What is a Weeder Class?

Herbicide ^[1] (herbicide) refers to the agent that can cause weeds to die completely or selectively, also known as herbicides, a class of substances used to destroy or inhibit plant growth.

Herbicides are also called herbicides. Chemicals that can kill weeds or harmful plants without affecting the normal growth of crops. It can be used to control weeds in farmland or kill weeds or shrubs in non-agricultural land. According to their characteristics, they can be divided into selective herbicides and biocidal herbicides. Selective herbicide refers to the use of certain doses and concentrations, which can selectively kill certain types of plants without harming other types of plants ^[1]

The beginning of chemical weeding in farmland can be traced back to the end of the 19th century. During the control of European grape downy mildew, it was occasionally found

Herbicides can be classified according to their mode of action, application site, source of compounds, etc. According to the action characteristics of herbicides, they are usually divided into two categories: preemergent herbicides and postemergent herbicides. ^[2]

• Acetochlor

Compared with pesticides and fungicides, herbicides have higher technical requirements. Improper use of pesticides and fungicides may only affect the effectiveness of prevention and control. The improper use of herbicides is related to the safety of crop growth. To ensure the safe and efficient use of herbicides, the key technologies are introduced below for reference.

Strictly grasp the sensitivity of crops to herbicides. Different crops have different levels of sensitivity to herbicides. If you do not choose a pesticide based on the sensitivity of the crop to the herbicide, even if you use a herbicide that is safe for the crop, it is sometimes easy to produce pesticide damage. Generally, herbicides for controlling broad-leaved weeds are sensitive to dicotyledon crops, and herbicides for controlling weeds of grasses are sensitive to grasses. For example, 2,4-drip and dimethyl tetrachloride have good effects on broad-leaf weeds, but they are sensitive to broad-leaf crops such as cotton, rape, melons, beans, peanuts, potatoes, tobacco, etc., and are prone to phytotoxicity . Acetochlor is suitable for broad-leaved crops such as corn, peanuts, cotton, and soybeans, but it is easy to cause harm to wheat.

• Herbicides cause serious harm to the human body and other organisms

Acute poisoning

According to the World Health Organization and the United Nations Environment Programme, more than 1 million people are poisoned by herbicides worldwide each year, and 100,000 of them die. The situation is even worse in developing countries. There are nearly one million accidents of herbicide poisoning in China each year, and more than 20,000 people die. Reported by CCTV on September 24, 1995, Guangxi

First, herbicide damage is closely related to environmental conditions. usually,

The mixed use of herbicides and mutual chemical reactions will affect the effect of herbicides. Understand how they interact to achieve the best mix of results. China Pesticide First Network hereby summarizes the following information for your reference: Type of interaction

When different herbicide varieties are mixed and used, herbicides will interact with each other, and the types of interactions can be divided into: addition, synergy and antagonism.

1. Addition

Additive effect means that the actual herbicidal effect of the two herbicides combined is equal to the sum of the herbicidal effects of the two herbicides calculated according to the relevant model.

2. Synergy

Synergistic effect means that the actual herbicidal effect of the two herbicides combined is greater than the sum of the herbicidal effects of the two herbicides calculated according to the relevant model.

3 Antagonism

Antagonistic effect means that the actual herbicidal effect of the two herbicides mixed is less than the sum of the herbicidal effects of the two herbicides alone calculated according to the relevant model.

Mutual judgment method

According to the definitions of different interaction types above, judging the type of interaction between herbicides is affected by the calculation method (the relevant model) of the theoretical value of the combined action between herbicides. Different models calculate different theoretical values, which may lead to different types of interactions. Two commonly used models are the additive dose model and the multiplicative survival model.

