Precautions for Corn Herbicides_OASIS AGRO SCIENCE LTD (2023)

1.The best application time of post-emergence herbicides:

It takes 2-6 hours for the herbicides to be absorbed by the corn after spraying. Whether the weeding effect during this period is ideal is closely related to the temperature and air humidity.

When applied in the weather with high temperature and low humidity, due to high temperature and strong light, the herbicide evaporates quickly, which results in a significant insufficient absorption of it by the weeds, which affects the weeding effect and is also likely to cause phytotoxicity to the corn seedlings.

The best application time is after 6 pm, because the temperature is low and the humidity is high at this time, the herbicide stays on the weed leaf surface for a long time, the weed can fully absorb the herbicide, which can improve the control effect and it is not easy to cause phytotoxicity.

2.When can corn seedlings be sprayed with post-emergence herbicides?

Corn grows 3 to 5 leaves, and 2 to 4 leaf stage of weeds is the best, especially nicosulfuron mixed with 2,4-D butyl ester can not be applied after the 5 leaf stage of corn.

Spraying when weeds in the field are basically neat and most weeds are in 2~4 leaf stage. If the herbicide is sprayed too late, the weeding effect will be affected due to the enhanced weed resistance. When spraying, the air temperature should be 15~25℃, the air relative humidity should be above 65%, and the wind speed should be below 4m/s. Choose spraying equipment and nozzles according to requirements and apply drugs according to operation specifications.


One method summed up in practice is that, on the premise of sufficient dosage, relatively speaking,the more water the better. For example, it is recommended to mix 1 barrel of water with 1 bottle of herbicide to change it into2 barrels of water. This can make the land fully soaked and improve the effect.

Be sure to spray evenly.

The size of weeds

Many people think that the smaller the weeds, the less resistance, the better the weeding effect. In fact, it is not, because the weeds are too small and there is no area where the herbicide is applied. The best weed age is between 2 leaves and 1 heart stage to 4 leaves and 1 heart stage. At this time, the weeds have a certain area of application and the resistance is not strong, the weeding effect is better.

Since most of the post-emergence herbicide ingredients of corn are nicosulfuron, some corn varieties are sensitive to this ingredient and are prone to phytotoxicity. Therefore, corn fields that grow sweet corn, waxy corn, and Denghai series cannot be sprayed to prevent the occurrence of phytotoxicity. For new corn varieties, please test before promoting.

7 days before and after spraying herbicide, it is forbidden to spray organophosphorus pesticides, otherwise it is easy to cause phytotoxicity. However, it can be mixed with pyrethroid insecticides, and attention should be paid to avoid heart leaves when spraying, so as to prevent herbicides from pouring into them.

Matters needing attention in using post-emergence herbicides

1.Use according to the prescribed dosage, do not increase the dosage at will;

2.Using the "secondary dilution method", the mother solution is first prepared, and then mixed with water and sprayed evenly;

3.The suitable period for using post-emergence herbicides in corn is between the 2-5 leaf stage of corn. If sprayed at the 5-7 leaf stage, it should be used between rows of corn to avoid spraying it into the heart leaves;

4.Some post-emergence herbicides are sensitive to sweet corn, seed fields and inbred lines, so don’t use them. It should be used in strict accordance with the instructions or the use methods recommended by technicians;

5.Corn treated with organophosphorus pesticides is sensitive to post-emergence herbicide. The interval between the two is at least 7 days;

6.Use a motorized sprayer to spray, do not increase the dosage without authorization, and prohibit repeated spraying;

7.The sprayer used to spray organophosphorus pesticides should be cleaned;

8.Spraying after 4 pm will have a higher control effect. Avoid spraying in continuous high temperature weather (temperature over 35℃).

It rained after the corn was sprayed with the herbicide. Do I need to spray again the next day?

First of all, we do not recommend to use post-emergence herbicide twice.

But some users are afraid that the weeds have not been killed and want to spray again. What should we do?

