Herbicides Used On Plants: How They Work & Examples

Herbicides are a type of chemical that can be used to kill plants. They can be used on crops, lawns, and gardens. Herbicides work by either preventing the plant from forming essential proteins or by disrupting the way those proteins are put together. Some herbicides are also used as defoliants, which means they will cause leaves to fall off trees before they can produce seeds. Some common examples of herbicides include Glyphosate, Atrazine, and 2,4-D.

Herbicides come in many different forms, including solid pellets and liquids. Some herbicides must be ingested by the plant to be effective, while others can be absorbed through the leaves or roots. Some will kill only broadleaf weeds, while others will kill both grasses and broadleaf weeds. Most herbicides work by disrupting photosynthesis in the leaves or roots of a plant (or both).

Herbicides are chemicals used to kill weeds (unwanted plants) that tend to compete with the grown crops. Herbicides can be selective or non-selective. Each of these groups can be sub-divided into three namely;

  • Contact
  • Systemic
  • Residual

Selective Herbicides

These are weed killers which by their chemical composition are capable of acting bio-chemically on either broad-leaved weeds or grasses. They are used predominately in monocropping situations. However, when these herbicides are used in high concentrations, they tend to have phytotoxic effects on cultivated crops. Selective herbicides that kill grasses only are Alachlor, Pendimethalin, etc. also those that kill broad leaves weeds only are Atrazine, Imasaquine, etc.

A selective pre-emergent herbicide kills weeds as they germinate from their seeds, but leaves an established lawn safe to continue thriving. Broad-leaf weeds are easily controlled with a selective post-emergent herbicide as they are much more biologically diverse from your grass lawn. They are targeted at killing broadleafs while leaving grass plants to thrive.

How Selective Herbicides Work

Selective herbicides are designed to work in a particular way: they target specific plants while allowing other plants to grow. They work by targeting specific metabolic processes that plants rely on to survive. Not all plants have the same metabolic processes, so by using a selective herbicide that is safe for your plants or lawn, you can target and eliminate specific weeds without risking your lawn.

Selective herbicides work by interfering with the plant’s ability to absorb nutrients, damaging the plant’s roots and leaves. This makes it harder for the plant to grow and compete with other plants around it.

Selective herbicides work by inhibiting a plant hormone called auxin. This hormone causes cells to grow and divide, which produces new plant growth. Inhibiting auxin allows selective herbicides to kill the targeted plant while leaving nearby plants unaffected.

Some selective herbicides are applied only when the soil is moist (such as post-emergent grass control), while others are applied when the soil dries out (such as pre-emergent weed control).

In addition to nonselective herbicides, there are also selective herbicides that target certain plant parts or stages of growth. These can be used alone or in combination with nonselective herbicides to create an effective weed management system that works well on a variety of crops.

For example, Tenacity Herbicide is a herbicide that controls broadleaf weeds, white clover, plantain, capeweed, cat’s ear, and creeping oxalis. It is also suitable for use on zoysia grass, kikuyu grass, couch grass, and buffalo grass.

Examples of selective commercial herbicides are:

#1. AXIAL 045EC: this is the first of a family of tailor-made cereal grass weed solutions to be introduced to growers globally. It has been developed for worldwide use in both wheat and barley and offers unrivaled crop tolerance. It is highly compatible with many broadleaf herbicides.

#2. Turflon Ester Ultra: This is a post-emergent herbicide that works best on broadleaf weeds and vines such as kudzu and ivy.

#3. Battleship III Herbicide: This is a selective post-emergent herbicide that contains Triclopyr, Fluroxypyr, and MCPA and contains no 2,4-D for cool & warm-season grasses.

#4. DUAL GOLD 960EC: is another pre-emergence herbicide that can be used to control annual grass weeds and some annual broad-leaved weeds in pulses, maize, and Sugarcane. It exhibits excellent selectivity with superior safety on a wide range of crops.

