Symptoms

This disease occurs more seriously in the seedling stage. Initially in the leaf blade produced nearly round small green spots, later the entire leaf color becomes light or appear green mottled between light and dark, with the development of the disease leaf crumpling, twisted deformed, and finally the whole plant necrosis. In addition to the young leaves appear uneven mottling, the back of the old leaves sometimes produce black-brown necrotic spots, or accompanied by leaf vein necrosis, and finally dwarfed and deformed, twisted petiole, inside and outside the proportion of the leaf is seriously out of proportion, or the flower bulb becomes smaller, or not at all (color version of the twenty-sixth, 149).

Pathogen

This disease is mainly caused by turnip mosaic virus (TuMV), but in some areas it is also caused by cucumber mosaic virus (CMV), tobacco mosaic virus (TMV) or radish mosaic virus (RMV) and other viruses alone or mixed with TuMV. Turnip mosaic virus granules are linear, size 700-800 nm × 12-18 nm, loss temperature 55-60 ℃, 10 minutes, dilution limit point 1000 times, in vitro retention time 48-72 hours, through aphids or sap friction contact transmission. Under the natural conditions in the field, it mainly relies on aphids to transmit the virus.TuMV also infests a variety of vegetables such as spinach, corns, capers, mustard and so on.

Characteristics of the disease

This disease is found in warm areas, where cruciferous vegetables are grown year-round without significant overwintering, and other vegetables in the cruciferous family, wild rape and cruciferous weeds are the source of the initial infestation. In areas where cruciferous vegetables are not grown in winter, the virus overwinters on stored cabbage, kale, turnips, or overwintered spinach; in areas where cruciferous vegetables are grown in winter, the virus overwinters in the host. By the peach aphid, vegetable constrictor aphid, kale aphid, etc. will be the source of the virus to a variety of cruciferous vegetables, spring, summer, fall and winter mutual infection, resulting in a variety of vegetable disease. High temperature and drought, high ground temperature, the host root growth and development is affected, resistance to disease significantly reduced, and aphids reproduce fast, frequent activities, resulting in widespread disease. If the management of sloppy, dry soil, lack of water and fertilizer, the disease is serious. There are differences in disease resistance between different varieties.

Methods of prevention and control

(1) Select more resistant varieties according to local conditions. Such as Ri Green, Green Ridge, Gastar or other more heat-resistant varieties that are more resistant to the disease.

(2) Cultivation measures. Reasonable inter-, set, crop rotation; summer and fall planting, away from other cruciferous vegetables; found heavy disease plants pulled out in time.

(3) Strengthen management. The use of shade net or non-woven fabric cover cultivation technology; increase the application of organic fertilizer; high temperature and dry season pay attention to watering and aphid control very well, to control the occurrence and spread of disease.

(4) early onset of pharmaceutical control. Optional spraying 20% virus A wettable powder 500 times, or 1.5% phytophthora emulsion 1000 times, or spraying compound foliar fertilizer to inhibit the onset of disease and enhance the host resistance.