Comprehensive Control Methods for White Spot Disease in Mustard

Mustard is an annual or biennial herbaceous plant of the genus Brassica in the family Brassicaceae. It is a famous specialty vegetable of China, originating in China, and is a commonly cultivated vegetable throughout the country, mostly distributed in the provinces south of the Yangtze River. Mustard prefers cool and moist conditions, dislikes heat and drought, and is slightly tolerant of frost. The average temperature suitable for seed germination is 25°C. The average temperature most suitable for leaf growth of mustard is 15°C, and the temperature most suitable for the growth of edible organs is 8-15°C, but the formation of edible organs in stem mustard and headed mustard requires lower temperatures; generally, leaf mustard has less strict temperature requirements.

Species distribution of mustard

Except for alpine and arid regions, mustard has no distribution boundary in China. It extends east to the coastal provinces, west to the Xinjiang Uygur Autonomous Region, south to Sanya City in Hainan Province, and north to Mohe City in Heilongjiang Province. Mustard is cultivated from the middle and lower reaches of the Yangtze River Plain to the Qinghai-Tibet Plateau.

Growth habits of mustard

Budding, bolting, flowering, and seed setting require vernalization under low temperatures and long-day conditions. In both northern and southern China, autumn sowing is the main practice. In the Yangtze River basin and in the southwest and south China, harvesting takes place in winter or the following spring, while in the north it takes place before frost. Leaf mustard, which is consumed as young plants, can be sown in spring or summer in the south. During the growing period, long-day conditions make bolting more likely, affecting the growth of edible organs.

Comprehensive control of white spot disease in mustard

This disease mainly affects cruciferous vegetables such as mustard, Chinese cabbage, bok choy, cabbage, and radish. It occurs commonly in China and is severe in North China and Northeast China.

Symptoms of white spot disease in mustard:

It mainly affects leaves. At the early stage of the disease, tiny grayish-brown round spots are scattered on the leaf surface, then gradually expand into round, irregularly round, or circular lesions. The center turns grayish-white, with 1-2 inconspicuous concentric rings, and the periphery has a pale white or light yellow-green halo, about 6-18 mm in diameter. In the later stage, the lesions merge with each other to form irregular large lesions. When humid, a light gray moldy substance appears on the underside of the lesions. In the later stage, the lesions turn white and semi-transparent, and then rupture and perforate. Generally, the outer leaves are affected first, and the disease spreads upward.

Conditions for the occurrence of white spot disease in mustard:

This disease is a fungal disease. The pathogen overwinters with diseased plant residues on the soil surface, and can also overwinter on seeds or seed plants. The following spring, it spreads with wind and rain. The temperature range for the occurrence of white spot disease is 5-28°C, with an optimum temperature of 11-23°C. The relative air humidity suitable for disease occurrence is above 60%. It is prone to occur in weather with relatively low temperatures, large temperature differences between day and night, heavy dew in the field, frequent fog, and frequent rain. In addition, factors such as continuous cropping, low-lying terrain, excessive watering, and too early sowing can also cause disease epidemics. Different varieties also differ to some extent in disease resistance.

Comprehensive control methods for mustard:

(1) Variety selection: choose disease-resistant varieties.

(2) Crop rotation: carry out a 2-3 year rotation with non-cruciferous crops.

(3) Seed treatment: select disease-free seed plants to prevent seed contamination. Contaminated seeds can be soaked in warm water at 50°C; or the seeds can be treated at 70°C for 2-3 days to eliminate the pathogen on the seeds.

(4) Field management: sow late at the appropriate time to avoid environmental conditions favorable to disease occurrence; increase the application of organic fertilizer, combine with phosphorus and potassium fertilizers, and supplement trace element fertilizers; promptly remove diseased plants in the field to reduce sources of infection.

(5) Chemical control: at the early stage of disease occurrence, use 15% triamiphos 300-fold solution, 50% meibenxiujing 500-fold solution, 40% duosulfur 600-fold solution, 40% hūnshāliú 600-fold solution, 50% carbendazim 800-fold solution, or Dacotech M-45 400-600-fold solution. Use one of the above chemicals, or apply them alternately, once every 15 days, spraying 2-3 times in succession.