With the rapid development of greenhouse cultivation, it is not only beneficial to the production of vegetables, but also provides good conditions for the occurrence of diseases and pests. The types of pests and diseases have increased significantly, the degree of harm has increased significantly, and the sources of bacteria and insects have been provided for exposed vegetables.
First, the impact of soil on the occurrence of diseases and pests and control measures
Soil is the root environment of vegetables, and it is also a wintering place for many pathogens. In the open-air cultivation conditions, the pathogens in the soil maintain a certain balance with a large number of beneficial microorganisms. Due to the relatively simple types of vegetables cultivated in the greenhouse, the cultivation area is limited, and rotation is difficult. Due to the residual substances and roots of vegetable roots, the soil microorganisms gradually lose their balance, and the number of pathogens continues to increase, which induces diseases. The soil in greenhouses is less exposed to exposed soil, higher in temperature and humidity, the rapid proliferation of pathogens, and the lack of disease-resistant varieties in production. Soil-borne diseases are aggravated by continuous cropping years. For example, if a new greenhouse occurs, the occurrence of melon wilt disease is not timely. Effective prevention and control measures generally take only 4 to 5 hours from sporadic disease to widespread disease. The reduction in production is very serious, which in turn causes waste sheds. According to the survey, the situation of vegetable pests and diseases in greenhouses is constantly changing.
A variety of pathogenic bacteria overwintered with the diseased body in the soil and became the primary infestation source in the following year. It is an important link in the occurrence of vegetable diseases. The mortality rate of pathogenic bacteria in open field is high, and it can be infected in the growing season of vegetables. The incidence is late and the damage is light. Some diseases only occur seasonally in local areas. However, under the cultivation of greenhouses, the germs can safely pass through the winter and can also occur on an anniversary basis, which has become the enemy of the development of greenhouse vegetable production. Such as melon anthracnose, bacterial angular leaf spot, blight, cucumber, pepper, leek disease, tomato early blight, leaf mold, cowpea and bean rust, celery spot blight, a variety of vegetable sclerotia. In addition, pathogenic bacteria causing damping-off of rice seedlings and blight are both wintered and parasitized in the soil, and often occur at seedbeds in old nursery areas. Pests such as earthworms and earthworms also occur early, in large numbers and in serious harm due to warm, moist, loose and fertile soil in greenhouses and seedbeds.
Second, soil-borne diseases and underground pest control strategies
1. Disease prevention and treatment
As the greenhouses continue to be used for many years, the disease is increasing year by year and soil disinfection is necessary.
1.1 Agricultural Prevention and Control
Seedlings detoxification, high temperature stuffy shed, cornice rotation, solar soil disinfection.
1.2 Chemical Control
The use of chloropicrin, methyl bromide, and mycelia were used for soil disinfection. When transplanting, use 20% Benzoate 1000-2000 times solution, or 70% thiophanate-methyl 300-500 times solution for root immersion or planting.
2. Pest control
2.1 Poison bait trapping
In the land where the earthworms predominate, poisonous baits can be used to trap and kill. Method is: the peanut cake or wheat bran fry, per 100kg peanut cake or wheat bran add 80% trichlorfon wettable powder or 50% phoxim EC 1kg, plus 10kg water mix, dubbed bait, In the vegetable seedling stage, it was scattered on the ground in the evening ridge, and the dosage was 225-375kg/km2. It not only had a good effect on the larvae but also had a good trapping effect on the larvae of the earthworm and the earthworm. In the case where the ground tiger has a heavier land mass, 10 times of the above-mentioned one kind of pesticide can be sprayed and mixed in the fresh grass or fresh leaves of the crushed pests to make poisonous grass (poisonous vegetables) in the evening ( In order to prevent the fresh grass from drying out quickly, it is divided into small piles and applied to the fields with a dosage of 225~300kg/hm2. The dead insects are picked up in the early morning of the next day to prevent their resurrection.
2.22 spray or dusting. The fly can be sprayed with 80% dichlorvos 800-1000 times, or 2.5% deltamethrin EC on the onions, garlic vegetables and field manure heaps to kill adult insects and reduce production. The number of eggs and larvae. Use 90% trichlorfon crystals 300 to 500 times or 5% dimethoate 1000 times. Watering in the heavier plots of garlic, leeches, and flies, the application of larvae during the critical period of larval emergence. When the leek is transplanted, use 50% phoxim EC 1000 times dip.
Third, the impact of air humidity on the disease and the prevention and treatment of China's agricultural network
In the cold season and the closed insulation at night, the relative humidity of the air can reach 90~100%. The greenhouse roof and walls can be scattered on the plants after exposed. Cucumber, tomato and other vegetables have large heat capacity, and the leaves and fruits can form water film, resulting in a high humidity environment, unfavorable to the growth and development of vegetables, and the disease resistance is reduced, but it is suitable for the germination, infection and reproduction of various pathogenic fungi and bacteria. Such as cucumber downy mildew, must be 3h condensation on the leaves in order to germinate, invade the host. Once the disease occurs, it spreads and spreads rapidly, often causing an epidemic, resulting in reduced production or even no harvest. The above diseases are aggravated by various diseases and are closely related to the high humidity environment.
The main prevention and control measures: 1 Strengthen ventilation to reduce humidity and reduce the occurrence of diseases. 2 Pharmacy control, can choose chlorothalonil, green hen No.2, Green Hunter No.5 and other agents.
Fourth, the impact of temperature on the occurrence of pests and control measures
The long-term co-evolution of vegetables and pathogens has resulted in warm conditions in the greenhouse. It has generally not become a limiting factor in the epidemic of diseases. The temperature environment suitable for the growth of vegetables can usually cause morbidity. Pests and mites belong to a type of thermophilic animals, and the ambient temperature directly affects their body temperature and their life activities. The influence of temperature on pest distribution areas and the occurrence of damage is more important than humidity.
The main prevention and control measures: The choice of avermectin, chlorantranyl, chlorpyrifos and other agents (optional one).
Fifth, the host's impact on the occurrence of disease and control measures
Tomatoes infected with Phytophthora infestans only infested tomato and artichoke. The bacterial source of the tomato in the open field was from acacia, and the harm was minor. With the rapid increase of greenhouse tomato cultivation area in autumn and winter, the disease has been increasing year by year, and it has also provided a large number of bacterial sources for exposed tomatoes, which has become one of the major diseases of the year. Cucumber downy mildew is the main disease of greenhouse cucumber in winter and spring. With the development of greenhouse cultivation, several root diseases of greenhouse vegetables, such as cucumber and melon vegetables, are planted all year round, and the disease source gradually increases, which makes the disease more serious.
Control strategy: 1 selection of disease-resistant varieties. 2 Ecological control. According to the humidity and temperature conditions required by greenhouse vegetable diseases, ventilation and ventilation are carried out to make the environmental conditions unfavorable and disease development, and to facilitate the growth of vegetables. 3 fumigation (to protect the vegetables, cucumbers and other melon diseases). When starting to see the diseased leaf, use 30% chlorothalonil smoke agent (3000~3750g/hm2 each time in the greenhouse) and fumigation after closing the greenhouse in the evening. 4 chemical control. Spray with 5% chlorothalonil powder 15kg/hm2, or spray with 64% antimony wettable powder 400 times, or 70% metonate aluminum wettable powder 250 times.
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