How to Control Stevia Blight

Spot blotch is the primary disease in the production of stevia. With the extension of the planting period, the disease has been aggravated in recent years, which seriously restricts the increase of yield and quality of stevia. In the early stage of the disease, Stevia leaf spotted brown spots on the leaves, then expanded into spots or near-circular spots, and multiple dark spots were generated on the later stage lesions. Gradually spreading to upper leaves, leading to early deciduous.

● The characteristics of the disease

First, the area is large, and almost all the fields where Stevia is planted have varying degrees of pathogenesis. The second is the long-term hazard cycle, Stevia can be the incidence of the whole growth period. In the autumn cuttings, the pathogens can enter the seedbed and spread the damage through the diseased leaves on the cutting seedlings. The onset of seedlings is mild during the cold season in winter and spring. After the spring planting, the temperature becomes higher and the rainwater increases, and the disease spreads from June to July. Hazardous peak period. Third, there is a difference in the degree of disease among breeds.

● Prevention and management

Prevention of Stevia Blight, (1) rotation for crops: seedbeds should be carefully sited to reduce the spread of bacteria with seedling soil, try to choose disease-free cuttings. When conditions permit, Daejeon will implement a dry crop rotation. (2) Strengthen field management: Deeply turn over the soil, water mainly around the rhizosphere, do not flood with water, and promptly ventilate, reduce humidity, and remove the sick. (3) Chemical control: When the climate is suitable, the application of pesticides should be promoted in advance, and medication should be administered continuously in the field after sporadic illness. Some varieties of stevia are sensitive to mancozeb, thiophanate-methyl, and other drugs. They must be tested in small areas before use, and they can be used after determining safety.

Perennial herbs, thin rhizomes.Stem, upright, weak, 20-50 cm tall, 0.6 1 mm in diameter, often with section 2, the top section is located at stem base 1/4.Leaf sheath is flabby, smooth, longer than or upper shorter than internodes;Ligule transparent membranous, apex rounded or serrulate, 1-1.5 mm long;Blade erect, flat, 1.5-10 cm long, short stem, 1-3 mm wide, slightly rough, green or gray-green, tiller blades for up to 20 cm.Panicle narrow, linear, or during the flowering, 5-15 cm long, 0.5 3 cm wide, green, each with 2-5 slender branches, main branch for up to 4 cm, erect or sometimes rise;Spikelets handle bar, 1-2 mm long, 1.8 2 mm long; spikeletsThe first glume slightly longer than the second glume, apex acute, smooth, slightly rough ridge;No lemma awn, 1.2 1.5 mm long, with obvious veins 5, apex obtuse, base disk glabrous;Palea ovate, ca. 0.3 mm long;Anthers small, 0.3 0.4 mm long.And 4 to 7 months.

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