Comprehensive Control Methods and Technical Key Points for Garlic Leaf Blight
Garlic Allium sativum L. (Garlic) belongs to the Liliaceae family, Allium genus, and its bulb is used as medicine. Harvest in spring and summer, tie into bundles, hang in a ventilated place, and dry in the shade for later use. When the leaves wither in June, dig up, remove mud and sand, dry in a ventilated place or bake until the outer skin is dry. Garlic is flat-spherical or short-conical, with a grayish-white or light brown membranous skin outside. After peeling off the scale leaves, there are 6-10 garlic cloves inside, arranged in a ring around the flower stem, with a disc-shaped stem base bearing numerous fibrous roots. Each garlic clove is wrapped in a thin membrane; peeling off the membrane reveals white, thick, juicy scales. It has a strong garlic odor and a pungent taste.
Plant Morphology of Garlic
Perennial herb, with a strong garlic odor. Bulb large, with 6-10 cloves, wrapped in a grayish-white or light purple membranous scale covering. Leaves basal, solid, flat, linear-lanceolate, about 2.5 cm wide, with a sheath-like base. Flower stem erect, about 60 cm tall; spathe with a long beak, 7-10 cm long; umbel small and dense, with 1-3 bracts, 8-10 cm long, membranous, light green; flowers small, often mixed with pale red bulbils, 4 mm long, or completely without bulbils; pedicels slender, longer than the flowers; perianth 6, pink, elliptic-lanceolate; stamens 6, white, anthers exserted; pistil 1, style exserted, white, ovary superior, long elliptic-ovate, apex concave, 3-locular. Capsule, dehiscing by 1 locule. Seeds black. Flowering in summer.
Comprehensive Control of Garlic Leaf Blight
Garlic leaf blight is one of the common diseases on garlic, occurring to varying degrees in all vegetable-growing areas, mainly harming open-field cultivated garlic. In years with frequent rainfall and high precipitation during the garlic growing period, the disease is severe. When the disease is severe, it often causes diseased leaves to wither, premature plant decline, reduced garlic bulb yield, and moldy garlic scapes, directly affecting yield.
Disease Characteristics of Garlic Leaf Blight
Initially appearing as small white round spots, later expanding into irregular or elliptical grayish-white or grayish-brown lesions, with black moldy growth on the upper part, and many small black particles scattered on them. When the damage is severe, the whole plant does not bolt.
Disease Pattern of Garlic Leaf Blight
This disease is caused by infection by the fungus Pleospora herbarum (Pers.ex Fr.) Rabenk, an ascomycete in the subphylum Ascomycota. In spring-sown garlic cultivation areas, the pathogen mainly overwinters in the soil as mycelium or perithecia with diseased residues, and the following year produces ascospores causing primary infection; later, conidia produced in diseased parts are spread by airflow and raindrop splashing for secondary infection. After autumn-sown garlic emerges, conidia produced on diseased residues are spread by airflow and raindrop splashing, landing on garlic leaves, causing infection and disease. This fungus is a weak parasite, often occurring mixed with downy mildew or purple blotch. The pathogen has strong adaptability to temperature but requires relatively high humidity. Rainfall and high field humidity are necessary conditions for disease epidemics. In Zhejiang and the middle and lower reaches of the Yangtze River, the main peak period of garlic leaf blight is during the plum rain season. The susceptible growth stage of garlic is the adult plant stage. Generally, disease is severe in fields that are low-lying, poorly drained, with excessive nitrogen fertilizer application, mixed cultivation with onion and garlic vegetables, injured plants, weak plant growth, and continuous cropping. In years with plum rain season or autumn with much fog and rain, the disease is severe.
Comprehensive Control Methods for Garlic Leaf Blight:
1. Seed disinfection. Before sowing, soak seeds in warm water at 50°C for 30 minutes or dress seeds with 0.5% amobam or thiram for seed disinfection. 2. Soil treatment: For soil disinfection, mix thiram and quintozene at 1:1, 500-750 g per mu, mix with 400 times dry soil, and broadcast on the soil surface before plowing.
2. Open ditches for drainage. The sowing period of early-maturing garlic is September-October, which is in the late rainy season, when the soil is moist, prone to seed rot and seedling death and inducing the occurrence of garlic leaf blight. Especially in rice stubble fields, ditches should be opened for drainage to reduce soil moisture, which is beneficial for emergence and reduces diseases, pests, and weeds.
3. Increase application of farmyard manure. Garlic has few fibrous roots and weak absorption capacity, so it needs loose soil and rich organic matter. It is advocated to mainly use farmyard manure and increase the application of phosphorus and potassium fertilizers. By improving soil fertility, the disease resistance of plants is enhanced.
4. Chemical control. In the early stage of disease, 70% mancozeb at 200 g per mu can be used for spraying, and another control application after 7-10 days; in the peak period of disease, 50% iprodione wettable powder at 1500 times dilution or prochloraz at 50 g per mu can be used for control, and broad-spectrum pesticides such as chlorothalonil and mancozeb can also be used for control.