What are the precautions for chemical weeding in wheat fields before winter?

Matters needing attention in chemical weeding in wheat field before winter

Do not use herbicides before the third leaf and after heading. Before the third leaf, the growth mechanism of wheat is tender, the detoxification ability is poor, and it is prone to phytotoxicity. After heading, wheat entered the young spike division stage. If herbicides are used, it will lead to difficulty in heading, small panicle and serious yield limitation.

Do not use herbicides when the average temperature of the day is below 5 degrees. Generally speaking, herbicides are ineffective at low temperatures and are prone to phytotoxicity. At the same time, the resistance of wheat is reduced at lower temperature, detoxification is slow, and phytotoxicity is easy to occur. When the stomata of weeds are closed at low temperature, the liquid medicine is not absorbed, so the control effect is not good and it will still cause phytotoxicity.

Don't use herbicides if the soil is too dry and there is water. If the soil is too dry, the ability of weeds to absorb liquid medicine will be reduced, resulting in poor results. If the soil water content stored in the field is too high, the ability of wheat roots to absorb nutrients will be reduced, and the resistance will also be reduced, which is prone to phytotoxicity. Generally, it is more suitable to apply pesticide in dry land and paddy-upland rotation field without sticking feet.

Yellow seedlings and weak seedlings do not use herbicides; Wheat yellow seedlings and weak seedlings have poor resistance. If chemical weeding is adopted at this time, the yellow seedlings of wheat will be aggravated and the seedlings will fall seriously. We must first promote the weak to the strong, and then we can carry out chemical weeding.

Wheat seedlings have serious pests and diseases, so don't use herbicides. If there is no seed film coating when wheat is planted, there will be more precipitation, and brown spot and sheath blight will occur seriously. At this moment, the resistance of wheat is not great, and once herbicides are used, serious phytotoxicity will occur. Be sure to see a doctor before weeding.

Don't apply pesticides before and after rain: generally, there should be no strong cooling and rainy weather for 5-7 days before and after pesticide application, which will aggravate the phytotoxicity of wheat, and at the same time, the stomata of weeds will be closed and the liquid medicine can't be absorbed, resulting in adverse consequences. If the rain causes high humidity in wheat leaves, it will store water in the field and the roots will be anaerobic, thus aggravating the phytotoxicity.

When pesticides containing methyl parathion (chlorpyrifos, omethoate) and hydroxybenzoic acid (isoprocarb and indoxacarb) are used, herbicides can only be sprayed after 7- 10 days. Because sometimes the occurrence of wheat planthopper, aphid, LEPIDOPTERA insect and meadow moth is serious, if methyl parathion or hydroxybenzoic acid pesticides are used, it will take 7- 10 days.

Mix effectively and do not spray repeatedly.

Because of the high resistance and variety of weeds, it is necessary to mix the selected pesticides effectively. Usually, pesticides such as carfentrazone and dimethyl carbon tetrachloride are used separately from weeds to prevent phytotoxicity caused by mixed pesticides. At the same time, the pesticides currently used are basically drugs spread by internal inhalation, so don't re-spray, otherwise it will cause phytotoxicity.

Chemical weeding in wheat field should be done as follows: early weeding, small weeding, temperature-loving, and appropriate mixed chemical control. Generally, in pastoral areas where weeds are mainly convolvulus, metsulfuron, mesotrione, cyhalofop-butyl and other chemicals can be mixed with isoproturon.

Broadleaf plants, weeds (such as pig gizzard and chickweed) can be mixed with chemicals (such as clopidogrel and fomesafen). If there is a garden where Veronica and Descurainia sophia are planted, it is recommended to choose a mixed chemical containing dimethyl tetrachloroisooctyl ester.