How to control pests and diseases of tomatoes planted in the open air?

According to personal experience and knowledge, briefly describe the general process: because of China's vast territory, the cultivation time may be different. Take our place as an example, other places can refer to the local planting time and management technology.

In our Beijing-Tianjin-Hebei region, the approximate time for cultivating tomatoes in the open field in spring is from late April to early May. When planting, it is best to dip the roots or holes with thiamethoxam, thiamethoxam and other chemicals 1000 times, so that the effective period of prevention and control of sucking insect pests such as aphids, whiteflies and thrips can last for more than 30 days. In the later stage, imidacloprid, pymetrozine, dinotefuran, deltamethrin and other insecticides can be used for foliar spraying.

Generally, the high temperature above 30 degrees Celsius will appear in mid-May, and at this time, aphids and other pests have appeared in large numbers. At the same time, we should pay attention to preventing plant virus diseases. Spraying amino oligosaccharides and glucomannan on leaves can improve the antiviral ability of plants. In case of viral diseases, it is necessary to spray antiviral agents, such as halofop, Kedubao, Virus A, ningnanmycin, etc. Timely use of brassinolide to prevent the occurrence of viral diseases.

Diseases such as gray mold and Sclerotinia sclerotiorum may occur in the early stage of low temperature, so fungicides such as fludioxonil and azoxystrobin should be added to the flower dipping agent. Once the central diseased plant is found, the diseased fruits and leaves should be removed in time and taken out of the field for centralized incineration. At the same time, metronidazole, boscalid, nongliling and other fungicides should be sprayed.

In case of continuous rainy weather, diseases such as late blight may easily occur. Therefore, we should pay attention to listening to the weather forecast, and it is best to spray pyraclostrobin and other protective fungicides once before 12-24 hours of continuous rain. After the disease occurs, protective fungicides should be mixed with therapeutic fungicides, such as dimethomorph, oxazolidinone, cymoxanil, propamocarb, etc., to control the economic losses caused by the disease in a small range.

Due to the slow growth of tomato seedlings and the need for proper water control before fruit setting, sometimes it will inevitably lead to soil drought, affect the demand for water and fertilizer for tomatoes, and lead to calcium deficiency leading to navel rot and small head at the first ear. In this case, if you can't water, you can spray some fertilizer on the leaves to deal with the emergency. For example, calcium can be supplemented by spraying 200 times calcium chloride or 100 times calcium superphosphate solution, boron by 1000 times borax solution, nitrogen by 200-300 times urea solution, phosphorus by 200-300 times potassium dihydrogen phosphate solution, and nitrogen by 160 times potassium nitrate solution.

After entering the middle and late growth stage, the field should pay attention to seeing dry and wet. In order to avoid excessive drought, watering or rain, a large number of fruits are cracked.

In order to prevent sunburn, tomato ears are usually placed under the leaves in the frame and cannot be exposed. In order to control fruit-eating pests such as cotton bollworm, it is generally necessary to spray effective pesticides in time according to the insect situation, such as emamectin benzoate, lufenuron, indoxacarb, fipronil, fipronil, etc. , and pay attention to reasonable mixing and rotation. Pay attention to spraying fruit.

When it is warm and humid, we should pay attention to the prevention and control of tea yellow mites. Generally visible from late May to mid-June. Because its symptoms are similar to viral diseases, it is sometimes abused. Generally, abamectin and pyridaben can be sprayed, mainly on the tender tips and the back of leaves, taking into account the front of leaves.

If there are dead trees in the field, if it is not caused by pests, you can irrigate the roots with kocide (copper hydroxide) or quicklime water. Basically, both true and bacterial diseases are effective. Moreover, foliar spraying kocide can also prevent a variety of tomato fungal and bacterial diseases, but it needs to be used alone. Fungal diseases can be basically controlled in pyraclostrobin, but when serious diseases occur, corresponding fungicides with therapeutic effects should be matched according to the types of diseases, and they can only be used at ordinary times.