Occurrence of blight of impatiens

Balsamine blight is common in China, and it is a common disease in impatiens cultivation. The disease mainly infects the root and stem.

After the symptom rhizome was damaged, there was black constriction, and there was white mildew in the disease part when the environment was humid. The pathogen spread rapidly and occurred seriously, which led to the wilting and drying up of the upper leaves within a few days, and the whole plant died in serious cases.

The pathogen RhizoctoniasolaniKuhn is called Rhizoctonia solanacearum, which belongs to the subphylum of semiknowns. The bacteria did not produce spores, the mycelium grew to a certain time, the sclerotia was interwoven to form a sclerotia, the sclerotia was flat and round at first, and then became irregular, small and light brown, and the mycelium was produced when the sclerotia germinated. Behavior is not common, when the humidity is high, there is a thin grayish-brown bacterial membrane on the surface of the stem and leaf disease near the soil surface, namely basidium and basidiospore. The basidium is colorless, stick-shaped to barrel-shaped, with 4 peduncles at the tip, and one basidiospore on each peduncle. The basidiospore is colorless and Obovate.

The pathogen overwintered mainly by hyphae or sclerotia in the disease residue or soil, and the mycelium camp in the soil was saprophytic and did not dormant. When the organs come into contact with the diseased soil, the bacteria can be transmitted, and under the condition of water film, the healthy leaves in contact with the diseased part will be infected. In addition, seeds, farm tools and bacteria-carrying compost can be transmitted over a long distance. The growth temperature of mycelium was 6-40 ℃, and the optimum temperature for mycelium growth was 20-30 ℃, especially 25-30 ℃. Hyphae like cold, cool and dry soil, in a high humidity environment, 98% of the general relative humidity sclerotia can germinate and invade, plants with weak resistance, soil temperature and humidity is too high or too low, sticky heavy, are conducive to the disease.

Prevention and cure method

The main results are as follows: (1) Agricultural control, strengthen cultivation management, fertilize and irrigate reasonably, regulate ventilation and light transmission, and improve plant resistance. Timely drainage after rain, maintain appropriate temperature and humidity, clean up the disease residue, burn or destroy collectively, and reduce the source of disease.

(2) improve clayey soil and reduce the occurrence of diseases.

(3) more resistant varieties were selected.

(4) Chemical control spraying 75% chlorothalonil wettable powder at the initial stage of the disease, or 60% Dofu wettable powder 500x solution, 20% methyl rifampicin EC 1200 times.

Commonly used agents chlorothalonil wettable powder, Duofu wettable powder, methyl ribavirin EC.