When is the best time to remove weeds from wheat in spring? Which herbicide should be chosen? How can it be applied for the best effect?

After growing for a certain period, wheat will produce many weeds, and these weeds not only absorb nutrients from the soil but also cause poor growth of the wheat. For this reason, wheat must be weeded regularly, and there are many particular points about weeding wheat. Many farmer friends often cannot judge them accurately, which easily leads to poor weed control or herbicide damage, affecting the normal growth of wheat. So when is the best time to remove weeds from wheat in spring? Which herbicide should be chosen? How can it be applied for the best effect?

In fact, wheat weeding is roughly divided into two stages around the Spring Festival, namely the wheat seedling stage and the green-up stage. During this period, the weed control effect is relatively good, but how can herbicide damage be avoided? This is related to the ingredients of many herbicides, as well as to winter temperatures, and there are also some other factors that need to be understood and controlled.

For example, during the wheat seedling stage, when the winter daytime temperature is below 6°C, do not apply herbicides such as mesosulfuron-methyl, fenoxaprop-P-ethyl, clodinafop-propargyl, and bensulfuron-methyl. After the strong temperature drop passes, the weather will tend to become stable, and at that time herbicides can be used according to local conditions.

In addition, the weed control effect is also affected by soil moisture. When the weather is especially dry, that is, when soil moisture is poor, the effect of the herbicide will be greatly reduced. When soil moisture is 40%-60%, the herbicide effect is easily exerted and the result will be better. At the same time, the spraying time must also be well controlled. Generally, choose to spray herbicides after 10 a.m. and before 4 p.m. The dosage must be prepared according to the requirements on the label; neither exceeding the amount nor using too little is advisable.

If weeding was not done in time before the Spring Festival or the weed control was not ideal, then weed control should be carried out in time after the Spring Festival. At this time, wheat enters the green-up stage, and weed growth also enters a vigorous period, so the weed control effect is good.

However, after wheat jointing, herbicides should not be used, otherwise it is very easy to cause herbicide damage of varying degrees.

For example, the MCPA and bentazone mixture can control many kinds of broadleaf weeds. Use 125 mL of 20% MCPA aqueous solution plus 100 mL of 40% bentazone aqueous solution per mu, mix with 30 kg of water and spray. The spraying time is best after wheat tillering and before jointing, and this mixture is only suitable for application where the following crop is rice.

Seedlings of grass-family crops such as wheat and rice are very sensitive to MCPA. After the 3-4 leaf stage, resistance gradually increases, and it is strongest at the end of tillering. By the young ear differentiation stage, sensitivity rises again. Therefore, application is generally required from the 4-leaf stage to before jointing.

40% dicamba and 2,4—D butyl ester cannot be used after wheat jointing, otherwise it is very easy to cause herbicide damage to wheat. If used too late, it will cause wheat to fail to set grain. Applying herbicide from jointing to booting stage of wheat occurs when wheat is in the period of simultaneous vegetative growth and reproductive growth, when drug resistance is poor and sensitivity is high. It is very easy to cause herbicide damage, inhibit wheat growth, cause tiller death, deformed wheat ears, and slow growth. Therefore, herbicide should be applied before jointing. For example, during the jointing and booting stage, wheat is relatively sensitive to many herbicides such as quizalofop-P-ethyl, MCPA, and dicamba. After application, it is very easy to cause wheat leaves to curl, wheat seedlings to turn yellow, growth to be inhibited, ear differentiation to be damaged, and normal heading to fail or wheat ears to become deformed.

Applying herbicides containing tribenuron-methyl in wheat fields in spring can easily harm following crops such as cotton seedlings and soybean, so it should be applied before winter, and the interval from the sowing period of the following crop should be no less than 60 days to ensure the safety of the following crop.

To control grass-family weeds such as shortawn foxtail in wheat fields in spring, herbicides such as quizalofop-P-ethyl should preferably be selected. Isoproturon has a good control effect on weeds with small leaf age. During the wheat jointing stage, weeds are older, and the weed control effect of isoproturon is poor.

Relatively speaking, herbicides such as carfentrazone-ethyl and fluroxypyr, which are suitable for controlling broadleaf weeds in wheat fields, are safer for wheat seedlings. Applied after wheat jointing, they generally will not have too great an impact on wheat growth and development. Moreover, these herbicides have a short residual period in the field, and after spring application in wheat fields they will not produce adverse effects on following crops. Herbicides such as tribenuron-methyl have a longer residual effect period, and generally should not be applied after wheat jointing in spring, so as to avoid herbicide damage to following crops.

Considering that applying herbicides may have adverse effects on wheat that has already jointed, a spot-treatment method can be used when applying in the field, mainly spraying where weeds are especially numerous. At the same time, note that even where weeds are numerous, do not blindly repeat spraying, to prevent excessive application in local areas from having adverse effects on wheat.