The cause and prevention of celery dead seedlings

This year, the celery growing over the summer and the overwintering cultivation of celery are more serious. The dead seedlings were caused by the fact that there was more rain in the summer and autumn of this year, and that the continuous cropping phenomenon in various places caused serious problems such as soft rot, sclerotinia, black rot, damping-off, and blight.

Celery soft rot: bacterial diseases. Starting from the soft and juicy petioles, water immersion appears at the beginning, and light brown spindles or irregular depressions form. After it was wet and rot, it turned black and smelly, leaving only the epidermis.

Celery Sclerotinia: Damaged celery stems and leaves. The victim was brownish in water, and it was soft and rotted when the humidity was high, and white hyphae grew on the surface. At the end, the stalk tissue rotted fibroid and hollowed in the stem, forming black rat sclerotia.

Celery black rot: Occurs near the base of the root and the base of the petiole, sometimes damaging the root. The disease department became black and rot, and many black spots were born on it. The plant growth was stagnant, and the outer 1-2 layers of leaves fell off due to rot in the base.

Physiosis: After the seeds germinate, the cotyledons and embryos rot and cause rotten species. A water-stained lesion develops on the stem base of the diseased seedling, which then turns yellow-brown and curls up into a line. The seedlings tripped before the cotyledons had wilted. When the seedlings are pulled out, the epidermis that comes into contact with the diseased part can easily fall off. In the cotyledon, it becomes a stuck neck. When the onset is severe and rapid, the fallen seedlings cannot stand upright. The appearance of the seedlings is the same as that of the healthy seedlings, but the base of the stems has already collapsed into a linear shape. White cotton-like mycelium is produced on the surface of the diseased seedlings and nearby ground.

Blight: occurs in the middle and late stages of nursery. Oviform dark brown lesions were produced at the base of the seedlings of the affected seedlings. The early diseased seedlings wilted during the day and recovered at night. After the lesions gradually sag, when the humidity is high, light brown spider silk molds can be seen. After the development of lesions around the stem one week later, the contraction occurs, the roots are dry and wilting, the night can not be restored, and continue to lose water until it dies.

The control method is as follows.

First, the rotation. More than 2 years of rotation.

Second, bed soil disinfection. With old nursery beds, soil disinfection must be performed. Commonly used methods are: formalin disinfection: 2-3 weeks before sowing, the bed soil is loosened, 500 ml of formalin per square meter of nursery bed, add 18-36 kg of water (add water to dryness Decision), evenly poured on the seedbed, and then covered with plastic film on the bed soil. After 3-5 days, remove the cover and loosen the soil. After 2 weeks, the liquid to be fully evaporated and then sown. Carbendazim or thiophanate disinfectant: Use 50% carbendazim or 50% thiophanate, use 8-10 grams per square meter, add 20-30 kg dry fine soil and mix well, use 1/3 of the drug soil before sowing In order to make up soil, 2/3 of the medicine soil is used as cover soil to cover the seeds after sowing. It can also disinfect the soil.

Third, seed processing. Leave seed in disease-free or disease-free plants. Strained seeds were sown with 10% saline before sowing, and the sclerotia were rinsed out, rinsed again with clean water, dried and sown to prevent S. sclerotiorum. Or soak in seeds with warm water at 48°C for 10-15 minutes. Or use 50% of Fairchild WP, ​​or 65% zein zinc WP, and the dosage is 0.3% of seed weight. After rinsing with water, germination can be sown to prevent blight and damping-off.

Fourth, seedbed management. Seed not too dense, after emergence and time seedlings. When the humidity of the seedbed is too large after rain, it should be drained in time, and several times of dry ash in the seedbed. The diseased seedlings were found to be removed in a timely manner and carried deep outside the field or burned.

Fifth, field management. Avoid soil damage and reduce mechanical damage when weeding. The soil should not be too high and avoid burying the petioles in the soil. Drain the water immediately after the rain and reduce the number of watering when the disease occurs. Timely removal of diseased plants, diseased lime sprinkled with lime disinfection. Immediately after harvest, deep soaking or soaking in water can kill the sclerotia in the soil and reduce the source of disease. In summer, it can be closed for 7-10 days, and high temperature can kill surface sclerotia. The use of mulching can stop germs from germination and reduce transmission.

Six, chemical control. In the case of soft rot, 72% of agricultural streptomycin or neomycin can be used for 3000-4000 times; 14% of ammonia hydrothermal agent 350 times; 40% of bacterial spirit 8000 times, using one of the aforementioned agents, or Apply alternately, once every 7-10 days, spray 2-3 times. In the occurrence of black rot, sclerotinia, blight, damping-off disease can be used when 50% fast-king 600 times; 50% acetaminophen 600 times; 50% carbendazim 500 times; 50% ningli Ling 1000 times liquid; 65% Tamyroxin 1000-1500 times liquid, with one of the above-mentioned agents, once every 7-10 days, even spray 2 times.

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