Weeds in Peanut Fields and the Timing and Formulations of Efficient Post-Emergence Herbicides

Everyone uses post-emergence herbicides on peanuts every year, and every year some people use them poorly, still causing herbicide damage, or finding that after spraying there is no effect. So when should post-emergence herbicides be applied to peanuts? Which one is good?

Types of weeds in peanut fields

There are mainly three major categories of weeds in peanut fields: grass weeds, broadleaf weeds and sedge weeds. In the Huang-Huai River basin, grass weeds dominate, accounting for 60%-70% of the total weed count, broadleaf weeds account for 20%-30%, and sedge weeds account for about 10%.

Grass weeds: large crabgrass (Digitaria sanguinalis), goosegrass (Eleusine indica), green foxtail (Setaria viridis), barnyardgrass (Echinochloa crus-galli), Kentucky bluegrass (Poa annua), etc.

Broadleaf weeds: three-seeded mercury (Acalypha australis), redroot pigweed (Amaranthus retroflexus), livid amaranth (Amaranthus blitum), purslane (Portulaca oleracea), velvetleaf (Abutilon theophrasti), field bindweed (Convolvulus arvensis), Japanese false bindweed (Calystegia hederacea), Asiatic dayflower (Commelina communis), lambsquarters (Chenopodium album), feather cockscomb (Celosia argentea), lambsquarters, small goosefoot (Chenopodium serotinum), morning glory (Ipomoea), thistle (Cirsium), etc.

Sedge weeds: purple nutsedge (Cyperus rotundus), etc.

When is the best time to apply herbicides in peanut fields?

The optimal application period for peanut herbicides is the 2-4 leaf stage of the weeds. If the weeds are too small, some will still emerge later; if the weeds are too large, they have strong resistance and will not be completely killed.

Do not spray during the high-temperature midday period, for two reasons: first, evaporation is too fast and the effect is poor; second, to prevent heatstroke and ensure your own safety. Generally, choose to spray before 10 a.m. or after 4 p.m.

Which post-emergence herbicide for peanuts is good?

1. Quizalofop-p-ethyl

Mode of action: It is absorbed through the stems and leaves of weeds and conducts both upward and downward within the plant, accumulating at the tips and intercalary meristems, inhibiting fatty acid synthesis in cells and causing the weeds to die.

Targets: It has excellent control efficacy against grass weeds in broadleaf crop fields.

Application method: Spray on stems and leaves at the 3-5 leaf stage of grass weeds.

Precautions: High humidity in the air and soil favors the absorption and translocation of quizalofop-p-ethyl by weeds.

2. Clethodim

Mode of action: After application, it is rapidly absorbed by the stems and leaves of grass weeds and translocated to the stem tips and meristems, inhibiting meristem activity, disrupting cell division and ultimately causing weed death.

Targets: It has a special effect on most annual and perennial grass weeds and is safe for dicotyledonous crops.

Application method: Spray treatment at the 3-5 leaf stage of weeds.

Precautions:

1. Timing the application correctly is crucial; clethodim has slightly poorer control efficacy on weeds before the 3-leaf stage and after the 5-leaf stage;

2. It has no pre-emergence knockdown effect on weeds. Note the influence of climatic conditions on efficacy: under drought, high temperature or low temperature, stomata close in large numbers and the cuticle thickens, all of which are unfavorable to the absorption of the herbicide by weeds.

3. In summer, choose to spray in the early morning or evening to favor absorption of the herbicide and expression of efficacy.

3. Bentazone

Targets: Controls broadleaf weeds and sedge weeds; it is ineffective against grass weeds.

Application method: Spray the weeds at the 2-5 leaf stage of peanuts.

Precautions:

1. Because this product acts mainly by contact action, the weed stems and leaves must be thoroughly wetted when spraying;

2. Hot, clear weather favors the expression of efficacy, so try to apply on hot sunny days; if used in drought, waterlogging or when temperatures fluctuate greatly, the effect is poorer and it easily damages the crop.

4. Oxyfluorfen

Mode of action: It enters the weed plant through the coleoptile and mesocotyl, with less absorption through the roots. This herbicide only exerts activity under light conditions, generating compounds toxic to plant cells that accumulate and take effect.

Targets: Controls annual monocotyledonous and dicotyledonous weeds; it is ineffective against narrow-leaf or perennial weeds.

Application method: Pre-emergence application requires a larger dose and gives poorer results, so post-emergence spray treatment is generally used.

Precautions:

1. Do not arbitrarily increase the dosage; after spraying, if temperatures are too high or too much herbicide contacts the crop locally, burn spots of varying degrees will appear. Because it has no systemic translocation action, the crop recovers after 10-15 days without yield reduction;

2. Use proper application techniques; for manual application, it is best to choose a fan nozzle and spray along the rows to avoid heavier herbicide damage caused by repeated application;

3. Choose the dosage according to the specific situation; for sensitive weeds, use the lower limit of the recommended dosage;

4. It only exerts efficacy under light conditions, so apply on sunny days.

5. Fomesafen

Mode of action: It can be absorbed by weed roots and leaves, causing them to rapidly wilt and die.

