Safety agent introduction

Herbicides, as the most widely used pesticide, liberate people from tedious manual weeding. As an important way to replace manual weeding with chemical pesticides, it is like a double-edged sword, and the drug damage problem it brings is also a huge problem for agricultural practitioners.

The harm of herbicides to crops has been an important problem that affects agricultural yield stability and increase.

First, the cause of herbicide harm

Herbicide damage may include a combination of factors, and insecticidal fungicide damage is different, herbicide damage will bring huge losses, light will reduce production, heavy particles no harvest.

Herbicide damage can be roughly divided into the following five categories:

1. Technical drug damage

It is undeniable that at present, the vast majority of agricultural practitioners in China are still not enough plant protection technology, and most farmers are still relying on empiricism, which makes the drug damage caused by improper use frequent.

This kind of technical drug damage is mainly caused by the improper use or selection of application dose, application period, mixed use of herbicides, application equipment, etc. About the amount of medicine, most farmers in the field of medicine, because there is no special measuring tools, often intentionally or privately increase the amount of medicine, think that "the higher the concentration, the better the effect", and in the treatment of herbicides also take for granted attitude, mistakenly think that the greater the amount of medicine, the better the effect of weeding. Excessive use is easy to cause drug damage to crops, especially in the application of ultra-high effectiveness herbicides and low temperature, rainy climate conditions, drug damage phenomenon will be more common and serious, and in the crop seedling stage will be more prominent.

In addition, it is still common for Chinese farmers to spray various pesticides with the same set of sprayers, and the use of tangential centrifugal vortex core nozzle, which leads farmers to adopt the backward spraying method of swinging spray rod, which is difficult to ensure uniform spraying, which is precisely the use of herbicides. Especially when highly active herbicides must be avoided.

The main cause of herbicide injury is the lack of application technology.

2. Residual drug damage

In the 1980s, the major pesticide companies in the world competed to develop sulfonylurea and imidazolinone herbicides, which have the advantages of high activity, good weed control effect, wide weed killing spectrum and low drug cost. However, its disadvantages are also very obvious, the residual time in the soil is long, generally up to 2 to 3 years, as long as 4 years, and the use of continuous cropping and rotation farmland is easy to cause drug damage to subsequent crops, production reduction or even extinction. Long residual herbicides may cause damage to the next crop during crop rotation and land transfer.

For example, in the mid-1990s in Jiangsu, Anhui and other places, due to the use of amphenesulon, a large area of drug damage was found in the later rice, and after 2000, amphenesulon drug damage incidents occurred more frequently, which has seriously affected agricultural production. As highly effective sulfonylurea herbicides, chlorsulfuron and methylsulfuron have good herbicide effect, but they have serious drug damage to the next crop of cotton, corn, soybean, peanut and other dry crops, and also have a certain inhibitory effect on rice. Even if the soil is ploughed, the adverse effects of residual chemicals on the later crops cannot be eliminated.

3. Drifting drug injury

Some herbicides have large drift, which is easy to drift to neighboring crops when applied on specified crops, resulting in drift damage. The common contaminant is 2, 4-D butyl ester and its mixtures. An important reason for the ban of wheat straw in the United States before is the easy drifting characteristics of wheat straw. Hormonal herbicides are easy to cause drift toxicity.

The fog point of 2, 4-D related products can drift to a distance of 1000m when used, and it is applied on the corn field, and the neighboring soybeans, sunflower, zucchini and other crops are prone to drug damage. In 2007, wine mountain grapes in Jilin City, Jilin Province suffered serious herbicide damage in history, which was confirmed to be caused by 2, 4-D butyl ester sprayed on corn fields and escaped to nearby grape growing areas. According to statistics, the land affected by drift drug damage, the land with light damage can reduce production by 30% to 50%, and the serious land even has no harvest. For some pesticide herbicides (such as glyphosate), the droplet itself is not strong, and conventional spray generally will not drift to neighboring crops, but it is very easy to drift to neighboring crops in windy weather conditions.

4. Conditional drug injury

Weather conditions such as temperature, humidity, light, wind and rain play a vital role in the efficacy of herbicides, but may also cause drug harm. Studies have reported that when the soil temperature is below 15 ° C, the use of trifluorocarboxyfen on soybeans, or the use of acetylide on wheat when the soil temperature is below 5 ° C, it will cause drug damage because the drug is not easy to degrade in the plant.

