Occurrence Patterns and Control Methods of Garlic Blight

I. Symptoms Garlic blight mainly damages the leaves. In the early stage of infection, pale white to light yellow water-soaked spots appear in the middle of the leaf or at the leaf tip, with light green edges. The lesions expand quickly, and within 3 to 5 days half of the leaf or the entire leaf wilts and droops. When humidity is high, the lesions rot, causing the whole plant to die.

II. Pathogen and Transmission Routes The pathogen overwinters as mycelium and chlamydospores in the underground parts of diseased plants or in the soil. When conditions are suitable the following spring, the diseased parts produce sporangia and zoospores. The zoospores spread through wind, rain and irrigation water, causing primary infection and secondary infection.

III. Influencing Factors

1. Climate Heavy precipitation, frequent foggy days and high temperatures make the disease more likely to occur. Generally, the disease is more severe when the temperature is 25°C to 32°C, the relative humidity is above 95%, and water droplets are present.

2. Variety and Sowing Date There are certain differences in susceptibility among varieties. Sowing too late leads to severe damage. Sowing at the right time according to local conditions is a key step.

3. Fertilizer and Water Management Applying more organic fertilizer, phosphate fertilizer and potassium fertilizer results in milder disease, while plots with early and excessive nitrogen application have more severe disease. Under different conditions, poor soil fertility leads to more severe disease. Frequent watering and high field humidity make the disease more likely to occur. Therefore, when watering, observe the soil moisture and weather changes.

4. Reasonable Close Planting The suitable planting density for garlic is 35,000 plants per mu. The greater the density, the more severe the disease, mainly because excessive density leads to a large leaf area index in the field, poor ventilation and light penetration for the lower leaves, and high field humidity, which favors the rapid reproduction of the pathogen.

IV. Integrated Control Measures

1. Select disease-resistant varieties According to local conditions, choose better local or non-local varieties such as "Gaojiao" and "Puke".

2. Pay attention to drainage to prevent excessive humidity, and water reasonably.

3. After harvest, promptly remove diseased residues and bury or burn them in a centralized manner.

4. Advocate applying more organic fertilizer and biological bacterial fertilizer and potassium fertilizer, and less nitrogen fertilizer, to enhance disease resistance.

5. In the early stage of the disease, spray 72% Kelu wettable powder at 800 to 1000 times dilution, 72.2% Pulike aqueous solution at 800 times dilution, or Dacheng M-45 wettable powder at 600 to 800 times dilution. Spray once every 7 to 10 days, for 2 treatments.