Downy mildew of Impatiens
Impatiens downy mildew, known as Plasmoparaobducens (Schrtiter) Schroter, is harmful all over the world. It mainly harms the leaves and reduces the ornamental value.
The primary chlorotic plaques on the affected leaves were irregular and became yellowish brown or brown necrotic spots in the later stage; there was a white mildew on the back of the leaves, which was thick and dense, and the whole leaf could be covered when it occurred seriously, resulting in scorched leaves and affected ornamental.
The pathogen is called impatiens axis downy mildew, which belongs to oomycetes. 2Mel 5 branches cyst peduncle, protruding from stomata, upper uniaxial branch 4 Mel 7 times, terminal branch straight, conical, apex obtusely flat; sporangium size 10-27 × 10 Mel 18 (um), nearly round.
The disease has an annual cycle and there is no obvious overwintering period. In the north, the pathogen overwinters in the soil with oospores. In the following year, the oospores were transmitted by current or Rain Water sputtering in a suitable environment. In the south, the pathogen carried out primary infection and re-infection with sporangia. After sporangium germinated, the sporangia produced by the disease were transmitted by airflow and re-infected, so that the disease spread. Temperature 15 ℃, high humidity or large temperature difference between day and night, heavy fog, heavy soil viscosity, low-lying terrain are easy to occur; summer and autumn continuous rain, rainy days, heavy rainfall serious disease or pandemic.
Prevention and cure method
The main results are as follows: (1) strengthen cultivation management, fertilize and irrigate reasonably, adjust ventilation and light transmission, and improve plant resistance. Select high-lying land for planting, timely drainage after rain, maintain appropriate temperature and humidity, clean up the disease residue, and reduce the source of disease.
(2) select disease-resistant varieties.
(3) at the initial stage of chemical prevention and treatment, 70% ethylphosphine manganese zinc wettable powder 500 times solution or 64% germicidal alum wettable powder 400% 500 times solution, 72% Kelu wettable powder 600 times solution, once every 10 days, prevention and treatment 2 Mel 3 times.
Commonly used agents ethyl phosphine manganese zinc wettable powder, disinfectant alum wettable powder, Kelu wettable powder.
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Impatiens cultivation
Impatiens, also known as henna, is an annual flower native to southern China and tropical plains of Asia. There are many varieties and rich colors, including red, pink, purple, yellow and white, as well as complex colors, which are very gorgeous. Generally divided into single and double two categories, single-petal plants conical, tall and robust, up to 80 cm. The flowering sequence is higher and higher from the bottom up, and the flowering period can be up to 1 month. Double-petal varieties have shorter plants, generally less than 40 cm, flat-topped, flowering with flower buds all around the terminal bud, and blooming neatly from top to bottom at one time.
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Growing environment of primrose
Sex likes cool summer, warm winter climate and humid, ventilated environment. It is required that there should be plenty of sunshine, and it is appropriate for China and Japan to shine. Not cold-resistant, not resistant to high temperature, avoid strong direct sunlight, not resistant to shade, slightly resistant to drought, resistant to moisture and fertilizer. It grows best in sandy loam which is loose, fertile, well drained and rich in humus. Light and temperature like cool, avoid high temperature is the basic temperature requirements of primroses. The suitable growth temperature is 20 ℃ in daytime and 5-10 ℃ at night. It can grow well at 12-22 ℃. The temperature over-quotient plants grow slowly and grow at lower temperatures.
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