1.It rains immediately after applying the herbicide;

2.Heavy rain or heavy rain lasts a long time;

3.There is no weed poisoning for a period of time after spraying the herbicide (3-5 days for broad-leaved weeds and 5-7 days for sharp-leaved weeds), and corn also grows normally.

When the above three conditions are met, the herbicide can be sprayed again.


1.The rain is not heavy and the duration is short;

2.It rains 6 hours after spraying the herbicide;

3.Weeds have been poisoned.

If the above 3 points are met, it is not recommended to respray the herbicide to avoid phytotoxicity.

Principles of mixing pesticides

1.No adverse chemical reactions (such as hydrolysis, alkali hydrolysis, acid hydrolysis or oxidation-reduction reactions) occur between the mixed varieties, and can maintain the efficacy or synergy, and will not affect the physical properties of the pesticides (such as emulsification, suspension rate) reduce);

For example, most organophosphorus pesticides cannot be mixed with Bordeaux mixture, lime sulfur mixture; powders cannot be mixed with wettable powders and soluble powders.

2.The mixed use of different varieties of pesticides can cause phytotoxicity to crops. For example, the mixed use of organophosphorus insecticides and propanil will cause phytotoxicity to rice, and the mixed use of Bordeaux mixture and lime sulphur mixture will easily cause phytotoxicity to crops;

3.After the pesticide is mixed, its toxicity cannot be increased to ensure the safety to humans and animals;

4.The mixing should be reasonable. For example, to control gramineous weeds in soybean fields, it is enough to use the sethoxydim and haloxyfop alone. If the two are mixed, it will neither increase the efficiency nor expand the control spectrum, which is considered unreasonable mixing;

The mixed use of pesticides is to improve efficiency and economic benefits, and should not increase costs.

5.Pay attention to the antagonism between different varieties of pesticides. For example, the mixture of bentazon and sethoxydim will reduce the control effect on gramineous weeds due to antagonism.

Can corn herbicides be mixed with pesticides?

For crops, pre-germination treatment mainly refers to the spraying treatment of soil before sowing (or before transplanting), or after sowing, before emergence of crops, so as to close and kill weeds that have not emerged.

Such herbicides in corn fields include acetochlor, metolachlor, atrazine, etc., which can control a variety of annual gramineous weeds and some small seed broad-leaved weeds in the field. If it is in three provinces of Northeast China, a mixture of herbicides such as 2,4-d butyl ester will be used to expand the herbicidal spectrum or increase the efficacy.

If no herbicide is applied in this period or the soil sealing effect is not good, you can choose to spray the stems and leaves of the emerged weeds with post-emergence herbicides, including nicosulfuron such as sulfonylurea.


It must be used in strict accordance with the technical points and precautions in the herbicide manual to avoid causing phytotoxicity.

It's best not to mix them, because they have different goals, one is weeds and the other is corn. Also, pesticides may contain organic phosphorus, which is easy to cause phytotoxicity when mixed with post-emergence herbicides.

Reasons why corn herbicides and insecticides cannot be mixed?

1.The respective ingredients are not clear. For corn herbicides, the mixture of nicosulfuron-containing herbicides and organophosphorus pesticides will cause phytotoxicity, that is, organophosphorus pesticides cannot be used within 7 days after the corn herbicides are used;

2.The spraying targets are different. The corn herbicide is mainly sprayed on the weeds to absorb the liquid to kill the weeds, while the insecticide is sprayed on the corn leaves to absorb the liquid to achieve the purpose of controlling pests.

When can the pre-emergence herbicide be used? Do I have to walk backwards when applying herbicides? Under what circumstances can the best sealing effect be achieved?

