Lettuce, also known as lettuce, is a plant of the genus Compositae, annual or biennial herb. He is now the most common ingredient used by friends when they eat grilled meat or hot pot.
Lettuce stems and leaves contain lettuce, bitter taste, high temperature, drought, bitter taste, can enhance gastric juice, stimulate digestion, increase appetite, and has analgesic and hypnotic effects. Today Xiao Bian came to tell everyone about the identification and prevention of several major diseases in the process of lettuce cultivation.
1, lettuce downy mildew
Hazardous symptoms The disease begins with the old leaves of the lower part of the plant. A pale yellow spot with yellowish water spots appears on the leaf surface at the beginning of the disease. After the enlargement, the veins are limited to a polygonal or irregular yellow-brown lesion.
On the back of the leaf, a white frosty mold layer grows on the back. The late lesions died, turning brown and connected to pieces, causing the entire leaves to dry.
Pathogenic conditions The pathogens spread with the aid of wind and rain and insects, suitable temperature 16 ~ 24 °C, relative humidity 70 ~ 80%, rain, fog, dew, early sowing, too dense planting, too much watering, or drainage is not easy Onset. September to mid-November is an epidemic.
Prevention
1 Strengthen the cultivation and management, timely sowing, reasonable close planting, cultivation of deep sorghum sorghum, timely ditch drainage, increase the application of available phosphorus and potassium fertilizer, and promote plant growth robust.
2 Chemical control: spraying at the beginning of onset, interval between 7 and 10 days, continuous spray control 2 or 3 times.
The agent can use 78% Cobo WP 500-600 times; 80% spray WP 500-800 times; 58% Lei Duomi Mn Zn wettable powder 600 times; 75% chlorothalonil wettable Powder 700 times; 72% Kelu wettable powder 800 times.
2. Lettuce Sclerotinia
Symptoms of Lettuce Sclerotinia Disease The disease is a fungal disease that occurs at the base of the stem near the ground.
At the early stage of disease, the diseased part was water-stained and quickly spread to the upper part of the stem, petiole and roots. The diseased tissue was soft rot, and the surface was densely covered with white cotton floc, which gradually turned into black smear sclerotia. The upper leaves of the diseased plant rapidly wilted and died.
The optimal temperature for disease onset is 10~20°C. At 80% relative humidity, the disease became severe. Humidity is less than 70%, the disease is significantly reduced, and high humidity is conducive to disease. In addition, it has been cultivated too densely, and it has been seriously affected by low light transmission conditions and poor drainage.
Prevention
1 Selection of disease-resistant varieties: For example, Wendeng No. 2 and lettuce red and other reddish varieties are more resistant to disease. Strong seedlings with soil colonization, seedling age 6-8 leaf stage better colonization. Can be used for nutrition seedlings or nutritious soil blocks nursery, transplanting with soil, improve seedling rate and disease resistance.
2 Chemical control: In the initial stage of onset, spray 50% sclerotia net or 50% of Nongliling 1000 times solution, or thiophanate-methyl 800 times solution, and control once every 7~10 days for 3~4 times.
3, lettuce soft rot
Symptoms of soft rot in lettuce The disease is a bacterial disease. Field plants usually start from the lotus period. The common symptom is that the condition of the plant progresses from the outside to the inside, and the first onset occurs at the junction between the base of the petiole and the rhizome on the outer leaf.
In the beginning, it became water-stained and the outer leaves were wilting at noon on a sunny day. It could be restored sooner or later or on rainy days. After a few days, the outer leaves were flat on the ground and no longer recovered.
The diseased leaves bleed on the ground to reveal the heart and leaves, the petioles, base of the stem, and pupa of the heart tissue are rotted, filled with white and yellow-brown viscous material, odor overflowing, the base of the stem turning brown and rot, accompanied by foul odor.
