A Comprehensive Guide to Viral Disease Prevention and Control in Zhacai Mustard
Zhacai is a variety of mustard. Mustard is commonly used to pickle salty and sour vegetables; its fleshy stem pith is the raw material for Chongqing zhacai, and it belongs to the Brassicaceae family and the Brassica genus. Zhacai is a category within mustard, generally referring to the leafy mustard type, such as jiutou mustard, snow mustard, pig blood mustard, and tofu-skin mustard. Zhacai is a semi-dry, non-fermented pickled vegetable made by pickling stem-type mustard as the raw material. It is one of China's famous specialty products and, together with French pickled cucumbers and German sweet-and-sour cabbage, is known as one of the world's three great pickled vegetables. It first appeared in Fuling, Sichuan, China, in 1898, when it was called “Fuling zhacai”. Because the processing requires pressing out the water from the vegetable, it is called “zhacai” (pressed vegetable).
The mustard used to pickle zhacai is an excellent stem-type mustard, also called fresh vegetable head. Fresh vegetable heads can also be used as a side dish, stir-fried with meat or made into soup, but they are more often used for pickling. They are crisp and tender in texture, delicious in flavor, and rich in nutrients, with a special flavor, a distinctive sour taste and a savory-umami taste, crisp and refreshing. They contain abundant protein, carotene, dietary fiber, minerals and other nutrients essential to the human body, as well as 17 free amino acids including glutamic acid, aspartic acid and alanine. Zhacai can be used as a table condiment, in stir-fries and in soups.
Comprehensive prevention and control of viral disease in zhacai
When sowing zhacai, because autumn temperatures are relatively high, the soil is dry, and aphid damage is severe, it is very unfavorable for sowing and raising zhacai seedlings, and viral disease is easily triggered, greatly affecting yield and quality. Based on many years of practice, the following measures can be taken in production to reduce the harm of viral disease.
1 Practice crop rotation and stay away from sources of the virus
Zhacai seedbeds and field cultivation require rotation of more than 1 year. It is not advisable to choose cruciferous vegetables such as Chinese cabbage and radish as the previous crop or adjacent crop, and keep away from virus-source crops. The seedbed should be fertile and close to a water source.
2 Sow at the appropriate time
According to the climate characteristics of autumn, sowing around October 5 is appropriate. At present, many vegetable growers in northern Zhejiang often sow early, and some even sow before September 20. Because temperatures are still high at this time, there is little rain, the climate is dry, and it is exactly the period when autumn aphids break out heavily, especially winged aphids, which have high density and frequent activity, so the virus spreads quickly and viral disease is prone to occur. Moreover, when sowing early, the amount of aphids in the field after the seedlings are transplanted is also greater, making aphid control difficult. In addition, when sowing too early, the plants are too large before overwintering, and the tumorous stems expand before the new year; after the new year, new tumorous stems form on top of the tumorous stems formed before the new year, creating the phenomenon of large and small tumorous stems on the upper and lower parts. This kind of tumorous stem not only causes a decline in appearance quality, but also increases cellulose and lowers product quality. If sowing is too late, because the plants are too small before the new year and have poor resistance, they are prone to freezing damage, causing slow regrowth after the new year and making it difficult to obtain high yield.
3 Use insect-proof netting for seedling raising and appropriately increase sowing density
Appropriately increasing sowing density helps improve and maintain surface moisture. Generally, sow about 750 g per 667 sq m of seedbed, and the seedlings raised can be transplanted to 4667-5333 sq m of field. If drought occurs during the seedling stage, take drought-resistant and moisture-preserving measures.
Where conditions permit, small arched frames with insect-proof netting can be used for seedling raising, which can completely exclude aphids, reduce opportunities for virus transmission, and help cultivate healthy and strong seedlings. However, when using insect-proof netting for seedling raising, sowing density should be appropriately reduced. At the same time, remove the insect-proof netting about 7 days before transplanting to harden the seedlings so that they can adapt to the field environment as quickly as possible.
4 Strengthen fertilizer and water management
The seedbed should be applied with decomposed human excrement and urine as base fertilizer, 1000 kg per 667 sq m. After emergence, apply a small amount of urea; at the middle stage, apply 5 kg of compound fertilizer once as a drench to increase resistance. At a seedling age of 30-35 days and the 5-6 leaf stage, transplant with soil. During transplanting, cut off excessively long roots with scissors. After planting, if drought occurs, irrigate (or flood-irrigate) to resist drought and ensure seedling survival and recovery.
5 Control aphids promptly and thoroughly
Before sowing, spread 2-3 kg per 667 sq m of seedbed of 5% diazinon granules or 3% Hudijing granules to control underground pests. After emergence, use pesticides such as 10% Yibianjing to control aphids 3 times, respectively in early to mid-October, late October, and before transplanting. After field transplanting, control aphids 2 times. The focus of spraying should be the growing points of the seedlings (plants) and the undersides of leaves, and attention should also be paid to spraying surrounding vegetable plots and weeds.