Control measures of lettuce downy mildew in field

lettuce (scientific name: Lactuca sativa L.var. angustanaIrish.）Any of several varieties of lettuce, an annual herb, that form succulent tender stems. Alias stem lettuce, lettuce shoots, green shoots, cabbage.

Morphological characteristics of lettuce

The stem looks like a circle, like a bamboo shoot. Straight roots, most lateral roots after transplantation, shallow and dense, mainly distributed in 20-30cm soil layer. Stems shortened. Leaves alternate, lanceolate or long oval, etc., color light green, green, dark green or purple, leaf spreading or ruffled, entire margin or notch. The shortened stem gradually elongates and thickens with the growth of the plant. After the flower bud differentiation at the stem end, the stem thickens and grows at the same time as the flower stem elongates, forming a rod-shaped fleshy tender stem. Light green, emerald green or yellowish green. Panicle head, pale yellow flowers, each inflorescence has about 20 flowers, self-pollinated, sometimes cross-pollinated. Achene, black-brown or silvery-white, with crested hairs.

Dietotherapy of lettuce

Open Shu Li, eliminate the accumulation of gas: lettuce taste fresh and slightly bitter, can stimulate the secretion of digestive enzymes, enhance appetite. Its milky serous fluid can enhance the secretion of gastric juice, digestive glands and bile, thus promoting the function of various digestive organs, especially beneficial to patients with weakened digestive function, reduced acidity in digestive tract and constipation;

Diuretic milk: lettuce potassium content is much higher than sodium content, conducive to the body's water electrolyte balance, promote urination and milk secretion. For hypertension, edema, heart disease patients have a certain dietotherapy effect;

Strong body, anti-cancer and anti-cancer: lettuce contains a variety of vitamins and minerals, has the role of regulating nervous system function, its organic content is rich in iron that can be absorbed by the human body, which is very beneficial to patients with iron deficiency anemia. The hot water extract of lettuce has a high inhibition rate on some cancer cells, so it can be used to prevent cancer and cancer;

Wide bowel laxative: lettuce contains a lot of plant cellulose, can promote intestinal wall peristalsis, Tongli digestive tract, help stool excretion, can be used to treat various constipation.

Field control measures of lettuce downy mildew

In recent years, with the expansion of lettuce planting area, lettuce downy mildew has become a serious disease in spring and autumn cultivation, which seriously affects the quality and yield of lettuce and reduces economic benefits.

Field symptoms of lettuce downy mildew:

The disease mainly damages leaves. The disease first occurs on the leaves near the ground, then gradually spreads upward, developing inward from the outer leaves of the plant. At first, the leaves produce pale yellow spots, which are restricted by the veins to be polygonal or irregular. When the disease is seriously ill, the spots die and connect into pieces, resulting in the whole leaves turning yellow and withered, seriously affecting the growth of the plant. The typical symptom of the disease is a white frosty mold layer growing on the back of the leaf when wet.

Conditions for the occurrence of downy mildew of lettuce: the pathogen overwinters in the seed with mycelium or in the soil with ospores. The disease spreads by wind and rain, invades from stomata of plants, the suitable temperature for infection is 15-17℃, the disease is more serious in rainy spring and autumn, planting is too dense, the field humidity is high, watering is too much, poor drainage is easy to occur.

Effective control measures for lettuce downy mildew in the field:

Selection of disease-resistant varieties: general tip leaf lettuce is more disease-resistant than garden leaf lettuce. Such as white pointed leaves lettuce, etc.

Strict crop rotation, ridging cultivation.

Reasonable close planting, keep the field ventilated and transparent. Generally, the row spacing is 35-40 cm, the plant spacing is 25 cm, and about 6000 plants are planted per 667㎡.

Strengthen field management. Cultivate the plants in the field before closing the ridge, and increase the number of cultivation times at seedling stage. Watering more in early stage and less in late stage, reduce watering times after plant ridge sealing, reduce field humidity, prevent water accumulation in field, promote plant growth and inhibit pathogen development.

Timely observation, early detection of illness, timely cleaning of the countryside. Remove the diseased leaves in time, especially the old leaves at the lower part, to increase permeability.

Chemical control was adopted. 58% metalaxyl manganese zinc WP 500 times, 40% phytophthora WP 200 times, 72% antaisheng WP 700 times, alternate spraying, once every 7-10 days, continuous spraying 2-3 times, can effectively control lettuce downy mildew, improve lettuce yield and quality.