It is safest to apply herbicides 40 days after sowing the winter wheat after pouring the headwater (the first water). At this time, the wheat is in the 4-leaf or 4-leaf 1-heart stage and is more tolerant to herbicides. Weeding should be done after 4 leaves. agent is the safest.

In addition, at the 4-leaf stage of wheat, most of the weeds have emerged, and the grass age is relatively small. Wheat has no tillers and few leaves, so it is easier to kill weeds. Herbicides are most effective at this time. So what are the precautions for spraying wheat herbicides?
1. Strictly control the temperature.
Herbicides are generally marked as ready for use at 2°C or 5°C. So, do the 2°C and 5°C mentioned here refer to the temperature during use or the lowest temperature?
The answer is the latter. The temperature mentioned here refers to the minimum temperature, which means that the minimum temperature can be used above 2℃, and the temperature should not be lower than this two days before and after applying herbicide.
2. It is forbidden to use medicine on windy days.
Applying pesticides on windy days can easily cause herbicides to drift away, which may not be effective. It may also spread to greenhouse crops or other crops, causing herbicide damage. Therefore, be sure to avoid using pesticides on windy days.
3. It is forbidden to use medicine in bad weather.
It is forbidden to use herbicides in severe weather such as frost, rain, snow, hail, cold snaps, etc. We should also pay attention to try not to have such severe weather before and after applying herbicides. Farmers must pay attention to the weather forecast.

4. Do not use herbicides when the wheat seedlings are weak and the roots are exposed.
Generally, straw is returned to the field in winter wheat fields, and the plots are relatively loose. If you encounter years with abnormal weather, such as years with warm winters and droughts, you must be aware that the wheat roots may not be able to penetrate deeply because the soil is too loose, or part of the roots may be exposed. Young wheat can easily cause frostbite and lack of water. Such wheat seedlings are the most sensitive and fragile. If herbicides are applied at this time, it will easily cause certain damage to the wheat.
5. Do not use herbicides when wheat is sick.
In recent years, seed-borne or soil-borne diseases such as wheat sheath blight, root rot, and total rot have occurred frequently. Before using herbicides, farmers should first check whether their wheat seedlings are sick. If the wheat is sick, it is best not to use herbicides. agent. It is recommended that farmers pay attention to using special pesticides to dress wheat before sowing to prevent the occurrence of diseases.
6. When using herbicides, be sure to dilute them twice.
Some farmer friends want to save trouble and directly pour the herbicide into the sprayer, and just find a branch to stir it. This method of mixing medicine is very unscientific. Because most herbicide products come with auxiliaries, the auxiliaries play a role in penetration enhancement and are usually relatively viscous. If poured directly into the sprayer, they may sink to the bottom of the barrel. If sufficient stirring is not carried out, auxiliaries may cause auxiliary effects. The herbicide packaged in the agent cannot be dissolved, which may lead to two consequences:

One is that after all the herbicides have been sprayed, part of the herbicide is still undissolved at the bottom of the barrel, resulting in waste;
Another consequence is that the wheat field herbicide applied is very light at the beginning, but the herbicide applied at the end is very heavy. Therefore, when using herbicides, be sure to pay attention to secondary dilution.
The correct preparation method is the secondary dilution method: first add a small amount of water to prepare the mother solution, then pour it into a sprayer containing a certain amount of water, then add the required amount of water, stir while adding, and mix thoroughly to dilute to the required concentration. Do not pour the agent first and then add water. This will cause the agent to easily deposit on the water suction pipe of the sprayer. The concentration of the solution sprayed first will be high and it is easy to cause phytotoxicity. The concentration of the solution sprayed later will be low and the weeding effect will be poor. Do not pour the agent into a sprayer filled with a large amount of water at once. In this case, the wettable powder often floats on the water surface or forms small pieces and is unevenly distributed. Not only does the effect not be guaranteed, but the nozzle holes are easily blocked during spraying. In addition, the medicinal solution should be prepared with clean water.
7. Herbicides must be used strictly in accordance with regulations to avoid excessive use.
When some farmers apply herbicides, they spray several times in areas with thick grass, or they spray the remaining herbicides all over the last plot for fear of wasting it. This approach can easily lead to herbicide damage. This is because herbicides are safe for wheat at normal concentrations, but if used excessively, the wheat itself cannot decompose and will cause damage to the wheat.

8. Correctly view the phenomenon of yellowing and squatting of seedlings caused by herbicides.
After the use of some herbicides, the wheat leaf tips will turn yellow for a short period of time. This is a normal phenomenon of squatting seedlings. Generally, it can recover on its own when the wheat turns green. This phenomenon will not cause a reduction in production, but can promote an increase in wheat production. It can prevent wheat from affecting its reproductive growth due to excessive vegetative growth, so farmers do not have to worry when encountering this phenomenon.
9. Strictly control the temperature.
Finally, I would like to remind everyone that when weeding wheat weeds, we should pay attention to the weather temperature and humidity. When using pesticides, the average temperature should be higher than 6 degrees. If the soil is relatively dry, we should pay attention to increasing water consumption. If there is stagnant water, it will affect the wheat herbicides. The efficacy of the medicine is exerted.