What symptom does lettuce gray mold have? How to prevent and cure?

Botrytis cinerea is a common disease in the process of lettuce planting. Once it occurs, it has a great impact on growers, affecting not only the quality but also the yield. What are the symptoms of lettuce gray mold? How to prevent and cure?

What are the symptoms of lettuce gray mold?

Botrytis cinerea of lettuce is mainly harmful to leaves, generally starting from the leaves near the ground, showing water-immersed, irregular spots at first, and then expanding brown, irregular spots of different shape and size. In a humid environment, the disease produces a gray or grayish-white mildew layer.

Botrytis cinerea can survive in the soil, on the plant, on the back wall of the greenhouse, on the post, on the hanging line, and spread to the plant through air flow, Rain Water, farming operation and so on. Once the conditions are suitable, it will germinate and infect rapidly.

The pathogen is easy to invade Botrytis cinerea from the wound and likes to be "sweet and tender". The most favorite infection sites are flowers, young fruits and fruits that change color to mature. The reason is that some secretions on the floral organ will stimulate the bacteria to multiply rapidly, and once there is a wound on the young epidermis or mature fruit, the bacteria will "follow" the juice from these parts.

The weather which is prone to outbreak of Botrytis cinerea at high humidity is an important reason that affects the occurrence rate of Botrytis cinerea. Botrytis cinerea prefers cooler temperatures (18-23 ℃) and high humidity (more than 85%), as well as weather with insufficient light. Therefore, gray mold is easy to break out when it snows or rains on cloudy days.

Second, how to prevent and cure grey mold of lettuce?

1. Agricultural prevention and control

Rational management of water and fertilizer, strengthening fitness cultivation, timely removal of snow on the roof and stagnant water outside after rain and snow.

Use plastic film hidden irrigation or drip irrigation to avoid flood irrigation, ventilation and humidity reduction in time after irrigation. Pruning and branching in time to improve the ventilation and light transmittance of the lower part of the plant. Timely pick the lower old leaves and diseased flowers, diseased fruits, diseased branches and leaves, take them out of the shed and concentrate on heap or deep burial, so as to reduce the source of infection. Regulate the temperature and humidity in the shed to create environmental conditions that are not conducive to the incidence of Botrytis cinerea. On a sunny day in winter, let out for 30 minutes in the morning, reduce the humidity to less than 75%, then close the shed tightly, let out a light breeze when the temperature in the shed rises to 30 ℃, control the temperature at 28032 ℃, and increase the ventilation volume in the afternoon to control the humidity below 70%.

2. Biological control

Use biological pesticides to prevent and control Botrytis cinerea. In the early stage of the outbreak of Botrytis cinerea in protected vegetables, 125g / mu of polyantimycin WP, 100g / mu of 300m CFU/ KKT WP, or 45g / g of 100 billion spores / g Bacillus subtilis WP, or 125g / g of Trichoderma WP, or 100kg 120ml of 1% Shenazinmycin suspension and 20kg of water were sprayed evenly.

3. Chemical control

(1) smoke method. At the initial stage of the disease, 175 200 grams of 20% Pythium chlorothalonil per mu or 250 grams of 300 grams of 15% chlorothalonil smoke remover were placed in 4-5 places in the shed, lit in the evening, ventilated the next morning, and fumigated again every 7-10 days.

(2) spray method. At the initial stage of the disease, 25% Pythium thiram wettable powder 60g / mu, or 50% promethopril suspension 75ml 100ml, or 50% isocarbamide suspension 50ml 100ml, or 22.5% pyrimethrin suspension 26ml 36ml, or 20% pyrimidine suspension 125ml 180ml, or 30% pyrimidinamide suspension 67ml 83ml, or 30% pyrimidine tebuconazole suspension 40ml 60ml Or 43% fluromycin oximate suspension 30g 45ml, or 30% trimethoprim suspension 9ml 12ml, or 30% acetonitrile suspension 45ml 60ml, or 50% fluidixamide water dispersible granule 27g 35g, or 50% carbendan wettable powder 155g 190g, add water 20kg 30kg uniform spray. Can not spray large amount of water, after the medicine should be timely ventilation to reduce humidity, to prevent the increase of humidity in the shed, to promote the occurrence of diseases. Pay attention to the safe use of drugs, adhere to rotation and alternate use of drugs. Pick after the pesticide safety interval to ensure that the pesticide residue does not exceed the standard.