First, the harm symptoms: Lettuce Sclerotinia soft rot mainly divided into root rot and stem rot two types. After the root rot-type roots were infested by Sclerotinia sclerotiorum, overgrown white mycelium was formed at the base of the stems, gradually forming many small white particles, which overflowed with water droplets, and the later small particles turned into black sclerotia, sometimes many sclerotial nucleus links. In the form of lumps, the roots are rotted; the stem base rot mainly infects the stem base, and the base of the stem develops lesions. The young lettuce is infected, and the mycelium in the lower part of the plant expands upwards. The diseased plants are rapidly soft and rot lodging.
Second, transmission and disease conditions: bacteria to sclerotia attached to the plant strains on the summer or winter, the spring sclerotia germinate to grow mycelium, from the roots of the lettuce or stem base invade, the Ministry of disease spread to the ground to spread. After the lodging of the diseased plants, they were infected by the infected strains. In the process of disease expansion, the vegetative mycelium produced a large number of sclerotia. Since the sclerotia of the ploughed soil fell into the soil, it became the source of infestation at the beginning of the year.
Third, prevention and control methods:
(1) The implementation of rotations or rotations with other vegetables.
(2) Foreign reports of Streptovercasporium can effectively inhibit Sclerotinia, which can be further demonstrated.
(3) Selection of disease-resistant varieties. Such as red lettuce, hanging red silk, red round leaves and other red antibacterial nuclear disease varieties and cabbage lettuce: Wanli heart lettuce, crisp heart lettuce, and Sclerotinia also more resistant to disease.
(4) to cultivate age-appropriate seedlings, seedling age of 6-8 true leaves is appropriate.
(5) Advocate the use of compost made from Japanese enzyme bacteria or 7.5 to 10 kg of phosphate fertilizer per 667 square meters, and 10 to 15 kg of potash fertilizer. After the opening of the plant, the top dressing will be applied. Also, 0.2% to 0.5% of the compound fertilizer may be sprayed or sprayed. Double fluid increases resistance to disease.
(6) Set soil with soil to improve the quality of the cover film so that the film will adhere to the ground and prevent the growth of weeds.
(7) Covering with black mulch film at appropriate time, the uncovered apium discs are blocked under the membrane so that they do not receive sufficient scattered light, most of them cannot complete their development process, and the probability of primary infection is greatly reduced. The timely removal of diseased leaves or the removal of diseased plants is deeply buried and combined with chemical control. However, in the high temperature period, precautions must be taken to prevent the mulching of the mulching film. If necessary, a thin layer of fine soil can be sprinkled on the membrane, or the water can be cooled or delayed. Planting period to avoid high temperature damage.
(8) Begin spraying 50% thiophanate-methyl sulfur suspension agent 700 times or 50% acetaminophen wettable powder 1000 times, 50% fast keratin or Nongliling WP 1500 times, 40 % Sclerotium net wettable powder 500 times, 20% methyltricaltochlor EC 1000 times. Every 7 to 10 days, continuous control of 3 to 4 times.
(9) The smog method or dust method can be adopted in the cultivation of greenhouses, and the medication should be stopped 3 days before harvesting.
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