Worldwide herbicide consumption is estimated at more than 2 million tons, representing half of global pesticide consumption. Today, these compounds, whether chemical or biological, play an essential role in managing weeds, which compete with crops for vital resources such as water, nutrients and light. Thanks to their use, farmers have been able to revolutionize agricultural productivity, maximizing yields and improving the efficiency of their cropping systems. However, the intensive use of herbicides has also brought with it significant challenges, including weed resistance issues and concerns about environmental impacts. In this publication, we will examine the main categories of herbicides, their key characteristics and emerging trends towards more sustainable use.

Definition and function of herbicides

Herbicides are designed to control or eliminate unwanted plants, commonly known as weeds, that interfere with crop growth and development. They act by interfering with critical plant metabolic processes, such as photosynthesis, protein synthesis or cell division, resulting in the inhibition of weed growth or death. This ability to specifically control weeds allows growers to effectively manage competition for resources, thereby increasing yields and reducing operating costs.

Classification of herbicides

1. According to its mode of action

The mode of action of a herbicide refers to the specific mechanism through which the compound acts on the target plant, which makes it a fundamental criterion for selecting the most suitable herbicide according to the type of weed and environmental conditions. In this context, it is important to consider the classification established by the Herbicide Resistance Action Committee (HRAC), which organizes herbicides according to their mechanism of action. This classification not only facilitates the identification of the most effective herbicides, but is also essential for effective resistance management, a key aspect to ensure sustainability in herbicide use. The rotation of products belonging to different HRAC groups significantly reduces the risk of weeds developing resistance, which, in turn, contributes to maintaining the effectiveness of treatments in the long term.

• Systemic Herbicides: These herbicides are absorbed by the leaves or roots and transported through the vascular system of the plant. Upon reaching critical tissues, they interfere with essential physiological functions, resulting in plant death. Their ability to completely eliminate the plant makes them particularly effective in the management of perennial and resistant weeds.
• Contact Herbicides: They act only on the parts of the plant that come into contact with the product. Due to their localized mode of action, they are most effective on annual weeds and require complete coverage to ensure treatment efficacy. These herbicides are useful in situations where fast and efficient control of emerging vegetation is needed.
• Pre-emergent herbicides: They are applied before weed germination, acting on emerging seeds or seedlings. Their main function is to prevent the establishment of new plants, which helps to reduce competition from the beginning of the crop cycle.
• Postemergent Herbicides: These are applied after weeds have emerged and are active. These herbicides are essential to control plants that are already established and can be crucial during critical stages of crop growth, where competition for resources is at its highest.

2. According to their selectivity

The selectivity of a herbicide refers to its ability to selectively affect certain plant species, while leaving others, usually the main crop, unharmed.

• Selective Herbicides: These are designed to eliminate specific weeds without damaging the main crop. This selectivity is critical in cropping systems where weeds have different biological characteristics than the crop. Selective herbicides allow precise weed management without compromising crop health.
• Non-Selective Herbicides: They affect any plant with which they come into contact. These herbicides are useful in land preparation or in areas where removal of all vegetation is required. Their ability to kill any green plant makes them powerful tools for land management and clearing specific areas.

Key characteristics of herbicides

When selecting a herbicide, several key characteristics must be considered that influence its efficacy and long-term impact on the agricultural environment.

• Persistence: The persistence of a herbicide refers to the length of time the compound remains active in the soil or on plants. Herbicides with high persistence may offer prolonged weed control, but also present risks of contamination and adverse effects on subsequent crops. Proper management of persistence is essential to minimize environmental impacts and avoid accumulation of toxic residues.
• Spectrum of Control: This aspect refers to the range of weed species that a herbicide can control. Broad-spectrum herbicides have the ability to control multiple weed species, while narrow-spectrum herbicides are designed to target a narrow group of specific species. The choice between these types depends on the type of crop and the diversity of weeds present in the field.
• Toxicity: Herbicide toxicity is a critical consideration for the safety of operators, consumers and the environment. Toxicity profiles include safety to humans, wildlife and soil microorganisms. The current trend is to develop herbicides with lower toxic profiles and rapid environmental degradation to reduce the risk of contamination.

Emerging trends in herbicide use

With increasing environmental concerns and pressure to improve sustainability, herbicide use is evolving in several key directions.

1. Development of More Targeted Herbicides: Advances in biotechnology are enabling the development of herbicides that act more precisely on specific metabolic processes. These products seek to reduce undesirable impacts on non-target plants and minimize weed resistance.
2. Rotation of Modes of Action: Rotating herbicides with different modes of action is a crucial strategy for preventing resistance in weeds. By alternating between herbicides with different mechanisms of action, selective pressure is limited. It also maintains long-term weed control efficacy.
3. Biological herbicides: Biological herbicides use natural organisms such as fungi and bacteria, as well as compounds of natural origin. For example, such as essential oils and pelargonic acid, which are gaining great interest. These products offer a more environmentally friendly approach and can be integrated into integrated pest and weed management systems, although their efficacy and availability are still evolving.
4. New Application Technologies: Precision agriculture, the use of drones, artificial intelligence and laser technology are revolutionizing herbicide application. These technologies allow for more precise dosing and uniform coverage, improving treatment efficiency and reducing environmental impact.

Future Prospects

Herbicides will continue to be fundamental tools in global agriculture, playing a crucial role in managing weeds and optimizing productivity. However, their intensive use raises significant concerns, such as weed resistance and environmental protection. To ensure sustainable use, it is essential to adopt practices such as rotating modes of action together with the development of more targeted and biological herbicides. In addition to the implementation of advanced application technologies. Innovation and appropriate regulation will be key to balancing weed control efficacy with environmental responsibility, thus ensuring a sustainable future for agriculture.