In the process of rape planting, there is often a disease that has a great impact on the yield of rape. It is Downy mildew. Let's learn about the causes and prevention measures of this disease together.
Causes of rape Downy mildew
1. Variety resistance. Generally, Brassica napus is relatively resistant to diseases, followed by Brassica juncea, and Brassica napus is susceptible to diseases.
2. Rapeseed continuous cropping. The occurrence of Downy mildew in continuous cropping fields was significantly higher than that in rotation fields, and the incidence rate was 20% higher than that in rotation fields.
3. Improper field management. Low lying terrain, poor drainage, high planting density, and excessive nitrogen fertilizer application can easily exacerbate the development of diseases.
4. Temperature and humidity. Continuous rainy days, lack of sunlight, and low temperatures (around 16 ℃) can also cause its onset.
Control of rape Downy mildew
Cultivation measures
Timely arrange the sowing time according to the meteorological conditions of that year, reasonably plant densely, and apply fertilizer scientifically. Increase the application amount of organic fertilizer, reasonably mix nitrogen, phosphorus, and potassium fertilizers, and spray trace elements such as boron and manganese. Timely ditch and drain after rain.
chemical control
Seedling stage is the first infection stage of rape Downy mildew. Spray medicine at seedling stage to kill some bacteria before the first infection, reduce some re infection sources, and use metalaxyl or carbendazim and other chemicals to prevent when the vegetables grow out of true leaves. The flowering period is the susceptible period of rape. If Downy mildew occurs, azoxystrobin, mancozeb, dimethomorpholine, downurea, manganese zinc and other chemicals can be used to control it.
