Main diseases and control of vegetables in soilless cultivation

At present, there are many ways of soilless cultivation in China, such as nutrient solution soilless cultivation, organic ecotype soilless cultivation, nutrient solution hydroponics and organic soilless cultivation. Leafy vegetables are the main vegetables, followed by fruit vegetables and melons. There are Chinese cabbage, Chinese cabbage, lettuce, cabbage, celery, leek, tomato, bell pepper, cucumber, melon, strawberry and so on.

Among several cultivation methods, ecological intelligent greenhouse hydroculture, organic ecological soilless cultivation and dynamic floating root hydroponic system have been adopted by farmers at present. Ecological intelligent greenhouse is based on ordinary glass greenhouse. The cultivation conditions and physical and chemical properties of nutrient solution, including temperature, light, carbon dioxide concentration and so on, needed for vegetable growth are regulated by microcomputer system to meet the needs of all kinds of vegetable growth to the maximum extent. The dynamic floating root hydrotillage system makes use of the flow of the nutrient solution in the irrigation and drainage process to make the plant root rise and fall with the nutrient solution in the depth of 4-8 cm, and fluctuate left and right at the same time, so that the upper root is exposed in the air layer so as to increase the dissolved oxygen. Its advantages are high yield, not affected by season, intensive cultivation, small land occupation, suitable for areas with poor soil quality or lack of water, effective use of water and fertilizer, suitable for mechanized cultivation and so on. However, it should be pointed out that soilless culture has its own ecosystem, and once germs or pests invade, diseases and pests expand rapidly, especially some water-borne pathogens will spread to all plants with the circulation of nutrient solution, causing root diseases.

Vegetable diseases in soilless culture are mainly divided into two categories: physiological diseases and infectious diseases. Physiological diseases, after using water tillage to cultivate vegetables for a period of time, a lot of unnecessary ions or toxins are accumulated in the nutrient solution, and plant disease caused by element deficiency will occur at the same time, which can be prevented as long as fresh nutrient solution is often replaced in production. In infectious diseases, leaf diseases are basically the same as open-field cultivation, but root diseases have become a prominent problem of soilless vegetables, especially the root rot caused by rot mold is difficult to control, so some soilless cultivation farms are abandoned.

I. characteristics of diseases in soilless cultivation

The diseases in soilless cultivation are slightly different from those in open field or ordinary protected cultivation. Characteristics of disease occurrence in soilless culture:

First, diseases are transmitted by seeds or seedlings.

The diseases transmitted by seeds can be divided into three types: fungal diseases, bacterial diseases and virus diseases. In fungal diseases, many vegetable seeds are invaded and infected by fungi during ripening, which become diseases transmitted by seeds; others are contaminated by seeds or seed coat in the process of seed harvesting, the bacteria will be introduced into the nutrient solution through the circulation of nutrient solution to cause secondary pollution, such as cucumber, melon vine blight, anthracnose, tomato Fusarium wilt and so on. Among the bacterial diseases, the canker of tomato and the bacterial corner spot of melons can be caused by the seeds entering the nutrient solution and polluting the cultivation bed.

In virus diseases, many viruses can be transmitted by seeds, such as melon green spot mosaic virus, melon gangrene mottle virus, tomato mosaic virus and so on.

Second, diseases are transmitted by air or surface pollution in facilities.

Many fungal or bacterial diseases are often transmitted by air and soil surface pollution into the nutrient solution, such as melon, cucumber powdery mildew, tomato powdery mildew are spores drifting into the cultivation bed. Muskmelon vine blight and Phytophthora are caused by pollution or dust floating to the surface of the plant. In addition, cucumber green spot mosaic virus can also spread the disease through contaminated soil.

The third is to spread diseases by water pollution.

In soilless cultivation, the source of nutrient solution is groundwater, and bacteria are easy to enter the nutrient solution in the process of water transportation, such as tomato bacterial wilt and cabbage and cabbage soft rot.

Fourth, tools spread diseases.

Such as eggplant fruits, melons virus diseases, bacterial diseases, often through pruning, branching, binding vines, harvesting tools or hands to spread. In addition, thrips, whiteflies and aphids that can enter the facility can also spread various viral diseases.

Fifth, the use of contaminated nutrient solution or nutrition pool can also spread the disease.

For example, after the occurrence of bacterial soft rot in the previous crop, the bacteria will remain, and after planting new vegetable seedlings, the bacteria can harm the new seedlings.

Second, the present situation of main diseases in soilless cultivation.

