Identification points: mainly garlic bulbs with wounds, especially on garlic bulbs during storage. Peel the garlic cloves, and the small recessed spots with purple-red edges on the scalp, the posterior lesions enlarge, the sag is more obvious, and the black plexus molds, ie the conidiophores and conidia of the pathogens, grow on the lesions.
Occurrence law: Garlic blackhead pathogen is a weak parasitic bacteria, the pathogen is called Alternaria alternata, A. genus, belonging to the semi-bacterial subphylum. When the temperature reaches 20 °C in the middle and late May, the mycelium can produce thick scorpion spores. The conidiophores are born from hyphae or chlamydospores. Conidia are produced on the conidiophores. The conidia spread by airflow. Infected with garlic bulbs with wounds, after harvesting, the garlic will be re-infested during storage under suitable environmental conditions, becoming the source of infection in the second year.
Preventive measures: 1. Strengthen post management. For plots with heavy onset, you can spray 70% chlorothalonil WP 500 times solution or 80% Mancozeb WP 600 times before harvest. During the harvest of garlic, try to avoid stab wounds and severe bruises. It should not be harvested after rain, heavy fog or dew. Before the bag is packed, the mud around the bulb should be removed, and the injured bulbs should be bagged separately and placed separately to avoid cross infection.
2. Strengthen the management of storage and transportation period. The temperature during storage is controlled at 5 to 9 ° C, and the relative humidity is controlled at about 90%. Handle gently during transportation to avoid damage.
3. Seed disinfection. Dip with 40% formaldehyde 200 times for 30 minutes, then rinse dry, sow, or seed with 50% thiram or 40% acesulfame with a seed weight of 0.3%.
4. Control underground pests in time. The root mites and cockroaches were controlled by spraying with 80% dichlorvos emulsifiable concentrate 1000 times, and the larvae were treated with 48% chlorpyrifos emulsifiable concentrate 400-500 ml/mu.
5. Chemical control. Before harvesting, 75% chlorothalonil WP 600 times solution, or 70% mancozeb WP 500 times solution, 40% chlorpyrifos WP 400 times solution can be used for spray control.
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