Symptoms:
Mainly harms the fleshy stems or rhizomes of lettuce balls. The fleshy stems are infected with water-soaked spots, dark green and irregular, and then turn brown and quickly soften and rot. The rhizome part of the disease, the base of the rhizome becomes light brown, gradually soften and rot, when the disease is serious, it can penetrate into the root pith or the knot ball.
Occurrence:
The pathogen stays in the soil with the disease residue and overwinters, spreads by rain splash, water flow and insects, and invades from the wound. Temperature 27 ~ 30 ℃, rainy conditions are prone to disease, continuous field, low-lying waterlogged, hot, humidity heavy disease.
Prevention methods:
1, heavy disease field and grass crops should be implemented 2~3 years crop rotation. Early plowing, sowing at the right time, so that the susceptible period to avoid the high temperature and rainy season. It is strictly prohibited to flood, and watering should be controlled during the epidemic period. Avoid applying unrotted organic fertilizer. Found diseased plants pulled out and buried or burned, after harvesting thoroughly remove the field residues, and then deep soil turning.
2, the onset of the early stage of the disease can choose the following agents for prevention and control:
10% mesocarpine aminoligosaccharides wettable powder 500~1000 times;
20% thiazolium zinc wettable powder 300~500 times + 12% copper turpentine emulsifiable concentrate 600~800 times; evenly sprayed, depending on the condition of the disease once in 7 days.
When the disease is widespread, the following agents can be used for prevention and control:
33.5% copper quinoline suspension 1000~1500 times liquid or 30% copper amphoteric acid wettable powder 200~234 grams/mu or 88% hydromycin soluble powder 2000~3000 times liquid; water spray, depending on the condition of the once every 7 days.