The main infectious diseases in soilless culture are tomato powdery mildew, cucumber, melon, watermelon rot, Phytophthora root rot, powdery mildew, downy mildew, vine blight, vine cut, sclerotiorum, virus, etc.; black rot, soft rot and virus disease of heading cabbage; bacterial spot of lettuce, bacterial rot and so on. Non-communicable diseases are mainly caused by element deficiency due to poor management in soilless cultivation. In addition, in soilless culture, green algae often compete with crops for nutrients, leading to the occurrence of element deficiency.

3. Control of main diseases in soilless cultivation.

In order to prevent and control the diseases occurred in soilless cultivation, we should carry out the three principles of eliminating diseases, avoiding diseases and utilizing diseases.

One is seed disinfection.

Seeds can be sterilized by dry heat, such as treating seeds with 70-72 ℃ for 3 days, soaking seeds with 53-55 ℃ warm soup for 20-30 minutes, or soaking seeds with 10-100 times hypochlorite solution for 60 minutes.

Second, nutrient trough and tool disinfection.

Disinfect nutrient troughs and tools with 75% alcohol or 50-100 times potassium permanganate solution to prevent the survival of pathogenic bacteria.

The third is the disinfection of shed and equipment.

Before planting, all plant remains should be removed inside and outside the greenhouse, and the ground should be covered with clean plastic film to isolate the soil. Space disinfection can evenly place 3-4 large bottles in the greenhouse, pour in potassium permanganate and formaldehyde, use 4 grams of potassium permanganate and 4 grams of formaldehyde per cubic meter of space, ventilate after 24 hours in the greenhouse, and then plant after the chemicals are volatilized. The disinfection of cultivation facilities and utensils can be soaked in 1000 times of neutral calcium hypochlorite or rinsed for 1-2 days. Disinfection used residue can be discharged to the greenhouse floor or the surrounding soil as environmental disinfection. After disinfection of facilities and appliances, rinse off the residue with clean water to prevent drug damage.

The fourth is the disinfection of nutrient solution.

The nutrient solution can be disinfected and sterilized by physical, chemical or fungicide treatment. Physical methods include filtration, ultraviolet sterilization, ultrasonic treatment, pasteurization, etc., while chemical methods include ozone treatment, surfactants and pesticides.

Fifth, the cleanliness and hygiene of the operators.

When entering or leaving the greenhouse or greenhouse, operators should first step on the foam mat soaked with disinfectant in the disinfection trough at the door. Choose 84 disinfectant or 0.3% bleach, add the disinfectant at least once a week, and warn the relevant personnel not to wash hands with nutrient solution in the pool.

4. Fungicides and methods commonly used in soilless cultivation

Commonly used fungicides are carbendazim, carbendazim, metalaxyl and so on.

1. Carbendazim. It is widely used in circulating hydroponic tomato. Generally, when the tomato root system grows from the seedling block, adding 20 mg (effective ingredient) to 1 liter of nutrient solution and applying it every 6 weeks can effectively control tomato blight and root diseases such as cucumber and melon.

2. Carbendazim. Adding 10 mg carbendazim to 1 liter of nutrient solution every 2 weeks can effectively control black rot, brown rot and vascular bundle diseases of hydroponic tomato.

3. Metalaxyl. Adding 10 mg metalaxyl to each liter of nutrient solution every 3 weeks can also effectively control tomato root diseases.

Strawberry red heart disease caused by Phytophthora can be prevented and treated with 1.6 mg metalaxyl, once every 2 weeks. Celery spot blight with 64 evil frost, manganese zinc wettable powder 800 times solution, celery soft rot agricultural streptomycin, 150 mg per liter. The concentration of pesticides in soilless cultivation is generally very low, only a few milligrams to 20-30 milligrams per liter, the dosage is too large or the local concentration is too high, it will cause drug damage. For example, when carbendazim exceeds 50 mg / L, it will kill tomato roots. Through the substrate culture supplied by drip irrigation equipment, the pesticide can be diluted to the desired concentration in the liquid storage bucket, mixed evenly and then dripped into the cultivation substrate. In the circulating hydroponic culture, fungicides should be added step by step according to the liquid storage capacity of the liquid culture tank, stirred evenly and then pumped into the cultivation bed, so as to prevent the local concentration from being too high and cause drug damage.

5. Soilless cultivation should prevent continuous cropping obstacles and infectious diseases after continuous cropping.

For example, crop rotation can reduce the harm of pathogens left by early crops. In addition, when gourd crops are cultivated in nutrient solution, such as watermelon can use bottle gourd as rootstock, grafting can also play a role in resistance to Fusarium wilt.

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