Another symptom is that the condition of the plant progresses from the inside to the outside, that is, the pathogen first begins to invade from the base of the cauliflower, causing the disease. The plant grows normally, and the heart leaves gradually rot outward and develops, filled with a yellow viscous liquid, and the diseased plant is pulled out immediately. Hurts and odors when humidity is high.
Disease conditions The pathogens are transmitted by rainwater, irrigation water, fertilizers, and insects. The disease temperature is 25~30°C, and the average sowing time is too early. Continuous disease and low-lying disease are heavy. It is generally popular from mid-October to late November.
Prevention
1 Pay attention to draining drains immediately after rain or irrigation. Combined with disease prevention and application of 0.2% potassium dihydrogen phosphate, boron fertilizer and other foliar spray, improve plant resistance.
2 Chemical control: Use Daisen ammonium water 1000 times solution, 72% agricultural chain penicillin or neophytin 4000 times solution, or 47% kill powder 500 times, or 47% Garrett powder 800 times or DTM (chlorotoluene) powder 600 times, once every 5 to 7 days, 3 to 4 times in a row.
4, lettuce black spot
Symptoms of the disease The typical symptoms of the disease is the formation of round or near-round brown plaques on the leaves of 3 to 15 mm in diameter with a concentric ring pattern. When wet, the back of the lesion can produce black mold.
Conditions of the disease The disease is spread by wind and rain, warm and rainy, with long dew condensation time, lack of fertility, and weak plant disease.
Prevention
1 to strengthen the cultivation and management, increase phosphorus and potassium fertilizers. Rotation is carried out to remove old, sick and leaves in time.
2 Chemical control should be used at the beginning of the disease, 50% Pouhai solid wettable powder 1500 times, 40% captan WP 400 times, 70% phosphine manganese zinc wettable powder 500 times, 75% chlorothalonil Wettable powder 600 times liquid and other rotation, 7 days, a total of 2 or 3 times.
5, lettuce gray mold
Hazardous symptoms: The diseased part of the seedling stage was watery and rotted, with a layer of gray mildew, and the incidence of adult plants mostly started from the leaf near the ground. It was water-stained at the beginning and rapidly expanded afterwards. It was yellow-brown.
Incidence of disease onset temperature of 20 ~ 25 °C, with the aid of airflow. Invasion and re-infestation occurs from invasive or debilitating tissue on the plant. Relative humidity more than 93%, the incidence of heavy.
Prevention
1 Dispose of the diseased plants in time after harvest, concentrate burned or buried deeply, and reduce the source of bacteria.
2 Protected areas should enhance ventilation, reduce humidity, prevent condensation on the foliage, fully apply organic fertilizers, and increase application of phosphorus and potassium fertilizers.
(3) Chemical control, onset of disease, and use of 250 grams per acre with 250 grams of smoke per acre in the evening smoke control, or with 40% Shijiale 1200 times match solution, or 50% carbendazim WP spray, every 7 days Once, 3 to 4 times in a row.
6, Lettuce virus disease hazards Symptoms of damage caused by plant dwarf, deformity, uneven shade of leaves, yellow and green, leaf shrinking curl or uneven, often many small brown spots, new leaves appear Mingmai or mosaic, old leaves brown Necrotic spot. The undeveloped root system of the diseased plant seriously affects the growth and development.
The pathogenetic conditions of the disease are mainly transmitted by locusts and contact infections. They are usually from mid-August to mid-September, and from mid-September to early-October.
The seedling stage, especially before the 7th leaf, is a susceptible period. The earlier the infection, the heavier the disease. Early sowing, more locusts, extensive management, dry soil, lack of water, lack of fat land mass.
Prevention
1 sowing, escape the heat and locust season.
2 Chemical control: Flood control at seedling stage is very important. Controlling aphids can use 20% Kangfuduo or imidacloprid or 50% Kangweiwei 2000 times.
Virus disease prevention and treatment can use one thousandth of potassium permanganate or 83 increasing agent 100 times liquid or plant disease spirit (II) 1000 times liquid.
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