Acetochlor, as a widely used herbicide for soil treatment, is safe for crops under normal conditions, but it is very easy to suffer from drug damage in the case of heavy rain after application.

5. Quality drug harm

In the case of chaos in the pesticide market, some illegal manufacturers and dealers will introduce some fake and inferior herbicides to the market, because these herbicides are three no products, poor quality. The use of this kind of herbicides, light can not achieve good weeding effect, heavy may produce drug damage.

Second, different types of herbicides caused by the symptoms of drug harm

1. Aromatic oxyphenoxypropionic acid herbicides

This kind of herbicide is relatively easy to form drug damage to crops, first affecting young growth tissues, yellow heart leaves, then old leaves yellow, purple, and then die, the growth of the whole plant is inhibited, and the plant is short.

2. Dinitroaniline herbicides

The typical symptoms of this herbicide are inhibited root growth, short and thick roots, thickening of the root tip, enlargement of the stem base or tycotyl, and failure to emerge when severely damaged.

3. Triazine herbicides

The symptoms of this kind of herbicide on crops are intervein loss of green, yellow leaf edge, and then leaf completely loss of green, dead. Old leaves suffer more than new ones.

4. Replace urea herbicides

These herbicides are similar to triazepines in their toxicity.

5. Diphenyl ether herbicides

The symptoms of this herbicide are leaf necrosis. Severe damage, the whole leaf dry, fall off.

6. Thiocarbamate herbicides

This herbicide causes the leaves of gramineous crops to fail to pull out of the coleoblast properly, and the leaves of broad-leaved crops are deformed into cups.

7. Amide herbicides

The typical symptoms of such herbicides are stunting and deformity of seedlings. The damage symptoms of monocotyledonous crops are tightly curled heart leaf, which cannot unfold normally. Dicotyledonous seedling leaves are cupped, the midvein is shortened, and the tip of the leaf is concave.

8. Bipyridine herbicides

The symptoms of this herbicide are burning spots, dying and shedding of the leaves.

9. Sulfonylurea and imidazolinone herbicides

The symptoms of this kind of herbicide appear slowly, and only gradually appear in the meristem area greening and necrosis 1 ~ 2 weeks after application, and then leaf greening and necrosis occur.

10. Hormonal herbicides

The typical symptoms of crop injury caused by hormone herbicides are deformities, such as leaf shriveling, scallion leaf shape, stem and petiole curvature, difficult heading deformity.

The harm caused by herbicides is not without solution, and the emergence of herbicide safety agents can reduce the possibility of some herbicides causing drug harm.

Third, what is herbicide safety agent?

Herbicide safety agent (safener), also known as antidote or protectant, refers to the chemical compounds used to protect crops from herbicides, thereby increasing the safety of crops and improving the effectiveness of weed control.

Herbicide safety agents do not solve everything, it is only used to improve herbicide selectivity, and enhance the stress resistance of the relevant crops. It has a certain preventive effect on technical drug damage and drift drug damage.

Fourth, the mechanism of herbicide safety agent

The mechanism of herbicide safety agents is different, but in summary, they can regulate the metabolism of herbicides in crops, and most of the safety agents enhance the metabolic detoxification of herbicides like "biological regulators". An effective safety agent must be able to be absorbed by the roots or buds of the protected crop and react with the crop protection system to increase the tolerance of the protected crop to a specific herbicide. It has been proved that safety agents are effective in protecting crops by absorbing and enriching, protecting gene transcription and enhancing enzyme activity.

However, the mechanism of intermembrane sensors and signal transduction systems in the protection process of herbicide safety agents remains unclear.

Five, the development of herbicide safety agents

In 1947, Hoffmann found that when 2, 4-D was applied to tomatoes that had previously been treated with 2, 4, 6-DDT, the tomatoes were not harmful. When applied to wheat that had previously been treated with 2, 4-D, the wheat was not toxic. Hoffmann believes that this is not an accidental phenomenon, and after long-term research on this relationship, he first proposed the concept of safety agent in 1962. After several years of research, Hoffmann developed 1, 8-naphthalic anhydride (NA), the first safety agent that did not cause harm when applying thiochlorate herbicides to NA-treated corn. NA was commercialized by Gulfoil in 1972. Hundreds of safety-agent compounds have since been developed, and more than 30 have been commercialized.