What are the main diseases of radishes? Detailed explanation of control methods
Radish is an annual or biennial herbaceous plant of the genus Raphanus in the Brassicaceae family, and is one of the main vegetables in the root vegetable category. Radish has a large uptake of nitrogen, phosphorus and potassium, and is a high-yielding crop with high fertilizer requirements. For every 4000 kg of radishes produced, approximately 8.5 kg of nitrogen, 3.3 kg of phosphorus pentoxide, and 11.3 kg of potassium oxide need to be absorbed from the soil...
I. Radish downy mildewThe disease mainly affects leaves, but stems, flowers and seed pods can also be affected. Diseased leaves initially develop water-soaked chlorotic spots, which later develop into angular or irregular yellowish-brown lesions. When humidity is high, a white mold layer grows on the underside of the leaves. In severe cases, the lesions merge, causing the leaves to turn yellow and dry up. The pathogen prefers warm, high-humidity conditions. Especially in autumn with frequent rain, high humidity, large day-night temperature differences, and heavy fog and dew, the disease is prone to becoming epidemic. During cultivation, continuous cropping, low-lying plots, excessive planting density, and weak growth make the disease more severe.
Control methods: 25% metalaxyl wettable powder at 800 times dilution, or 64% oxadixyl-mancozeb wettable powder at 400 times dilution, or 58% metalaxyl wettable powder at 600 times dilution, once every 7 days, for 2-3 consecutive applications.
II. Radish black rot
The pathogen mainly affects leaves, causing disease at the leaf margins, appearing as a "V" shape. When the root system is affected, part of the outer skin turns black, or does not change color, with internal dry rot, blackened vascular bundles, and a black dry-rotted pith, or even hollowing. Generally, fields with high temperatures, early sowing, extensive management, and delayed pest control have more severe disease.
Control methods:
(1) Seed disinfection: Soak seeds in 50°C warm water for 20 minutes, or soak seeds in 72% agricultural streptomycin sulfate soluble powder at 3000 times dilution for 2 hours.
(2) Chemical control: In the early stage of disease, use 72% agricultural streptomycin sulfate wettable powder at 4000 times dilution, or 77% copper hydroxide wettable powder at 500 times dilution, once every 7 days, for 2-3 consecutive applications.
III. Radish soft rot
It mainly affects the fleshy root and leaf stalks. The disease first develops where the root contacts the ground, with the diseased area showing water-soaked soft rot. With a gentle pull by hand, it breaks off at the diseased spot. The pathogen prefers high temperature and high humidity conditions. Excessive rain and over-irrigation make the disease more likely to occur.
Control methods:
(1) Use water rationally, avoid flood irrigation, and drain promptly after rain.
(2) Remove diseased plants promptly when found, and disinfect the root holes with lime. (3) After harvest, thoroughly remove diseased and residual plants and bury them deep to kill the bacteria.
(3) Apply chemicals promptly in the early stage of disease. 72% agricultural streptomycin soluble powder at 400 times dilution, or 50% ambam aqueous solution at 800 times dilution, or 70% dexon wettable powder at 800 times dilution can be used for control.
IV. Radish black spot
It mainly affects leaves. The lesions are round, nearly round or irregular, light brown to brown, and in severe cases the leaves turn yellow. When temperatures are relatively high and there is frequent rain and high humidity, the disease increases.
Control methods: In the early stage of disease, spray with 75% chlorothalonil wettable powder at 600 times dilution, or 50% iprodione wettable powder at 1000 times dilution. Once every 7 days, for 2-3 consecutive applications.