Control of spot blight of Magnolia paniculata

Spot blight of Cymbidium grandiflora is a common disease of Cymbidium.

Symptom

Leaves infected with primary purplish red raised spots, gradually expanded into withered yellow. With the expansion of the disease, the spot becomes oval to nearly square or irregular, the size of 0.8~3cm, with the leaf surface flat or slightly raised, the edge reddish brown, the center gray to grayish brown, wrinkled. In the later stage, there are irregular black spots in the upper arrangement of disease spots, that is, the conidia of pathogens. In severe cases, there are many large spots on the leaves, resulting in the death of the whole leaf.

Pathogen

Pleurocytosporasp. It is called a kind of coccidiospora, which belongs to semi-known fungi. Conidia dark brown, oblate to flask-shaped, initially buried, orifice exposed after maturity, size 190 ~ 339.6 × 150 ~ 165 (μ m), solitary or multiple aggregates, some multi-chambers, multiple single chambers when mature. Conidiophores are colorless and branched at the base or upper part, with a size of 12 ~ 24 × 1 ~ 15 (μ m). The single cell of conidia is colorless, straight or slightly curved, blunt round at both ends, sausage-shaped, size 3.8 ~ 6.3 × 1 ~ 1.3 (μ m).

Route of transmission and conditions of onset

The pathogen overwintered in the diseased tissue with mycelium or conidia, and the conidia were released in the next spring to spread through wind, rain and watering, invading from the micro-wound and carrying out primary infection and re-infection. Wet and rainy weather is easy to occur and expand, which occurs from January to November every year. It can occur all year round under the condition of shed.

Prevention and cure method

The main results are as follows: (1) when changing the basin in spring, we should apply sufficient base fertilizer and put it under the shade shed, apply fertilizer in time during the growing period, strengthen indoor ventilation, avoid direct sunlight and maintain a certain humidity. It is found that the disease spot should be cut off in time, watering from the edge of the basin, do not drop water into the leaves, often wash the dust on the leaves, keep the leaves bright and reduce the infection of bacteria. When the orchid enters the dormant period, watering should be controlled.

(2) if necessary, spray 1000 times of 50% water soluble powder or 40% chlorothalonil suspension, 30% copper chloride suspension, 40% bromofol wettable powder and more than 80%? Fu? Zinc (Luheng No. 2) wettable powder 800 times solution, once every 7 to 15 days, prevention and treatment for 3 times.