#5. T-Zone SE: This selective herbicide contains several active ingredients; this makes it cover a wide spectrum of tough weeds. The Triclopyr component kills ground ivy, wild violet oxalis, and wild blackberry. The Sulfentrazone chemical is responsible for the rapid weed elimination of species like spurge, white clover, and dandelions. The 2,4-D present targets the growth regulator of plants causing curling and twisting of the weeds, which leads to the death of the plant. Dicamba, the fourth component, is responsible for inhibiting the growth of tough weeds as it reaches the leaves and roots.

#6. FUSILADE FORTE 150EC: is a superior post-emergence grass weed herbicide that is used in fruits and vegetables. Fusilade Forte is applied when weeds are between the 2- 8 leaf stage. Fusilade Forte kills all germinated Grass weeds and is able to select a wide variety of vegetables and fruits. It gives all-season grass weed control eliminating the need for manual weeding.

#7. LUMAX 537.5SE: is a herbicide for pre and post-emergence control of grasses and broad-leaf weeds in maize and sugarcane. It can be applied as pre or post-emergence of both the weed and the crop.

#8. TRAXOS 045EC: This is another effective post-emergence herbicide for the control of annual grasses in wheat. It is safe for the crops and environment due to the Safener.

#9. Tenacity Herbicide: This is an effective systemic selective pre and post-emergent herbicide that controls broadleaf weeds and grasses in cool & warm-season turf.

#10. SedgeHammer Herbicide: This is another selective post-emergent herbicide for the control of nutsedge and other weeds in turf-grass and landscaped areas.

Other active ingredients are:

  • Basamaize for maize.
  • Ronster for rice.
  • Galex for cowpea, soyabeans, groundnut.
  • Bagram for rice and maize.
  • Cotoran for cassava.
  • Primextra for maize, cassava and yam. 
  • Diuron for yam and cassava.

Non-selective Herbicides

Non-selective herbicides are a class of herbicides that can be used in many different situations. They are most often used to control weeds in lawns, gardens, and other outdoor areas. These herbicides don’t discriminate between plants and other organisms, so they can kill both plants and weeds. Non-selective herbicides are also known as broadleaf weed killers.

These are otherwise known as total weed killers. They are used for weed control in any weed combination in the field, they will kill any kind of vegetation. An example is Glyphosate (Round-up).

Types of Non-Selective Herbicides

There are four main types of non-selective herbicides: Glyphosate (Roundup), 2,4-D, dicamba, and triclopyr. The first three are typically applied as liquid formulations while triclopyr is usually applied as a granular formulation. Each type has its own advantages and disadvantages depending on the situation you’re facing with your lawn or garden.

#1. Glyphosate: a broad spectrum, systemic herbicide that controls annual and perennial weeds, grasses, brush, and woody brush. Glyphosate can be used on both cropland and non-cropland sites. It is sold under the trade names Roundup, Rodeo, and others.

#2. 2,4-D (or dicamba): a selective plant killer that has been used for decades as a broadleaf weed control agent. It works by inhibiting the production of an enzyme called acetolactate synthase which is essential for photosynthesis. It can be applied to a wide range of crops including soybeans, corn, cereals, and cotton. 2,4-D can also be used in hay fields as long as it is applied before flowering begins in order to prevent seed formation.

Difference Between Selective And Non-selective Herbicides

Selective herbicides are designed to kill only certain types of plants. For example, if you wanted to kill all the weeds in your lawn but not your grass, a selective herbicide would be the solution. Non-selective herbicides are designed to kill all plants and weeds.

Non-selective herbicides are often more effective on broadleaf weeds than on grasses because broadleaf weeds have more complex root structures that make it harder for them to absorb the chemicals.

Classification Of Herbicides By Mode Of Action

According to their mode of action, herbicides can be classified as:

  • Contact
  • Residual herbicides
  • Systemic Herbicides

Contact Herbicides

Herbicides are chemicals that kill weeds by contact, which means the herbicide moves into and affects only the part of the plant that it comes into contact with. Herbicides were the first type of chemical used to control weeds, and they still have a significant advantage over other types of herbicides when used correctly. They usually control small weeds with good coverage; however, some can also kill large Malva, Purslane, and some other difficult-to-kill weeds. These types of herbicides kill any vegetation or weeds immediately after application. They stop all biological activities.