Pre-seedling herbicide, that is, the soil sealing treatment agent, is treated before the emergence of weeds, and a soil layer containing herbicides is formed in the topsoil of 2-3 cm. The weed seeds are also in this soil layer, and once they germinate, they absorb the herbicide solution and die. However, corn seeds are generally in 3-5 cm soil layer, protected by coleoptiles during germination, and hardly absorb herbicide solution (even if some are absorbed, corn itself has certain drug resistance), thus ensuring the safety of corn.

Pre-emergence herbicides refer to weed seeds before germination, not corn seeds.

The corn has emerged, can we use herbicides?

The answer is yes. From seedling emergence to 3-leaf stage, corn itself absorbs limited herbicide solution and has certain drug resistance, so it is possible to spray herbicide before seedling. During the 3-5 leaf stage, corn itself secretes zeatin, which can relieve the phytotoxicity of nicosulfuron, and has certain resistance to pre-emergence herbicides, so both post-emergence herbicides and pre-emergence herbicides can be used, but attention should be paid to the dosage of pre-emergence herbicides. After the 5th leaf stage of maize, the secretion of zeatin was reduced or stopped, and the drug resistance was also greatly reduced. Therefore, pre-emergence herbicides cannot be used after the 5-leaf stage.

According to the action mechanism of pre-emergence herbicide, it is to form a layer of herbicide soil layer, not just a herbicide film, so stepping on the ground has no effect on the formation of herbicide soil layer.

The efficacy of pre-emergence herbicides is mainly affected by soil texture, soil moisture, organic matter content, soil microbes and rainfall. Considering comprehensively, a 2-3 cm soil layer containing herbicides will achieve a good sealing effect, and the soil layer is too shallow, too deep or intermittent, which will cause poor sealing effect.

What are the ingredients and precautions of herbicides in the early stage after seedling?

The main active ingredients are nicosulfuron, mesotrione, topramezone, bromoxynil octanoate, MCPA-Na, fluroxypyr, atrazine, etc.

The properties and matters needing attention of nicosulfuron, mesotrione and atrazine are mainly introduced.

Nicotinsulfuron, a systemic and conductive herbicide, generally takes effect within 5-7 days, and weeds die in about 2 weeks. It prevents most of the weeds in corn fields, but it is not effective for abutilon. It is not safe for special corn such as sweet corn, sticky corn, pop corn, and field corn, so it cannot be used. The 3-5 leaves of corn can be sprayed throughout the field, and those containing safeners can be sprayed in the whole field during the 3-10 leaf stage. Use 7 days apart from organophosphorus pesticides.

Mesotrione, a contact herbicide, takes effect in 3 days, and weeds die in 7-10 days. Controls most of the weeds in corn fields, but is not effective against setaria. It has higher safety to all varieties of corn. It can be used in the 3-10 leaf stage of corn, with high safety.

Atrazine, a systemic and conductive herbicide, can either close weeds or kill weeds (2-4 leaf grasses). There is a long residual period in the soil, which will have residual phytotoxicity on the next cruciferous crops and vegetables. Compounding with nicosulfuron or mesotrione can expand the herbicidal spectrum of the two, improve the efficacy, and increase the safety to corn,and mixed with nicosulfuron and mesotrione, it can also eliminate the antagonistic effect of nicosulfuron and mesotrione.

Cyperus rotundus, a weed in the Cyperaceae family, has roots, three-sided stems, parallel leaf veins, no petioles, and no obvious nodes. Weed control belongs to broad-leaved weeds in science. The ingredient that has a special effect on it is Halosulfuron-methyl (75%WG 5 g/bucket of water), and it is also effective with MCPA-Na and Bentazon. High content of nicosulfuron can inhibit the growth of weeds, and mesotrione can only kill the above-ground parts of weeds to a certain extent.

Commonly used products such as Nicosulfuron+Atrazine, Mesotrione +Atrazine, Nicosulfuron+Mesotrione+Atrazine, it rains 6-8 hours after the application, and the effect is less affected.


