Prevention and Control of Downy mildew of Zinseng

Hundred-day grass, also known as hundred-day chrysanthemum, step by step, etc., is an annual herbaceous flower of Compositae. Originally from Mexico. The flower is bigger, the color is rich, the flower shape is special, the florescence is longer, has been cultivated all over the country. One of the most important diseases newly found in the breeding research and cultivation practice of zinnia is downy mildew, which is reported as follows:

First, symptoms

The pathogen of downy mildew of zinnia belongs to flagellate subphylum fungi, which can occur at seedling stage, adult stage and flowering stage. The disease at the seedling stage caused the seedlings to yellowing and then withered. The disease of true leaf mostly begins at the back of the lower leaf, and the primary watery spot is light yellowish brown with inconspicuous periphery. After the watery spot lasts for a long time, the disease part grows white mold or polygonal spot when the humidity is high or there is dew. Generally, light green spots appear on the leaf surface, gradually expand to water-stained yellowish brown, become brown after death, and the disease spot is irregular or polygonal due to the limitation of leaf veins. The downy mildew of Zinzu grass spreads rapidly by sporangia (or zoospores) through wind and rain, air flow or irrigation water, serious or after the disease can not be effectively controlled in time, the whole seedling will be infected, and there will be no harvest.

II. Prevention and control methods

First of all, disease-resistant varieties are selected.

2) select seeds and disinfect them. The disease-free plants were treated with 25% metalaxyl wettable powder with 0.3% seed weight before leaving or sowing.

3) the rotation cultivation of plots should be carried out for more than 2 years.

IV) remove diseased leaves and clean the countryside after the previous harvest.

5) the application of fertilizer and water should not be overflowed and flowed everywhere.

VI) 58% metalaxyl can be used for re-used nutrition bowls? The manganese-zinc wettable powder was soaked in 200 times solution.

7) after the central diseased plant was found in the field, the preferred solution was 25% Ruidui wettable powder 800 times, 40% ethyl phosphine aluminum wettable powder 200 times 250 times, 75% Shuangba wettable powder 700 times, 72% Shuangyuqing or 56% frost mildew 500 times 600 times, 58% metalaxyl? Manganese zinc wettable powder 500 times liquid or 70% mancozeb wettable powder 500 times liquid spray control, once every 7 to 10 days, continuous prevention and control for 2 times.