Integrated control techniques of Sclerotinia sclerotiorum of lettuce

Lettuce, also known as lettuce, Asteraceae lettuce species can form a variety of fleshy tender stems, herbaceous plants in 2012. Alias stem lettuce, lettuce bamboo shoots, green shoots, lettuce. Delivery period: from January to April. It is native to Central or North China. Lettuce has strong adaptability and can be cultivated in spring and autumn or overwintering, mainly in spring and harvested in summer.

Introduction of lettuce varieties

First, purple bamboo shoots with pointed leaves. The height of the plant is about 40 cm and the degree of development is about 55 cm. The leaves are lanceolate, about 42 cm long and 55 cm wide. The leaves are lanceolate, about 42 cm long and 14 cm wide. Bamboo shoots are long rod-shaped, 51 cm long, 6 cm in horizontal diameter, green and white skin and meat, crisp meat, less moisture and good quality. The single bamboo shoot weighs about 1000 grams, which is more resistant to downy mildew. It is suitable for autumn sowing and overwintering cultivation, and it is a medium-ripe variety.

Second, willow bamboo shoots. The plant height is 40-60 cm, the degree of development is 45 cm, and the growth potential is strong. Leaves erect, light green, lanceolate, like willow leaves. The leaf surface has shallow wrinkles, with wax powder, and the leaf margin is shallowly wavy. Bamboo shoots show a long stick shape, 30-35 cm long, 5 cm in transverse diameter, green and white outer skin, light green meat, crisp and tender texture and good quality. The weight of a single bamboo shoot is about 500g and the yield is 2000-3000 kg per mu. Cold-resistant and heat-resistant, bolting late, it is a mid-late maturing variety. It is suitable for open field cultivation in autumn.

Third, wild goose Ling bamboo shoots. The plant height is about 60 cm, the degree of development is 40 cm, and the growth potential is strong. The leaves are lanceolate, light green and wrinkled. Bamboo shoots are long stick-shaped, 24 cm long, 5.5 cm in horizontal diameter, green and white skin, light green meat, thin skin, crisp, sweet taste and much moisture. The weight of a single bamboo shoot is about 500g and the yield is 3000-3500 kg per mu. Cold-resistant and heat-resistant, strong disease resistance. , is a medium-ripe variety. It is suitable for cultivation in spring and autumn.

Sclerotinia sclerotiorum is one of the main diseases of lettuce, which seriously affects the planting benefit of lettuce, so how to carry out comprehensive control of Sclerotinia sclerotiorum of lettuce?

Symptoms of Sclerotinia sclerotiorum in lettuce

The whole growth period of the plant can be harmed by Sclerotinia sclerotiorum. In the middle and later stage, there is much shade, poor ventilation and permeability, high humidity and more serious harm. The stem, petiole or leaf in the lower part of the plant generally occurs first, and after the stem is damaged, the aboveground part wilts and finally dies. The petiole and leaves are damaged, and the symptoms are the same as those of the stem. At the initial stage, the disease site was flooded and light brown, and the tissue softened and rotted gradually, but there was no odor. Under wet conditions, the disease produced dense white cotton-like hyphae, and in the later stage, the mycelium interwoven into white particles and produced yellow water droplets. when the white particles grow up, they become black-brown mouse fecal sclerotia.

Pathogen of Sclerotinia sclerotiorum of lettuce

Sclerotinia sclerotiorum of lettuce is caused by pathogenic fungi of subphylum sclerotiorum, and its vegetative body is septate hyphae. The sclerotia germinated and grew into a fruiting disk with a stalk at the bottom, about 2 Mel 8 mm in diameter. The seed is stick-shaped, colorless, with a size of 91m ~ 125 × 6 ~ 9 μ m and contains 8 sporospores. The conidia are oval, monospore, colorless, with a size of 9mur14 × 3Mel 6 microns, arranged neatly in the capsule, and the sporospore is its sexual reproductive organ.

Transmission pathway and disease conditions of Sclerotinia sclerotiorum in lettuce

The sclerotia overwintered in the soil and formed a seed capsule under suitable conditions, emitting spores, which spread through wind and rain and became the source of primary infection. Infection in the field usually comes into contact with healthy plants through diseased tissue, and the hyphae spread directly.

The optimum temperature for sclerotia germination was about 15 ℃. The temperature range of conidia germination is 0 ℃ 35 ℃, and the optimum temperature is 5 min 10 min. The mycelium could grow at 30 ℃ and the optimum temperature was 20 ℃. Sclerotia can grow in an environment with a PH value of 1.68mur10. A relative humidity higher than 85% is beneficial to spore germination and mycelium growth, while less than 70% is mild. Therefore, when the field temperature is about 20 ℃ and the relative humidity is higher than 85%, it will lead to the epidemic of the disease.

Integrated control of Sclerotinia sclerotiorum of lettuce

Agricultural prevention and control

The main results are as follows: 1) rotation with Liliaceae vegetables has been carried out for more than 3 years.

2) the disinfection of soil can not be carried out in the diseased land where rotation can be carried out. After pulling seedlings in the protected field in spring, the high temperature in three summers can be used for soil disinfection. The method is: first clean out of the garden, take the diseased body out of the field for deep burial or burning; apply lime 50ml 100kg every 666.7 square meters, crushed rice straw or wheat taro 500kg, evenly apply to the surface; turn 60 cm deep and raise a high ridge of 30cm; irrigation in the furrow requires that there is always water in the ditch during the treatment, so it should be watered constantly; cover the plastic film and cover it strictly all around The closed greenhouse for 20 days can make the soil 20 centimeters deep and the soil temperature reaches more than 50 ℃ (the highest temperature), which can kill sclerotia.

3) choose disease-free seeds to keep seeds from disease-free areas. Seeds with sclerotia can be selected with 10% salt water, sclerotia are removed, and then rinse repeatedly with clean water before sowing.

4) cultivation, control and cultivation of disease-free seedlings; covering black plastic film can prevent the ascus from being unearthed; apply sufficient organic fertilizer and increase phosphorus and potassium fertilizer; strengthen ventilation and reduce humidity; clean the countryside in time, take the diseased leaves and diseased plants out of the field and bury them deeply or burn them (including the timely eradication of unearthed ascomycetes).

Chemical pesticide control: after pollution-free pesticide control, 3.5% thiabendazole (Teketol) smoke agent can be used for fumigation in the evening, once every 7 days, continuous fumigation 3-4 times (250g per 666.7 square meters).

1. A few days before the seedling bed is sprayed, the seedlings of the seedling bed can be sprayed with 20% triadimefon (triadimefon) EC 4000 li 5000 times.

2. After spraying and colonizing the diseased field, at the initial stage of the disease, 50% sulfamethoxazole wettable powder 1000m 1200 times liquid, or 50% carbendazim wettable powder 1000 times liquid, or 40% sclerotia net wettable powder 1000-1200 times liquid, or 50% isocarbamide (promethazin) wettable powder 1000 times 1200 times, or 50% carbendazim wettable powder 600 times 800 times, focusing on the base of stems and leaves, once every 7 days, for 4 times in a row.

3. Before or at the initial stage of the disease, 10% Sukeling smoke agent or 15% curd smoke agent can be used, 250g per 666.7 square meters, fumigation in a closed shed in the evening, once every 7 days, and 4 times in a row.

4. Dust prevention and control before or at the initial stage of the disease, 6.5% methylmethalin dust, or 5% chlorpromazine dust, or 5% lidocaine dust can be used, 1000 grams every 666.7 square meters, sprayed in the morning or evening, with a powder sprayer (no water), sprayed once every 7 days, 4 times in a row.