What precautions should you take when spraying herbicides? ›

There is potential for getting the herbicide in your eyes, protect them with goggles or a face shield; when mixing or spraying herbicides, always protect your eyes. Wear a hat – protecting your hair and scalp reduces your chance for exposure.

What are the best herbicides for corn? ›

Featured Corn Herbicides
  • TriVolt™ Herbicide. The Results Speak for Themselves. Harness® Xtra Herbicide for Corn. ...
  • Balance Flexx Herbicide. Get powerful, flexible control that fights resistance. Harness® Max Herbicide. ...
  • Degree Xtra® Improved Crop Safety and Powerful, Long Lasting Grass and Broadleaf Weed Control.

How late can you spray dicamba on corn? ›

Corn Maturity Cutoffs for Herbicides
Postemergence Corn HerbicidesCrop Height CutoffCrop Stage Cutoff
Dicamba (Banvel, Clarity)8 inches (1 pt/A) or 36 inches (1/2 pt/A)5 leaf –
Distinct24 inches
Glyphosate – RR corn only30 inches8 leaf
Halex GT30 inches8 leaf
18 more rows
Jun 10, 2020

What is the best post emergence herbicide for corn? ›

If time gets away from you, or Mother Nature throws a curve ball, Halex® GT herbicide tank mixed with atrazine or dicamba is the best choice for one-pass post-emergence weed control in glyphosate-tolerant corn*.

What safety precautions should you take before spraying? ›

Before applying a pesticide (indoors or outdoors), remove children, toys and pets from the area and keep them away until the pesticide has dried or as recommended by the label. Remove or cover food during indoor applications. Don't spray outdoors on windy or rainy days.

Do you need to wear a mask when spraying herbicide? ›

A respirator is a form of personal protective equipment (PPE). You must wear a respirator anytime the pesticide label, California's rules, or your employer requires one. If the label tells you to “avoid breathing dust, vapor, or mist” and you cannot do this, you may also need to wear a respirator.

When should you not spray corn? ›

Corn herbicides

Most prohibit applications after corn reaches V8 or 36 inches tall. Cadet – V2 until corn is 48 inches tall or prior to tasseling.

How do farmers keep weeds out of corn? ›

Tilling the soil before planting helps control certain weeds. After the weeds and corn have begun to grow, some farmers will cultivate their corn. They drive their tractors and cultivators through the field and the cultivator disturbs the soil between the rows of corn and kills the weeds.

Is 2,4-D safe for corn? ›

Because persistence of 2,4-D in the environment is relatively short, there is little concern about residual effect on crops grown in rotation with corn or groundwater contamination. 6. Many species of broadleaf weeds are controlled by 2,4-D.

Will corn recover from herbicide damage? ›

If injury is not severe, most times corn will recover when growing conditions become favorable for growth. Herbicides control plants in different ways.

What time do you spray corn for weeds? ›

On this episode of RealAgriculture Corn School, Sikkema notes that spraying Liberty at noon compared to midnight can increase yield by up to 50 bu/ac. While mid-day spraying does offer the best control, it does present some risks. Research also reveals that weed control and crop injury tend to follow the same line.

When should you not spray dicamba? ›

Never spray from sunset to sunrise. Avoid the hour after sunrise and the hour before sunset. Most inversions (and nearly all strong inversions) occur during these hours or at night. Never spray in winds below 3 mph.

What is the new herbicide for corn? ›

Corn farmers will have another option in the fight against tough-to-control weeds. BASF has announced Surtain, a new corn herbicide that the company hopes to be available for the 2024 growing season. Wade Firestone, US Crop Product Manager with BASF says Surtain provides growers with unmatched weed control.

What do farmers spray on corn before harvest? ›

Conventional farmers spray glyphosate on genetically engineered corn, oats, soybeans and wheat before it is harvested. Consumers also use glyphosate on their lawns and gardeners. Both the nature and severity of human health impacts following exposures to glyphosate herbicides are unknown.

