Introduction to the causes, symptoms and control methods of garlic leaf blight

Garlic leaf blight is a common disease in the process of garlic planting, especially in the open field, which is a nightmare for growers. Because garlic leaf blight will not only lead to poor quality of garlic, but also reduce production. Let's take a look at the causes, symptoms and control methods of garlic leaf blight.

I. the cause of garlic leaf blight

Garlic leaf blight is caused by Pleospora herbarum (Pers.ex Fr.) Caused by Rabenk infection. The pathogen overwintered mainly with the mycelium or ascomycetes in the soil, and the ascospores produced in the next year caused the initial infection, and then the conidia were re-infected with airflow and raindrop splash. After the emergence of autumn sowing garlic, the conidia produced on the diseased body spread with the airflow and raindrop splash and landed on the garlic leaves, causing infection.

The pathogen has strong adaptability to temperature, but needs higher humidity. Rainfall and high humidity in the field are the necessary conditions for the epidemic of the disease. The susceptible growth period of garlic is in the adult stage.

Generally, the disease is serious in the fields with low-lying terrain, poor drainage, partial application of nitrogen fertilizer, mixed cropping of onions and garlic vegetables, plant injury, thin plant growth and continuous cropping. The disease is serious in foggy and rainy years.

Symptoms of garlic leaf blight

Garlic leaf blight mainly harms leaves, leaf sheaths and bolting stems, and mainly occurs in leaves. After infection, the leaves showed four types of disease, namely, sharp blight type, stripe type, purple spot type and white spot type. When the disease is serious, the disease spot on the leaf can extend through the leaf node to the leaf sheath, making the leaf sheath withered and yellow. When the field is wet, the surface of the disease spot produces brown to black mildew layer. The lower leaves of the sharp withered type initially showed white round spots, and after the gradual expansion, the leaf tip became dark brown necrotic, with faint purple-brown twill on both sides. The stripe pattern mainly occurred in the middle and lower leaves. The leaves are infected, resulting in brown stripes throughout the leaves, developing along the middle ribs or on one side of the leaves. The streak type can be seen in the whole growth period, which is the main type of disease spot in the field. The leaves are damaged, the disease spots are oval or irregular, the central color is dark brown, the edges are light brown, and there are withered yellow necrotic lines at both ends, which can make the leaves withered and yellow after spreading. At the white type bolting stage, the upper leaves appeared dense round, oval white small disease spots, and the edge was obvious. Some leukoplakia develop into purple spots in the later stage.

III. Control methods of garlic leaf blight

1. Clean the countryside. After the garlic is harvested, the disease and debris in the field should be removed in time to reduce the number of bacteria overwintering.

2. Implement crop rotation. Try to avoid continuous cropping or mixed cropping with onion crops in garlic fields, and advocate rotation with wheat, corn, legumes or melons.

3. Strengthen the field management. Fine soil preparation, reasonable close planting, adequate base fertilizer, increasing phosphorus and potassium fertilizer, avoiding flood irrigation and timely drainage after rain.

4. Seed dressing with chemicals. Before sowing garlic, mix the seeds with 50% carbendazim wettable powder with 0.3% weight of garlic seeds.

Chemical control. The early stage of disease in the field You can choose 80% mancozeb wettable powder, 75% chlorothalonil wettable powder, 25% pyrimethrin suspension 1000 times, 10% difenoconazole water dispersible granules 1500 times, 2.5% phthalonitrile suspension 1200 times, 64% oxidizing manganese zinc wettable powder 1200 times, 50% promethrin wettable powder 1000 times, 50% imipramine wettable powder 1000 times, 50% carbendazim wettable powder 1000 times liquid and so on. Every 7: 10