Targets: Controls broadleaf weeds and purple nutsedge, and also has a certain efficacy against grass weeds.

Application method: Spray treatment at the 1-3 compound leaf stage after peanut emergence and the 2-5 leaf stage of weeds.

Precautions:

1. Under adverse conditions such as field drought, peanut leaves may suffer some damage, with severe cases showing temporary wilting, but they can recover to normal within a week;

2. Fomesafen has a long residual effect in soil, so the dosage must be strictly controlled; sensitive subsequent crops are prone to herbicide damage, so choose safe subsequent crops.

6. Lactofen

Mode of action: Weeds absorb the herbicide through stems and leaves, which destroys cell membranes and causes the weeds to wither and die.

Targets: Controls broadleaf weeds.

Application method: Spray treatment before the 4-leaf stage of weeds.

Precautions: When temperature and soil moisture favor weed growth, efficacy is high. Lactofen has relatively poor crop safety, and varying degrees of herbicide damage will appear after application, but leaves that grow out later develop normally.

Common herbicide formulations for peanut fields

1. Quizalofop-p-ethyl + fluoroglycofen-ethyl: The price is very cheap, but weeds tend to rebound, and it is also ineffective against purple nutsedge;

2. Quizalofop-p-ethyl + fomesafen: The price is a bit more expensive than the first, but rebound is less likely; it is likewise ineffective against purple nutsedge. Note here that data show that using this formulation in the north easily causes herbicide damage, while it is relatively stable in the south.

3. Quizalofop-p-ethyl + bentazone: The price is higher than the above two, and it mainly targets purple nutsedge, but the amount should be appropriately increased; there will be no residue, and the effect on other weeds is average.

4. Quizalofop-p-ethyl + bentazone + acifluorfen: A three-way mixture. First, regarding efficacy, it is certainly better than the above two-way mixtures, with good effects on common weeds in peanut fields as well as purple nutsedge, and no residue. The only difficult thing to accept is the price, which can be 2-3 times more expensive than commonly used ones.

5. Quizalofop-p-ethyl + bentazone + fomesafen: Also a three-way mixture, with good weed control efficacy, but compared with point 4, this formulation can also be used on soybeans, meaning it is a herbicide suitable for both peanuts and soybeans; likewise, the price is not low.

Precautions for using herbicides in peanut fields

1. When mixing the herbicide, remember to dilute it twice. The specific method: pour the herbicide into a bucket (or sprayer tank), first add part of the water to dilute it, and after it is well diluted, add a large amount of water. The purpose of doing this is to make the herbicide solution more uniform, so that in the same field one patch will not suffer herbicide damage due to a high dose while another patch has weeds that do not die.

2. When there is standing water in the field or rain or dew on the peanut leaves, do not spray herbicide. Why? For fear of herbicide damage. When there is water on the peanut leaves, after the herbicide is sprayed, large water droplets form and then flow into the heart leaves. At this time, the herbicide concentration in the heart leaves is too high, very easily causing herbicide damage.

3. Do not spray herbicide when the seedlings are weak. What are weak seedlings? Plants that are short, yellowed and wilted, possibly caused by seeds, insect pests, diseases or other reasons. No matter the cause, do not spray herbicide at this time, because the peanut seedlings themselves are already weak, and once the herbicide is used poorly, herbicide damage is unavoidable.

4. Watch out for drift. For example, if corn, vegetables, sesame or other crops are planted nearby, and you spray on a windy day, the wind blows the herbicide solution onto the neighboring crop, causing herbicide damage to that crop; then just wait for your neighbor to come asking for compensation.

Pay attention to the weather when applying

Watch the weather. Because temperature affects both the activity of the herbicide and the ability of the crop to absorb it, when the weather is poor and the temperature is low, use the upper limit of the dosage; when the weather is good and the temperature is high, use the lower limit of the dosage.

Pay attention to the seedling condition when applying

Watch the seedling condition. Decide whether to apply based on the seedling condition; thin and weak seedlings should not be sprayed, otherwise herbicide damage will occur.

Pay attention to the weed condition when applying

Watch the weed condition. Investigate the weeds clearly: mainly grass weeds or broadleaf weeds, the size of the weeds, etc. Choose the right herbicide variety and treat the right target, so as to achieve high weed control efficacy; for larger weeds, appropriately increase the dose.

Three accuracies and five don'ts for using herbicides in peanut fields

Three accuracies

1. The application time must be accurate. Based on the weed-killing mechanism of the herbicide, strictly control the application time.

2. The application dosage must be accurate.

3. The area of the sprayed field must be accurate. When controlling grass weeds and others during the peanut growing period, there are concepts of accurate time, area and dosage. Otherwise, the deserved weed control effect will not be achieved, or the crop will suffer herbicide damage.

Five don'ts

1. Do not apply when seedlings are weak or collapsed.

2. Do not apply when there is standing water in the field.

3. Do not apply when the poisoned soil is too dry or the field soil is too dry.

4. Do not apply during heavy rain or when there is dew or rainwater on the leaves.

5. Do not apply in leaky fields.