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Introduction to Herbicide

Whether you are tending to your lawn garden or producing agricultural crops, you need to control weed growth to be successful in any of these endeavors. Weeds are valueless plants that grow wild on cultivated land that cause injury or have undesirable effects on the plants. There are many ways of controlling weed growth like mechanical, biological, cultural, and chemical. You might need one or all of these methods for an effective and environmentally-friendly weed control system.

For many years herbicides (chemical control of weeds) have been an essential tool for managing weeds in home landscapes and crops. With modern changes, many herbicides of today are selective and effective. These traits of some new herbicides, if used properly, can be less hazardous to the environment.

This article will give you the basics of what is herbicide, different types of herbicides, harmful effects of some of the herbicides like glyphosate herbicide, and a few widely used herbicides.

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What is Herbicide?

From the time the Green revolution started, herbicides have been in use for protecting cropland. Herbicides are a broad class of pesticides that hamper the growth of unwanted plants. They are chemicals that can control or manipulate undesirable vegetation. Herbicides are used widely in row-crop farming, where they are either applied before or after planting. Spraying herbicides prevents or minimizes other vegetation, maximizes crop production, and improves harvesting.

  • When used in wildlands, herbicides can increase the diversity of native species.

  • Herbicides used in agroecosystems can change the composition of the weed population.

  • Herbicides are chemicals with their set of adverse effects but they are still desirable over habitat loss, invasive species, and threat to biodiversity.

Types of Herbicides:

There are mainly two types of herbicides:

  1. Selective Herbicides - They control a few specific species of weeds and have very little or no adverse effect on the desired crop.

  2. Non-selective Herbicides - They are also commercially called total weed killers and are used for clearing wastelands, construction and industrial sites, railways and railways embankments. This type of herbicide kills the entire plant material, whatever it comes in contact with.

There are a few other ways to distinguish between different types of herbicides as outlined below:

  • Based on Persistence - This is also called the residual action which means how long the herbicide material stays in soil and remains active.

  • Based on Means of Uptake - This is a distinction between different herbicides based on what kind of plants absorb it; whether it is absorbed by only above-ground foliage through the roots, or there are other means.

  • Mechanism of Action - It defines how a herbicide acts to achieve its goal.

Difference Between Herbicide and Weedicide

Herbicides and Weedicides are both used to prevent unwanted vegetation in agriculture and home. The primary difference between the two is that herbicide stops the growth of plants whereas weedicides skill weeds.



They are designed to kill specific types of pests and are used mainly on plants.

They are sprayed in the field to kill weeds. They are sprayed on weeds at the time of their vegetative growth (before they completely blossom and produce seeds)

They are used mostly in industrial spaces, farms, waste grounds, and railways.

Weedicides do not have any negative effect on crops. They are sprayed in the fields with a sprayer by diluting them with water to get the desired concentration.

Some of the Widely Used Herbicides

  • Glyphosate Herbicide - This herbicide is applied to the leaves of plants which kills both grass and broadleaf plants. Glyphosate herbicide was first registered in the United States in 1974 and is to date the most widely used herbicide in the US. The sodium salt form of glyphosate helps in regulating plant growth and in the ripening of specific crops. It is applied largely in agriculture, forestry, gardens, and lawns. There are some products with glyphosate in it that can even control aquatic plants.

    • It is a non-selective herbicide which means it kills most of the plant.

    • It prevents the production of certain proteins in plants that are necessary for their growth.

    • Plants that have been treated with glyphosate herbicide turn yellow after 5 to 7 days of application, then they turn brown and die within 10 days.

    • If humans are exposed to glyphosate, it might cause mouth and throat burn, increased saliva, diarrhea, nausea, or vomiting. Glyphosate might cause fatalities if ingested intentionally. If ingested in small quantities, most of the herbicide in humans usually passes through the body in the form of feces or urine without changing into another chemical.

  • Atrazine Herbicide - This herbicide is used widely for row crops like sorghum, corn, and sugarcane. In some areas, atrazine herbicide is also used in industrial lawns. It controls grassy and broadleaf weeds.

    • Atrazine can enter waterways from row crops' agricultural runoffs and contaminate surface and groundwater. If atrazine is present in public or private water supplies in amounts more than the standard set by EPA (Environmental Protection Agency, U.S), it can lead to health problems in humans.

    • It may reduce primary production in aquatic communities as it inhibits photosynthesis. 

    • Atrazine has been linked with reproductive issues in amphibians and other forms of wildlife.

    • There is a current study going on to find potential carcinogenic and endocrine disruption effects of atrazine.

  • Sempra Herbicide - This herbicide was introduced in India by Dhanuka Agritech Ltd., and it is the first of its kind in India for controlling Cyperus rotundus. It is a selective, post-emergence, systemic herbicide made with WDG (Water dispersible granules) formulation. It can effectively control Cyperus rotundus from nuts in maize, wheat, barley, and sugarcane.

  • Gramoxone Herbicide - This herbicide has revolutionized the weed control mechanism by replacing the time-consuming, tedious chore of hand weeding. It is a non-selective, contact, and fast-acting herbicide used for controlling annual broadleaf weeds and fibrous-rooted grasses. It contains Paraquat as an active ingredient that gets deactivated when it comes in contact with soil (it rapidly binds to soil particles). Hence this paraquat herbicide has no negative impact on soil organisms or groundwater. It is used widely on cotton crops.


Herbicides are chemical substances that are used widely for controlling undesirable vegetation in crops and home landscapes. Though herbicides give quick results, chemical herbicides can have a negative impact on human health as well as wildlife. Therefore it is suggested to use greener and healthier ways to promote crop productivity. Before putting any herbicide in your soil, be sure to understand its contraindications and consult a professional who can do a soil test and determine the best course of action for your plants.

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FAQs on Herbicide

1. What is herbicide resistance and how is it different from herbicide tolerance?

Herbicide Resistance

Herbicide Tolerance

The acquired ability of a weed plant to survive a herbicide application that had previously been able to control the weed population is called Herbicide resistance.

The inherent ability of certain species to survive after herbicide application is called herbicide tolerance.

In this, there is a change in the response of weed to herbicide over time and the weed which was responding earlier stops responding after a time.

In this, the weed population has always been tolerant to the herbicide and there is no change in their equation over time.

  • Herbicide-resistant biotypes (plants within a species whose biological characteristics are uncommon in the population as a whole) are naturally present in the weed population at extremely low frequencies. 

  • These biotypes have a herbicide resistance mechanism to allow them to resist a herbicide.

  • Herbicide resistance is a genetic feature and can be passed from one generation to another.

  • The length of time before resistance kicks in weeds is dependent on:

    1. Herbicide mechanism of action

    2. Cultural practices

    3. Biology of weed species

    4. Frequency of herbicide usage

    5. Frequency of resistant biotypes within the weed species.

2. What is pre-emergent herbicide?

A)The word preemergence in weeds means “before the weeds emerge” (more importantly before they germinate). Pre-emergence herbicides work by preventing the establishment of seeds and not by killing seeds.

  • Pre-emergent herbicides stop the germinated weed seedling from establishing.

  • They achieve this by many means like inhibiting the growth of shoot, or root, or both.

  • This type of herbicide needs to be incorporated into the soil via irrigation or rainfall. They are effective only when they are present in the soil before weed seeds germinate.

  • Pre-emergent does not have any effect on seeds.

  • Pre-emergent herbicides stay in the soil for a while to prevent weed growth and later get degraded by soil microbes.