Key Points of Green Prevention and Control Technology for Leek Major Pests and Diseases

I. Prevention and Control Goals

The goal is to achieve a pest and disease management rate of over 90% in leek cultivation areas, with an overall control effect of over 85%. This ensures that the damage rate is kept below 10%, guaranteeing the green and safe production of leeks.

II. Prevention and Control Strategies

In accordance with the plant protection principle of “prevention first, integrated pest management,” the strategy coordinates the use of health cultivation techniques, biological control methods, and scientific pesticide application strategies to ensure effective suppression and control of major leek pests and diseases. Specific measures include early pest and disease monitoring, health cultivation management, physical control methods, as well as biological control and precise pesticide application.

III. Control Targets

1.	Main Diseases: Gray mold, downy mildew, etc.
2.	Main Pests: Leek maggot (including leek late-eye fungus gnat, and other late-eye fungus gnats), thrips, leek borer, aphids, etc.

IV. Prevention and Control Measures

(A) Enhanced Monitoring 1. Pest Monitoring: • Use blue boards or blue boards with thrips pheromone to monitor leek thrips; • Use black boards to monitor leek maggot adults; • Install sex pheromone traps to monitor leek borer; • Conduct regular manual surveys to monitor disease occurrences.

(B) Health Cultivation 1. Selecting Resistant Varieties: Choose leek varieties with good marketability and local adaptability, which are resistant or tolerant to pests and diseases. 2. Crop Rotation: Rotate with non-lily plants every 3–5 years to break the pest and disease transmission chain and reduce occurrence rates. 3. Proper Fertilization: Combine deep plowing with sufficient basal fertilization, and apply topdressing appropriately. It is recommended to use cake fertilizer or well-fermented organic manure, avoiding excessive use of chemical fertilizers. 4. Drainage and Ventilation: Ensure timely drainage in open field cultivation areas during rainy days, and regulate ventilation in greenhouses to maintain air circulation, reducing the risk of diseases caused by high humidity. 5. Field Cleanliness: Timely remove plant residues and decayed leaves from the field, bury or compost them to reduce habitats for pests and diseases.

(C) “Sun Exposure and High Temperature Film Covering” Control Method

From late April to mid-September, on days with strong sunlight (light intensity greater than 55,000 lux), cover leek fields with a 0.10–0.12 mm thick light blue drip-free film (cut leeks 1–2 days before covering). The film should be firmly pressed around the edges, extending 50 cm beyond the field. Once the soil temperature reaches 40°C at a 5 cm depth and remains above this for over 3 hours, immediately remove the film to cool the soil and prevent root damage. After removing the film, wait for the soil temperature to recover to an appropriate level, then irrigate promptly to help leek seedlings recover.

(D) Biological Control 1. Microbial Agents Application: • Apply microbial agents like Trichoderma or Bacillus species before covering the greenhouse to control gray mold and downy mildew; • When leeks reach 5 cm in height, spray with Bacillus subtilis or Trichoderma for disease prevention; • During the leek maggot larval stage, apply entomopathogenic fungi such as Metarhizium or Beauveria bassiana in the form of granules (e.g., 200 million spores/gram of Metarhizium CQMa421 granules) during overcast weather or periods of weak sunlight. 2. Nematode Application: Apply entomopathogenic nematodes during spring and autumn, when the local temperature is between 15–25°C. Apply during overcast weather or in the early morning/evening when sunlight is weak. Apply nematode formulations at approximately 100 million nematodes per acre to effectively control leek maggots.

(E) Scientific Pesticide Application 1. Disease Control: • For gray mold, use fungicides like carbendazim, cymoxanil, or fludioxonil; • For downy mildew, recommended fungicides include metalaxyl-M, cyazofamid, or fluazinam. Pesticide selection must comply with the Ministry of Agriculture’s “Pesticide Residue Risk Control Guidelines for Specialty Minor Crops” regarding dosage, frequency of application, and safety intervals. 2. Pest Control: • For leek maggot, use agents like matrine, azadirachtin, methomyl, thiamethoxam, or flufenoxuron, applying either spraying or “double-dose treatment”; • For aphids, select agents such as matrine, high-efficiency cypermethrin, or imidacloprid; • For leek thrips, use thiamethoxam or other recommended agents; • For leek borer, use abamectin, cypermethrin, or other suitable agents.

V. Precautions

1.	Rotate Pesticides: Pesticides should be rotated according to different modes of action to prevent resistance. The frequency of application and safety intervals must strictly adhere to the requirements of the pesticides used.
2.	Safety Interval for Carbendazim: Carbendazim, commonly used for gray mold control, has a long safety interval. If the harvest period is less than 21 days, avoid using it or delay harvest to ensure pesticide residues are within acceptable limits.

By integrating the above green prevention and control technologies, leek production’s green safety can be effectively improved, minimizing the impact of pests and diseases on yield and quality, while also reducing the negative environmental impact and promoting sustainable production of leeks.