Examples of contact herbicides are diclofop, dinoseb, diquat, and paraquat. Certain contact herbicides, like diquat and paraquat, are deactivated by soil particles. They must be mixed with clear water and applied directly to the vegetation.

Systemic Herbicides

Systemic herbicides are slow-to-action types whose effects are not noticed until a few days or weeks after application. They can be translocated to other parts of the plant. Their effect is a thorough but gradual killing of the most stubborn and perennial weeds. They have the ability to move around the transportation and translocation systems to achieve a total kill.

They alter the normal biological function of the plant by interfering with certain biochemical reactions. Thus, when applied to foliage or soil, they enter the plant and translocate to their site of action. Examples of translocated herbicides are atrazine, glyphosate 2,4-dichloro phenoxy acetic acid (2,4-D), and simazine. Systemic herbicides, like contact herbicides, also have diverse modes of action at the molecular level.

Residual Herbicides

These are soil-acting weed killers whose effects on weed control are primarily as photosynthetic inhibitors. They can have both pre and post-emergence activity; they are applied to the soil after cultivation and effectively control germinating weed seeds. Examples are simazine, Diuron, etc.

Classification Of Herbicides Based On Time Of Usage

PRE-PLANTING HERBICIDES: This can be a foliar; selective or non-selective herbicide, applied before the crop is planted. Examples are Glyphosate , Paraquat.

PRE-EMERGENCE HERBICIDES: These are applied in the soil before the emergence of weeds, immediately after cultivation e.g Galex  + Metolachar used for cowpea, Cotoran used for cassava, etc. You can buy any of these Pre-Emergence Herbicides For Weeds Control

POSTEMERGENCE HERBICIDES: These are applied after the emergence of weeds and can have both contact and systemic actions, but are usually selective so as not to have a phytotoxicity effect on the cultivated crops. Examples are Laddox in maize, Paraquat, Propanil, and Glyphosate.  

Read also: List Of Herbicides Used For Weed Control On Maize Farm

How To Apply Herbicides

There are several Herbicide application methods. Herbicides are a lot like fertilizer. They’re meant to encourage plant growth, and they can help you get the most out of your yard.

The first step in applying herbicides is to identify the type of herbicide that you’re using. This is important because different herbicides work best on different types of weeds.

There are two main types of herbicides: systemic and non-systemic. Systemic herbicides work by entering through the leaves and penetrating deep into the plant’s vascular system. Non-systemic herbicides are absorbed through the leaves and affect only the top few inches of a plant’s growth.

Systemic Herbicides:

Systemic herbicides are applied directly to plants with a sprinkler, sprayer, or backpack sprayer. They’ll need to be mixed with an appropriate amount of water before they can be applied to the ground or plant stems (which will need to be cut). To use these products, simply follow instructions on how much product you should use per area (usually about 10-20 gallons per acre).

Non-Systemic Herbicides:

Non-systemic herbicides can also be used for weed control but are typically applied as dry granules or pellets that are mixed into soils at a rate of 1 pound per 1000 square feet (about 1/2 lb/yd2). These products will need to be watered before they’re applied.

#1. Apply herbicides with a spreader sticker: This is the most common method of application, and it involves placing a sticker on the surface you’re treating, then spraying herbicide into the hole in the sticker. You can also use this method to apply mists to plants.

#2. Use a backpack sprayer: This is a sprayer that’s mounted on a stand so that you can spray herbicides at any angle or distance from your body while they’re still contained within the backpack. It’s usually more expensive than other types of sprayers, but it’s convenient if you want to apply relatively large quantities of herbicide without having to use lots of different nozzles and accessories (which could be difficult when using conventional sprayers).

#3. Use an air foamer: These are often used by professional gardeners who want to treat large areas with herbicides without having to move around too much, they’re often mounted on wheels or rails so that they can move around easily while spraying herbicides onto plants in different directions.

