What are the control methods and available herbicides for wild weeds in wheat fields?
Weeds are important pests that harm wheat yields, so they must be removed in time, and experience shows that removing field weeds before winter can increase yields. So how should wild weeds in wheat be controlled? Which herbicides can be used?
1. How to control wild weeds in wheat?
1. Pre-winter control
Mainly to control grass weeds, roughly before early November, when wheat has grown 4-5 leaves and weeds generally have grown to 2 leaves and 1 heart; at this time the control effect is best.
2. Spring control
Mainly to control broadleaf weeds, from late February to early March; the control period should be early rather than late, because too late makes weed control difficult and may cause herbicide damage to wheat.
In addition, pre-winter weed control in wheat is currently entering a critical period. Here, a special reminder to the vast number of wheat growers is to choose the right herbicide and master the spraying technique well, and according to temperature, soil moisture, seedling age and weed age, seize every opportunity to do the current chemical control work well.
1. Do not apply herbicides before wheat has 4 leaves or after jointing
Most wheat field herbicides are applied after 4 leaves and stopped at the wheat jointing stage. Before the 4-leaf stage, wheat is relatively tender, with low detoxification ability and immunity, and is prone to herbicide damage; after the jointing stage, wheat enters the booting stage, also the most fragile and critical period of its life, and applying herbicides at this time very easily causes herbicide damage, sometimes causing wheat heads to fail to emerge or become deformed, seriously affecting the final yield. Apart from herbicides such as clopyralid and fluroxypyr, which can be used at half rate after jointing, it is best not to try other herbicides.
2. Do not use herbicides when the daily average temperature is below 8 degrees
Except for a few herbicides (florasulam, which is relatively tolerant of low temperatures), general herbicides have unsatisfactory effects in low-temperature weather and easily cause herbicide damage. Therefore, it is best to apply them when the daily minimum temperature is above 8 degrees; the higher the temperature, the better the weed control effect, because weeds grow vigorously by absorbing light, their stomata open, and they easily absorb water and herbicide solution, while low temperature has the opposite effect.
3. Do not use herbicides in dry weather
In addition to checking the temperature when spraying herbicides, you must also grasp the soil moisture. Under severe drought conditions, seize the opportunity when the wheat field is watered and apply the herbicide in time to ensure the herbicide effect is exerted. The effect of most herbicides requires a certain amount of soil moisture, and soil moisture of 40%-60% is most conducive to the herbicide effect.
4. Do not use herbicides when wheat seedlings are weak and roots are exposed
Generally, winter wheat fields undergo straw return, and the soil is relatively loose. If abnormal weather occurs in a given year (such as a warm winter and drought), the wheat roots may be unable to penetrate deeply because the soil is too loose, or part of the root system may be exposed. Such wheat is easily damaged by freezing and water shortage, relatively sensitive and fragile, and applying herbicides at this time easily harms the wheat.
5. Do not use herbicides when wheat has disease
In recent years, seed-borne or soil-borne diseases such as wheat sheath blight, root rot and take-all have occurred frequently. Diseased wheat has extremely low resistance, and once herbicide damage occurs, it is not easy to recover. Therefore, for plots with severe wheat disease, it is generally not recommended to use herbicides; first treat the disease and strengthen the seedlings.
6. Do not use herbicides before and after heavy rain or before the arrival of cold air
Using herbicides before and after heavy rain or before the arrival of cold air affects the weed control effect on the one hand, and on the other hand very easily causes herbicide damage. Under severe weather such as frost, rain and snow, hail and cold waves, the use of herbicides is prohibited. These all belong to severe weather. In particular, herbicides must not be used in the 7 days before a late spring cold spell. When applying herbicides in winter, pay more attention to the weather forecast.
7. Do not apply herbicides within 7 days before or after using organophosphorus and carbamate pesticides
We all know that after applying organophosphorus or carbamate pesticides in corn fields, an interval of 7 days is needed before herbicides can be used, and after applying such insecticides in wheat fields, at least a 7-day interval is also needed before herbicides can be used. Otherwise, it easily causes wheat yellowing and leaf burn, because organophosphorus pesticides reduce wheat's ability to degrade herbicides, and using herbicides immediately afterward easily leads to herbicide damage.
8. Do not spray twice or miss spots
When using herbicides, be sure to spray evenly. If some places are missed or under-sprayed, the weeds receive uneven herbicide and the control effect is poor; secondly, remember not to spray twice, as this will cause wheat yellowing and easily cause herbicide damage.
2. Which herbicides can be used to control wild weeds in wheat?
1. Weeds in wheat fields are divided into dicotyledonous weeds and monocotyledonous weeds. Dicotyledonous weeds are also called broadleaf weeds. As everyone knows, soybean and peanut are dicotyledonous plants. Dicotyledonous weeds are similar to soybean and peanut and also have two cotyledons when they emerge. Like corn, monocotyledonous weeds have only one cotyledon. These two types of weeds differ greatly in their sensitivity to herbicides. From green-up to before jointing, common dicotyledonous weeds in wheat fields include flixweed (Descurainia sophia), cleavers (Galium aparine), chickweed (Stellaria media), shepherd's purse (Capsella bursa-pastoris), Silene conoidea, Lithospermum arvense, Centipeda minima, sun spurge (Euphorbia helioscopia) and so on.
2. 2,4-D butyl ester emulsifiable concentrate: To control dicotyledonous weeds, you can choose 72% 2,4-D butyl ester emulsifiable concentrate, or 20% MCPA emulsifiable concentrate, or 75% tribenuron-methyl dry suspension concentrate, or 20% fluroxypyr emulsifiable concentrate, etc.
For wheat fields dominated by flixweed, you can choose 72% 2,4-D butyl ester emulsifiable concentrate at 30-50 ml per mu; or 20% MCPA at 250-300 ml per mu, diluted with 30 kg of water, and sprayed evenly.
3. Tribenuron-methyl: Another herbicide used in spring to control broadleaf weeds in wheat fields is tribenuron-methyl, also called broadleaf clean. Tribenuron-methyl is a highly effective herbicide for controlling broadleaf weeds in wheat fields, and its suitable application period is longer than that of 2,4-D butyl ester. From when wheat seedlings grow two leaves in autumn to before wheat jointing, it is safe for wheat. The commonly used form is 75% dry suspension concentrate, applied at 0.9 to 1.4 grams per mu, diluted with 30 kg of water, and sprayed evenly. Application before winter from the 3-leaf stage to the 4-leaf stage also has a very good effect.
4. Other herbicides: For wheat fields dominated by cleavers and Lithospermum arvense, using a mixture of fluroxypyr and MCPA has a good weed control effect. The specific dosage is: 20-25 ml of 20% fluroxypyr per mu, plus 125 ml of 20% MCPA, diluted with 30 kg of water, and sprayed evenly.
To control cleavers, you can also use a mixture of dicamba and 2,4-D butyl ester: 13.3 ml of 48% dicamba aqueous solution per mu plus 25 ml of 72% 2,4-D butyl ester emulsifiable concentrate, diluted with 30 kg of water, and sprayed evenly.
To control monocotyledonous weeds such as wild oat and shortawn foxtail, the following herbicides can be chosen: 36% diclofop-methyl emulsifiable concentrate, 6.9% fenoxaprop-P-ethyl suspension concentrate, and 25% chlorotoluron wettable powder, etc.