How Do Herbicides Affect Plants and the Environment?
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:
Selective Herbicides - They control a few specific species of weeds and have very little or no adverse effect on the desired crop.
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.
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.
Conclusion:
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.
FAQs on Herbicides: Types, Uses, and Side Effects
1. What are herbicides and why are they important in modern agriculture?
Herbicides, also known as weedkillers, are chemical substances specifically designed to control or eliminate unwanted plants (weeds). They are crucial in modern agriculture because they help maximise crop yield by removing weeds that compete with crops for essential resources like sunlight, water, and soil nutrients. This leads to healthier crops, reduced labour costs for manual weeding, and greater food production efficiency.
2. What is the main difference between a selective and a non-selective herbicide?
The main difference lies in their target specificity. A selective herbicide is designed to kill specific types of weeds while leaving the main crop unharmed. For example, 2,4-D is used to control broadleaf weeds in cereal crops. In contrast, a non-selective herbicide, like glyphosate, kills nearly all types of plants it comes into contact with and is used for clearing large areas of vegetation.
3. How are herbicides classified based on their application timing?
Herbicides are primarily classified into two groups based on when they are applied relative to the weed's growth stage:
Pre-emergent Herbicides: These are applied to the soil before the weed seeds germinate. They create a chemical barrier that inhibits the growth of young weed seedlings as they sprout.
Post-emergent Herbicides: These are applied directly to weeds that are already actively growing and visible above the ground.
4. What are some common examples of herbicides and what are they used for?
Several types of herbicides are used in agriculture. Some common examples include:
Glyphosate: A broad-spectrum, non-selective herbicide used for clearing fields before planting.
Atrazine: A selective herbicide used to control broadleaf and grassy weeds in crops like maize and sugarcane.
2,4-D (2,4-Dichlorophenoxyacetic acid): One of the oldest and most widely used selective herbicides for controlling broadleaf weeds in lawns and cereal fields.
Paraquat: A fast-acting, non-selective contact herbicide used to desiccate weeds quickly.
5. What are the potential side effects of using herbicides on the environment?
While beneficial for agriculture, improper use of herbicides can have negative environmental impacts. These include potential soil and water contamination through runoff, which can harm aquatic life. Herbicides can also affect non-target plants, including beneficial wildflowers that support pollinators, and can disrupt the local ecosystem by reducing biodiversity.
6. Is there a difference between a 'herbicide' and a 'weedicide'?
The terms are often used interchangeably, but there is a subtle distinction. 'Herbicide' is the scientifically accepted and broader term, referring to any chemical that kills or inhibits plant growth (from the Latin 'herba' for plant and 'caedere' to kill). 'Weedicide' is a more common or colloquial term that specifically refers to chemicals used to kill unwanted weeds. All weedicides are herbicides, but the term herbicide can encompass a wider range of plant control applications.
7. How is herbicide resistance different from herbicide tolerance in plants?
These two terms describe different biological phenomena:
Herbicide Resistance is the acquired, inheritable ability of a plant to survive a herbicide application that was previously effective. It occurs due to genetic mutation and selection pressure from repeated use of the same herbicide.
Herbicide Tolerance is the inherent, natural ability of a plant species to survive and reproduce after a herbicide treatment without any prior exposure or genetic selection. The plant species was never susceptible to that particular herbicide from the beginning.
8. How does a systemic herbicide work compared to a contact herbicide?
The primary difference is their mode of action within the plant. A contact herbicide kills only the plant parts it directly touches. It is fast-acting but may not kill the root system. A systemic herbicide is absorbed by the plant (through leaves or roots) and translocated throughout its vascular system (xylem and phloem). This ensures the entire plant, including the roots, is killed, which is more effective for controlling perennial weeds.
9. Why is it not advisable to use the same herbicide on a field year after year?
Continuously using the same herbicide creates immense selection pressure on the weed population. Any weeds with a natural, random mutation that allows them to survive the herbicide will reproduce, passing this trait to their offspring. Over several years, this leads to the evolution of a herbicide-resistant weed population, rendering the herbicide ineffective. Rotating herbicides with different modes of action is a key strategy to prevent and manage resistance.