In conclusion,

Herbicides are chemicals that can be used to kill unwanted plants and weeds. They’re effective because they can kill plants that are growing in areas where they’re not wanted, such as lawns and gardens. There are several different types of herbicides and they work in different ways.

121 thoughts on “Herbicides Used On Plants: How They Work & Examples”

  1. Thank you. Very educating but I have a question which goes thus:'Are non selective herbicides like glyphosate also systemic and/or used as a pre planting herbicide or not'? And also,how do we know how/when to apply the herbicides based on its mode of action?

  2. I have also ran into that trouble of not using herbicide at preemergence stage on my cassava farm. It's about 3weeks already after planting and I have agreed to doing manual weeding anyway. But am also asked to use herbicide after manual weeding. How do I apply it? Can I do it myself? How long will it keep the weed away after application?

  3. Is it possible not to use manual weeding at all for cassava intercropped with maize, I mean using herbicides only. What can I do to prevent the plants from being damaged during postemergence application of herbicides

  4. Is it possible not to use manual weeding at all for cassava intercropped with maize, I mean using herbicides only. What can I do to prevent the plants from being damaged during postemergence application of herbicides

  5. Very good write-up and a nice job you are doing here. Keep it up. I just harvested my maize and I want to kill off the weeds before planting cassava. What is the best herbicide combinations I can use please?

  6. Thank you very much. It is very possible you use only herbicides on your cassava farm but it has to start from land preparation. After clearing, ploughing and harrowing your land, you plant. immediately after planting you apply pre-emergence herbicides. this will keep your land off weeds for about 3months. by then, your cassava plants would have grown taller and able to suppress the weeds. you can't totally eradicate the weeds but what you are required to do is to suppress them greatly.

    i hope this helps. thanks.

  7. My cassava farm was weeded going to 3 weeks ago now. That was the first weeding after planting. Can i still use atrazine now to keep weeds away for the next 2 to 3 month to reduce cost incurred if manual weeding is applied? Thanks

  8. Hi, please I've got a question. Can you Convince me why i should mix altrazine xtra force and contact herbicide grass cutter on a just planted cassava farm (two days ago) is it good to mix the two or not to mix them after. I need your urgent reply, please.

  9. Cover fliting is done when the crops are still very young; you just cover all the plants preferably with plastic bowl, just the portion of the crops and spray your field. what you are preventing is contact of the chemical and your crops. i hope this helps.

  10. Cover fliting is done when the crops are still very young; you just cover all the plants preferably with plastic bowl, just the portion of the crops and spray your field. what you are preventing is contact of the chemical and your crops. i hope this helps.

    • Pls what type of chemical can I used for pre emergency wed control on my farm with maize and cassava. And how many months can wed start to germinate after application.

      Pls another question goes thus; which types of cassava and maize variety is the best to give a good yield

  11. Pls i planted corn 2 weeks ago after plowing and am currently intercropping it wt cassava but i hv little weeds germinating around. Shld i just spray atrazine herbicide as am planting d cassava or spray afterd cassava has sprouted

  12. Plz I will like to know the selective chemical I can us for cassava.the farm has been hand weeded but the weed keep growing too fast.is there any chemical I can use to control the weeds?

  13. Weldone. I planted maize on my entire farm and cassava on half (bcos of stem shortage). I weeded 3 weeks ago. Now i want to plant d remaining cassava but weeds are up again. What chemicals do i use? 2 when do i apply it, b4 or after planting? Thanks

  14. Well sir I must say I enjoy reading your article. Pls what chemical can I use to kill the grass in front of my compound? No plants just only weeds. Pls tell me the name chemical and where to get it in lagos. I want a very strong chemical that will be able to kill all the grass. Thanks. Michael from Lagos.

