Lettuce, including head lettuce and leaf lettuce, likes to grow in a neutral soil environment with cool and humid, fertile soil and loose texture. It is cold-resistant and disease-resistant. Toby generally doesn't feel sick when the data management is relatively normal. When management is backward, or in an unfavorable growth environment, you will feel even more disgusting.

Common diseases on lettuce include powdery mildew, Sclerotinia sclerotiorum, leaf spot and chilling injury. The main pests are aphids, beetles, silkworms, slugs and Pieris rapae (larvae).

Starting from the basal leaves, pale yellow source spots appear on the leaves of raw vegetables. When the air is humid, a layer of white frosty fungi will grow on the back of the leaves, sometimes on the front of the back leaves. Tremella layer is serious, the lesions fuse with each other, and the leaves wither and die. At this time, powdery mildew has reached the peak season.

The occurrence of downy mildew is related to factors such as high humidity in the field, too dense planting, too much irrigation and poor drainage, which may lead to downy mildew of lettuce.

Selection of fungicide for lettuce powdery mildew: 45% tretinoin (a compound of tretinoin and aniline), 800~I200 times water dispersant, or 45% fluorine? Pyrazole (flumorph and pyrazole) water dispersant 1200~ 1500 times, or 33%.

This is also a common shortcoming of lettuce. When lettuce grows, most of it spreads from the roots to the leaves. It is not easy to observe in humid air environment, and only brown or beige wet spots are formed on lettuce leaves. It can be observed with naked eyes that when the disease gets worse, lettuce leaves have deteriorated and started to rot.

Over time, if the whole lettuce rots and dies, the diseased man's tissue will grow a sclerotia like mouse excrement, which is the most obvious difference between this disease and other diseases.

The occurrence of lettuce Sclerotinia sclerotiorum is also related to high humidity, low temperature and weakened plant stress resistance in the field. Of course, if the humidity is high, there may be concentrated precipitation or excessive water accumulation in the near future, or it may be related to water accumulation in the field. Moreover, if the growth is vigorous, the nutrition is vigorous, and the resistance to nitrogen fertilizer decreases, lettuce diseases may occur.

At the initial stage of the disease, 55% Li Jun urea (the binary compound of Li Jun urea and mold stomach) was used as 800~ 1200 times solution, or 800 ~ 10 times solution was added with 40% wet powder of sclerotium, or 70% thiophanate-methyl moisturizing powder was added with 40% wet powder of sclerotium to prepare 800 ~/.

In addition, the rapid chilling injury of lettuce mainly occurs in seedling stage, but not in growth stage. When leaf spot, downy mildew and Sclerotinia sclerotiorum are injected at the same time, comprehensive control can be implemented without using drugs alone.