What is a natural herbicide for corn? ›

Corn gluten meal is a powdery byproduct of the corn milling process. Originally used as a supplement in hog feed, corn gluten has become a common organic alternative to synthetic chemical herbicides.

What are 3 precautions before using a chemical? ›

Always carry chemicals in approved containers. Always wash your hands after using any unsafe material. Store materials properly, as directed on their labels. Flammable chemicals should be stored in a cool, dry place away from heat and sunlight.

What are three precautions you should follow when handling chemicals? ›

General rules for handling chemicals
  • Do not return chemicals to their original packaging. ...
  • Keep chemical containers closed. ...
  • Never use a wrong or an unmarked reagent. ...
  • Never put spatulas, stirrers or other objects into a storage container for chemicals.

How long after spraying is it safe? ›

If possible, remain inside or avoid the area whenever spraying takes place and for about 30 minutes after spraying. That time period will greatly reduce the likelihood of your breathing pesticides in the air.

Do N95 masks protect against pesticides? ›

PPE is designed to protect vulnerable body parts from specific hazards, for example, chemically resistant gloves are used to protect the skin on your hands from pesticide exposure, while an N95 respirator protects the mouth and nose from particles including small particle aerosols and large droplets (only non-oil ...

How long does it take for herbicide to wear off? ›

Depending on the type of herbicide and the level of concentration in the soil, persistent herbicides can last anywhere from several months to three or more years before completely breaking down into inert compounds.

Is herbicide safe after it dries? ›

Pesticides used for lawn care are indeed safe after they dry. They do stay in the grass for about two days after treatment. If you have pets, make sure to wipe their paws each time they go out on the lawn for the next few days after treatment. Also, wipe their coat before you allow them to enter your house.

Should you water corn at night? ›

It is particularly imperative not to water the corn patch by giving the entire area a sprinkling every night, for reasons detailed below (needs scroll to below).

What temperature kills corn plants? ›

Temperatures at 28 degrees F or less for a few hours can be lethal to the plant. The growing point of a young corn plant can be injured or killed at these temperatures. Living plant cells contains water. Temperatures below 28 degrees F cause ice crystals to form in the plant cells.

At what temperature does corn stop growing? ›

Growing Degree days are a daily accumulation of heat for crop growth. Corn does not grow when temperatures are below 50°F, and temperatures above 86°F do not increase plant growth rate.

Why do farmers leave one strip of corn? ›

Standing Strips: These strips were left because the corn was chopped. Some were left because the corn was infected with Aspergillus, which can produce aflatoxin and affect quality.

What is the #1 method of controlling weeds in crops? ›

Hand-hoeing or hand-pulling of weeds is always a part of crop management because cultivation does not remove all of the weeds. In some crops there may not be any other method of control. By removing the few remaining weeds in the crop, not only will there be less competition, but fewer weed seeds will be produced.

Why do farmers leave a strip of corn when harvesting? ›

Leave some of the corn stalk standing at harvest.

The standing residue allows good air movement down to the soil surface, encouraging faster breakdown of the residue.

Can I use Triple 13 on corn? ›

“Corn loves fertilizer as much as a pig loves to eat corn,” said AgCenter program assistant Bobby Williams. When preparing a garden for corn, apply 4-6 pounds of 13-13-13 fertilizer per 100 feet of row one to three weeks prior to planting.

What is the best fertilizer mix for field corn? ›

An economical, high-quality, complete fertilizer containing N and P can work as a starter fertilizer. In general, a fertilizer with a high P ratio (1-2-1, 1-3-1, etc.) in a highly water-soluble form and combined with ammonium nitrogen can be used. If applying in-furrow, recommended rates are 4 to 5 gallons per acre.

What is the best fertilizer mix for corn? ›

The fertilizer used as a starter should contain a small amount of nitrogen; most, if not all, of the recommended phosphorus; and possibly some potassium. Thus, a good starter fertilizer might range from a ratio of 1-4-0, 1-3-1, 1-3-3, to 1-1-1, depending on the rate of fertilizer required.

