseased leaf is shrunk, and the diseased tip is twisted and atrophied.

The pathogen is Oidiumeuonymi (Are.) Sacc., which belongs to the subphylum Trichospora, Trichospora, Trichospora and Fungi.

The law of disease: the pathogen overwintered in the diseased plant by mycelium. In the spring of the following year, the pathogen produced a large number of conidia, which were spread by airflow and were harmful to infection. The conidia can be re-infected repeatedly. The pathogen parasites on the surface of the branches and leaves of the host and produces haustorium to penetrate into the epidermal cells to absorb nutrients. High temperature in summer is not conducive to the development of diseases. The disease of the plants planted in the shade was serious, while the disease of the adjacent sunny plants was little or no. The disease of young leaves and new shoots is serious, while that of old leaves is light.

Prevention and treatment: ① reduces the source of infection: remove fallen leaves and diseased shoots in winter and destroy them centrally. ② medicament prevention and cure: at the initial stage of the disease, spray 1500-2000 times solution of 25% chlorpheniramine wettable powder, or 80-1000 times liquid of 70% topazine wettable powder, or Baume 0.3-0.5 degree stone sulfur mixture, or 50% bacilli wettable powder 1500 times, spray 2-3 times every 10-15 days.