Main diseases of garlic bolts and garlic during storage

In recent years, garlic planting area in Jinxiang County of Shandong Province is about 500,000 mu, accounting for 40% of the cultivated area of the whole county. There are 700 constant temperature warehouses in the county, with a storage capacity of 450,000 tons. Garlic sprouts and garlic heads are collected intensively from late April to early and middle May every year. Most garlic sprouts and garlic heads are stored except for a small amount of local consumption and transportation. There will be loss during storage, and the decay caused by various diseases is the main reason for the loss during storage.

1. Garlic stem diseases during storage

1.1 gray mold

1.1.1 Symptom sprouts are most susceptible to disease, withered tissue produces white thin mold layer, and then develops to bracts, the diseased part is pale yellow water-stained, densely white to gray mold layer. The base of stem and other injured or diseased parts are also vulnerable. In the early stage, the disease spots are long, pale brown and depressed along the stem, and in the later stage, the disease spots expand, rot upward from the base, or rot in other parts to form broken strips, and produce white to gray mold layers. It has a strong musty smell.

1.1.2 It is a fungus that causes the disease. The suitable temperature for its growth is 15~21℃. The germination rate of spores is high under the condition of relative humidity above 95%, especially in the presence of water drops. The pathogen was mainly brought in from the field by garlic sprouts, and the residual pathogen in the warehouse was also related to the disease. Pathogens mostly infected from both ends of garlic stem and injured or other pathological parts.

The suitable storage temperature for garlic sprouts was 0℃. However, at low temperature of about 0℃, the pathogen still has certain activity ability. If the temperature is too high, it is not only beneficial to infection and reproduction of the pathogen, but also accelerates the atrophy and aging of the bud and stalk base, reduces the disease resistance and accelerates the development of the disease.

In CA storage with relative humidity of 90%~100%, the withered sprouts were wet, especially when soaked by dew.

The disease was serious under high oxygen condition, and 3%~5% oxygen concentration could inhibit mildew better than 6.5%.

1.2 virus disease

1.2.1 Symptoms of yellow spots formed on garlic sprouts or longitudinal yellow stripes along the stem, also known as flower face, yellow spots and so on. There are more in the middle and lower parts of garlic sprouts and less near the bracts. With the prolongation of storage period, macula tissue depression, necrosis, infection mold and decay.

1.2.2 Garlic bolt virus was mainly infected by garlic mosaic virus and garlic latent virus. Garlic mosaic virus infection alone can cause obvious stripe mosaic symptoms in garlic. Garlic mosaic virus is transmitted by seed garlic subculture and non-persistent transmission mainly by aphids in the field. Virus propagation in plants was not only limited to leaves, pseudostems and garlic sprouts above ground, but also transferred to bulbs below ground. High temperature and drought in garlic growing season, poor management conditions, large occurrence of aphids and continuous cropping or adjacent cropping of Allium host plants are serious.

All garlic sprouts were infected by disease in the field, and the yellow spots were sunken, necrotic and rotten in the middle and late storage period. The disease developed rapidly under the condition of not timely precooling and high storage temperature.

1.3 Carbon dioxide injury and hypoxia injury

1.3.1 Symptoms Carbon dioxide injury makes garlic stalks appear yellow spots, then expand into round or irregular spots, depression, followed by garlic stalks into water-soaked soft strips, commonly known as boiled garlic sprouts, sprouts necrosis. The concave spots are often connected into pieces, and when infected with germs, they rot to form broken strips. The packaging bag has a strong alcohol smell. Hypoxia injury was mainly manifested as white or yellow flower buds, dark green stems, soft shoots, and slight water loss.

1.3.2 The pathogen is caused by inappropriate high carbon dioxide or low oxygen conditions. Damage occurs when the carbon dioxide concentration in the general storage environment exceeds 10%~15%. The permeability of the injured garlic sprouts increased greatly before the disease appeared, which caused physiological disorders. With the extension of storage period, garlic sprouts 'tolerance to carbon dioxide weakened, and they were vulnerable in the middle and late storage period. Hypoxic injury occurs when oxygen levels are below 1% for a prolonged period of time.

1.4 garlic dry rot

1.4.1 Symptoms Garlic petal base was yellow brown, gradually dry, the disease can produce orange-red mold layer.

1.4.2 Garlic dry rot is a fungal disease. The optimum temperature for growth of the pathogen was 25~28℃, and the optimum temperature for disease onset was 28~32℃.

The bacteria are stored with garlic, which rots during storage. Wounds at the base of stems and roots are conducive to the invasion of germs. Garlic disease was most serious when it was near harvest. Garlic is most perishable when the storage temperature is about 28℃, but it is very light at 8℃.

2 Methods of Prevention

2.1 Strict quality requirements before storage to select products from disease-free or disease-free areas are effective measures to avoid virus diseases at present, and are also effective in preventing other infectious diseases. During the growth period, attention should be paid to the prevention and control of gray mold, dry rot, etc. 1~5 days before harvest, spray 50% Pythium WP 1500 times solution, or 40% Compound Carbendazim 800 times solution, or 50% Prohydantoin WP 1000 times solution, or 70% Thiophanate-methyl WP 600 times solution, etc. Harvest in sunny days at the right time to avoid rain, sun exposure and damage. Quickly precool to 0℃.

2.2 Before use, use 8~ 10g sulfur and 2 times sawdust per cubic meter to ignite and fumigate for 24 hours, or spray with 1%~2% formalin. All shelves and packaging bags used should be washed with 0.5% bleaching powder solution and dried before use. Absorbent paper or cotton balls soaked with 50% sec-butylamine solution can be placed in the packaging bag, and the dosage is calculated according to 0.1m1 per kilogram of garlic sprouts.

2.3 The storage conditions were controlled as follows: ambient temperature of-0.5℃~0.5℃, oxygen 3%~5%, carbon dioxide 5%~8%.