Answer: There are two cases of dark stems. One is that there are many round and oval spots on the base of the stem. There are black spots on the base of the stem. Severe ones will surround the base of the stem. This is black shank disease. The other is the black base of the stem, white mold above the wet, is a black root disease.
Control technology: 1. Seed disinfection. It can be soaked in warm water at 50°C for 20 minutes, or with 0.4% of seed weight in 50% formamide. 2. Improve seedling technology. It is best to use plug seedlings. The nursery soils should be selected from the soil of the wheat or corn in the substrate or the field, and can not be used to plant vegetables, especially the greenhouse Honda soil. 3. Seedbed and soil treatment. 40% pentachloronitrobenzene powder and 50% thiram can be mixed in equal amounts, 9-10 grams per square meter, mixed with 3-4 kilograms of fine dry soil and mix well, and one third is spread on the seedbed. Two-thirds cover the seeds. 4. Strengthen seedbed management. Can not be watered during the nursery period, and can only be sprayed with a watering can on a sunny day. After the seedlings are unearthed, they must be planted in time and be ventilated and ventilated. 5. Early onset of drug control. Can use 75% chlorothalonil (Dakkonin) WP 600 times, 40% polysulfide suspension 500 to 600 times, 60% Duofu WP 600 times spray, spray once every 9 days, even spray 2 ~ 3 times. The leaves of cabbage and cauliflower are waxy. Generally, the spray is not easy to adhere. Before spraying, it is best to add a small amount of spreading agent in the pharmaceutical, such as Roushuitong, etc., and a small amount of washing powder may also be added.
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