  15. helo master quadri i really enjoy ur class how ever i cultivate entirely different crops compared to what every one has commented one , my plants are plantain, paw paw and pepper but i intend to plant plantain now and inter-cropped with cassava so i want to seek ur advice how do i go about the planting and when do i need to use herbicide or shld i separate the crops like i hv done b4 now and for my plantain hat is stand alone like 5 months now wch herbicides that is best for it to b used thanks

  16. Thank for your work here. Please am planning to cultivate pepper and water melon next season. Although they would be on different plots of land. Which herbicides can i use to adequately control weeds on these farms and should they be sprayed pre emergence?

  17. Thanks for your observation. Personally, am an advocate of organic farming, i sternly detest the use of chemicals, however, you would agree with me that some situations in farm require the use of chemicals. Chemical is very effective in controlling weeds and pest. Glyposate in unarguably the most recommended and most effective active ingredient in controlling weeds, that is why i tell people to use it. On the issue if its apparent danger, it has dosage farmers must adhere to. With the recommended dosage their apparent dangers are mitigated.

  18. Please I need your urgent help. I want to go into agriculture business for the first time and having 2acres which am planting cassava and maize, so I need procedure to follow in pre and post emergence in chemical method. Thanks

  19. Good morning, I have a plantain farm and I want to intercrop with watermelon, I have just weeded the place, whats the best herbicide to use and can I spray befor planing the watermelon or after planting the watermelon?

  20. Am in need of ur assistant and is there no any herbicides that will work for both maize and cassava for post planting herbicides. My farm was large and have used glyphosate with attrazine as pre planting herbicides but to my surprise after two weeks its look as if I didn't spray any herbicides. Then I apply labourers weeding which is hoeing in order to remove d broad leaves and d grasses but to my surprise the farm has also grow this same weeds and I used d farm last year which am using this yr again. Now am tired of weeding and initially I forgot to apply d maize herbicides b4 planting cassava. My question now is that haven't d agriculturist develop another herbicides for mixed cropping of cassava and maize or other herbicides which will kill any kind of herbicides on mixed cropping.

  21. for now, there is not herbicide for such. that is why it is recommended to apply herbicide immediately after harvest. you can con tact the admin for further assistance.

  22. I went to agrochemical dealers 4 pre emergence herbicideherbicide for late maize. I was given squash which contains 276 g of paraquat. When I asked the amount toto mix, I was asked to use 1 and half of the cup for 16L back sprayer. Pls hw right is that?

  23. Well done sir , could pre emergent chemical be used in un cultivated / plan land and be effective like that of cultivated land.

  24. Well done sir, please I was told that powdered chemical mixed with liquid one are effective in killing the weeds and their seeds. Can my crop seeds like maize and groundnuts be affected if I apply these chemicals two days after planting because I was told to apply first and wait for 10days before planting! Thanks.

  25. Well done sir, please can my crop seeds(maize and groundnuts) be affected if I apply powdered plus liquid chemicals like two days after planting. I was told to apply first and wait for 10days before planting. Thanks.

  26. Morning sir, pls, can my seedlings( maize and groundnuts) be affected if powdered chemical mixed with glyphosate are applied 1 or 2 days after planting? I was told to apply first and wait for 10days before planting. Thanks.

  27. Good evening sir. I applied force up herbicide on my farm of 21 days maise today. After getting home, someone told me that those maize will be destroyed. I didn’t spray on it but around it. Is it true? Thank you sir

    • To avoid waste of time and money, as early as possible tomorrow, go and plant another maize on the field to replace the 21st day old one because the will definitely die within a week, if you plan another one immediately, you were good to go.

  28. I read your article and quite educative, where can I get the basegram for rice and maize you mentioned in the article?

  29. Good Morning.

    I am about to plant plantain suckers and I want to know which herbicide to use and how it should be used.

    Should I apply before planting the suckers or after planting the suckers.

    How should I apply it? Will there be an effect on the plantain if the herbicide touches it when applying?


  30. Thanks for your article. It really enlighten me more about Agriculture. I’m new in farming. I just prepare about 10 acres of land for watermelon farming. Please which herbicide is the best to use before planting watermelon to keep weed away from the farm till harvest period. Pls I need your help urgent. Regard Paul.


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