Principle and control of soft rot of lettuce

Lettuce is the common name of leaf lettuce, which belongs to the genus lettuce of Compositae. It is an annual or biennial herbaceous crop. It is also a popular vegetable in Europe and the United States. In recent years, the cultivation area has expanded rapidly, and lettuce has also entered the table of ordinary people from hotels and restaurants.

Growth habits of lettuce

Lettuce likes cold environment and is neither cold-resistant nor heat-tolerant. The suitable temperature for growth is 15 ℃-20 ℃ and the growth period is 90-100d. The seeds are tolerant to low temperature and can germinate at 4 ℃. The optimum temperature for germination was 18-22 ℃, and there was almost no germination when it was higher than 30 ℃. During the period of plant growth, it likes cool climate, and 15-20 ℃ is the most suitable for growth, with high yield and good quality, and continuously higher than 25 ℃, with poor growth, thick and old leaves and slightly bitter taste. However, the cold tolerance is also quite strong, and 0 ℃ or even short-term subzero low temperature does not hinder the growth. Lettuce has developed root system, waxy leaves and strong drought tolerance, but it has high yield and good quality when cultivated on fertile and humid soil. The suitable pH value of soil is 5.8-6.6.

Principle and control of soft rot of lettuce

Symptoms of lettuce soft rot:

The disease often occurs in the middle and late growth period or ball receiving stage of lettuce, mostly from the wound at the base of the plant, the disease begins to invade and translucent, and then expands into an irregular shape, waterlogged shape, full of light grayish brown sticky matter, and releases a foul smell. With the development of the disease, the disease extends rapidly upward, making the vegetables rot in autumn. Sometimes, the pathogen also begins to rot from the outer leaf margin and the top of the leaf ball.

The incidence regularity of soft rot of lettuce:

The pathogen overwintered mainly on diseased plants and diseased residues in soil fertilizer, or continued to harm other vegetables. Invaded by the wounds and physiological cracks of the plant by watering, fertilizing or spreading by insects. The growth temperature of the pathogen was 4-39 ℃, and the optimum temperature was 25-30 ℃. The disease is serious when there are many wounds caused by improper management of water and fertilizer in the field, a large number of pests or agricultural operations.

Control methods of soft rot of lettuce:

1. Agricultural prevention and control: rattan stubble as early as possible, even if the soil is more turned over, so that the residues of the previous crops will fully rot and decompose in front of the plants; the seriously diseased land shall be planted with high ridges or high beds; the farm manure with sufficient rotten heat shall be applied; planting in the visual period to avoid the high temperature and rainy season; sunshade net or non-woven fabric for sunshade and rain protection in the high temperature season; pay attention to drainage at any time after watering or rainfall to avoid stagnant water in the field; remove the diseased plants in time when found.

2. Drug prevention: at the initial stage of the disease, 50% wettable powder can be used to prevent and cure the disease, or 5000 times of neophytomycin and agricultural streptomycin should be sprayed every 7-10 days for 2-3 times.