1. Dose-plus model

The dose-addition model assumes that one herbicide is replaced by another herbicide at an equivalent dose, and its toxicity is unchanged. Figure 5-6-1 is the equivalent line diagram, which more intuitively represents the dose addition model. Effective medium amount (ED50) of herbicide A and herbicide B The straight line connecting the two points is the equivalent line of the effective medium amount of the two herbicides combined. If the observed value of the two herbicides mixed is on this equivalent line, the mutual effect between the two kinds of herbicides is additive; if the observed value of the two herbicides mixed is below the equivalent line, then Interaction between these two herbicides

For the plots of eggplant, pepper, cabbage, radish, cabbage, cabbage, if used before, the midazolam must be planted at an interval of 40 months; chlorosulfuron must be planted at an interval of 36 months; nicotine Long, the effective amount of active ingredient per hectare exceeds 60 grams, that is, 4% nicosulfuron exceeds 100 ml per acre, and it must be planted at intervals of 18 months; with saflufenacil, 48-60 grams of active ingredient per hectare is used, that is, 80% saflufenacil, 3.2-4 grams per mu, must be planted at intervals of 26 months; used

With the modernization of agriculture, farmers also use a large number of high-tech products in agricultural production, such as a series of chemical products such as biological pesticides and pesticide mixtures. However, the most popular pesticide products are herbicides, so the sales of herbicides has been First in pesticides. However, there are many kinds of herbicides on the market, and at the same time, the application technology is also high. If there is a little care in the application, problems such as pesticide damage and poor herbicidal effects will occur. So, how to master the selection of herbicide varieties and their application technology is the key to improving the herbicide effect of herbicides. The author of China Pesticide First Net has analyzed and summarized how to improve the herbicide effect of herbicides.

How to increase the effectiveness of herbicides:

1. Select a suitable herbicide because each herbicide has a certain herbicidal spectrum, which is biocidal and selective. Therefore, it is necessary to select effective herbicides according to the types of crops and the main varieties of weeds. At the same time, the herbicide should be selected according to the farming system. In addition, pay attention to mixing and alternating herbicides. As the same herbicide is used continuously for many years, it is easy to cause sensitive weeds to gradually decrease and resistance to weeds to increase. Therefore, herbicides must be used in combination and alternately between years to achieve the purpose of long-term control of weeds.

2. Select the best period of application. According to the nature of the herbicide, weed occurrence period, weed and crop growth period, select the appropriate period of application. There are many kinds of herbicides, such as stem and leaf treatment agents, soil treatment agents, contact herbicides, biocidal herbicides, etc. Some are suitable for pre-emergent weeding, and some are suitable for stem and leaf weeding. Soil treatment is to spray herbicides directly on the soil surface to kill newly germinated weeds. For example, duor, acetochlor, etc. should be used before the weeds are unearthed after the crops are sown, and after the emergence of the weeds, the medicines are not only ineffective, and some may harm the crops. Therefore, it is important to choose the optimal period of herbicide application.

3. The effect of herbicide is proportional to the temperature. When the temperature is high, the function of weeds to absorb and transport herbicides is strong, and the herbicide activity is also high, and it is easy to give full play to the herbicidal effect at the site of the weeds. The test results show that the higher the temperature of the air and the soil, the more significant the herbicidal effect when the herbicide is applied, especially the herbicidal efficacy of the herbicide in stem and leaf treatment can be greatly improved, and the use of the herbicide in low temperature weather conditions Not only the effect will be significantly reduced, but the detoxification effect of the crops will be slow due to the low temperature, which will easily induce drug damage. The temperature of the herbicide application is preferably 20 to 35 ° C. The effect of air humidity on the use of herbicides is also The effect is obvious. Applying stem and leaf herbicides under relatively high air humidity can prolong the residence time of the herbicides on the weed leaves, help the weed leaves to open their stomata, and absorb a large amount of herbicides to improve The purpose of the herbicidal effect is that after the soil treatment herbicide is absorbed, it will be conducted upward with a large amount of water, which is beneficial to inhibit photosynthesis and can significantly improve the herbicidal effect. Therefore, when using herbicides, the greater the humidity of the air, the more obvious the herbicidal effect; otherwise, the herbicidal effect will be reduced.