What PPE should you wear when using herbicide? ›

PPE includes:
  • respirators.
  • chemically impervious gloves and footwear.
  • washable coveralls and hats.
  • goggles or face shields.
Nov 3, 2021

How long after spraying herbicide is it safe? ›

Many companies that use these chemicals warn that people should stay away from sprayed surfaces for six to 24 hours.

What are the health effects of herbicide exposure? ›

Examples of acute health effects include stinging eyes, rashes, blisters, blindness, nausea, dizziness, diarrhea and death. Examples of known chronic effects are cancers, birth defects, reproductive harm, immunotoxicity, neurological and developmental toxicity, and disruption of the endocrine system.

What are the health risks of herbicides? ›

Long-Term Health Risks
  • Cancer. Some studies suggest glyphosate may be linked to cancer. ...
  • Liver and kidney damage. Glyphosate may affect your kidney and liver. ...
  • Reproductive and developmental issues. ...
  • Risk for pregnant women and children.
Apr 26, 2021

What mask to use when spraying herbicide? ›

Gas masks are usually full-facepiece respirators with one filtering canister. The full facepiece protects the eyes, nose, and mouth and provides a better seal than a half facepiece. The canister will last longer than chemical cartridge respirators when continuously exposed to some pesticides.

What respirator should I use for herbicides? ›

(APF = 10) Any particulate respirator equipped with an N95, R95, or P95 filter (including N95, R95, and P95 filtering facepieces) except quarter-mask respirators. The following filters may also be used: N99, R99, P99, N100, R100, P100.

What are some PPE needed when you spray the crops? ›

Wear PPE When Using Pesticides
  • Gloves. Your hands and forearms get the most exposure from pesticides. ...
  • Aprons. The label may require a chemical-resistant apron when mixing and loading a pesticide. ...
  • Footwear. ...
  • Coveralls and Chemical-resistant suits. ...
  • Headgear. ...
  • Protective Eyewear. ...
  • Respirators.
Jul 16, 2019

How long do you have to stay off your yard after spraying for weeds? ›

Wait 24 to 48 hours after applying the herbicide to mow. Hold off on watering as well. Children and pets should be kept off the area for at least one day. If weeds pop up again after you mow, wait three to five days before spraying the herbicide again to let the leaves grow back.

How do you use herbicides safely? ›

How to Safely Spray our Herbicides
  1. Never allow the spray to drift.
  2. Never mix the herbicides with another product unless recommended on the label.
  3. Allow the spray to dry completely.
  4. Wash up thoroughly once you're done.
Apr 16, 2020

What happens if you breathe in herbicide? ›

People who breathed in spray mist from products containing glyphosate felt irritation in their nose and throat. Swallowing products with glyphosate can cause increased saliva, burns in the mouth and throat, nausea, vomiting, and diarrhea. Fatalities have been reported in cases of intentional ingestion.

What is the most toxic herbicide to humans? ›

Paraquat is highly toxic to humans; one small accidental sip can be fatal and there is no antidote.

What are highly toxic chemicals used in herbicides? ›

Paraquat is a toxic chemical that is widely used as an herbicide (plant killer), primarily for weed and grass control. In the United States, paraquat is available primarily as a liquid in various strengths.

Is herbicide fatal to humans? ›

All chemicals, including herbicides, are potentially hazardous to human health. However, a basic principle of toxicology is that "the dose makes the poison".

What are long term side effects of herbicides? ›

The most direct effects of herbicide pollution are decreased condition, growth, and reproduction, and increased mortality, of plants (i.e., macrophytes, periphyton and phytoplankton).

What disease is caused by herbicides? ›

Long term pesticide exposure has been linked to the development of Parkinson's disease; asthma; depression and anxiety; attention deficit and hyperactivity disorder (ADHD); and cancer, including leukaemia and non-Hodgkin's lymphoma.


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