As a result of industrialization, a shift in attitudes, and increasing global demand for crops, farmers have turned to agrochemicals to improve and maintain our global food supply. Agrochemicals comprise a variety of products that can be classified into several types. Most people, however, are unaware of these classifications and typically refer to any product applied to plants or crops as “fertilizer.”
This generalization often leads to misinformation about what products can and can’t do, and can lead to misuse when products are used for purposes they aren’t designed for. To eliminate confusion, here’s a quick look at the differences between three main types of agrochemicals and how they function to improve our food supply.
One of the toughest challenges a farmer (or gardener) faces is controlling weeds. Reducing the infiltration of weeds into a crop helps ensure that nutrients and water are being used by the wanted crop, not being diverted to help weeds grow. While a homeowner or small farm may be able to manage weed control by physically removing weeds from their crops or garden beds, this is not a viable solution for commercial farming operations. They rely on herbicides to halt weed development and growth.
The development of precision herbicides over the last several decades has resulted in the ability to kill weeds without harming crops. This innovation is a result of specific targeting actions, known as “modes of action,” that describe the main ways herbicides work to kill or prevent weeds. These modes of action include preventing cell division, fueling uncontrolled growth to kill the weed, disrupting vital enzyme systems, and destroying cells and tissue within the weed. By selecting the mode of action that best targets the particular weeds encroaching on a crop, farmers can select the right herbicide for their needs. This, in turn, allows them to use fewer chemicals and less water, and have a lighter impact on the soil.
Similar to herbicides, insecticides are classified by the method they use to kill or prevent the reproduction of insects. They typically work via two modes: killing the insect outright or interfering with the insect behavior that destroys the plant. Insecticides may affect the nervous system of insects, either blocking or inhibiting enzymes that the insect needs to survive. Farmers typically administer insecticides to crops via contact, systematic, or residual applications.
Contact applications are administered directly to the insect, killing it without affecting the surrounding plants. Little residue remains after the insecticide is applied and the insecticide works almost immediately.
Systemic applications of insecticide are used for long-term pest control. The insecticide is applied and absorbed into the plant, and is passed to the insect when it feeds on the plant. Alternatively, some insecticides are eaten directly by the insect, killing them quickly. In either case, the insecticide works over the long term to control pest populations.
Residual applications are used to control insect populations in specific locations. The residue remains on the surface of the plant for a duration of time, maintaining the effectiveness of the poison.
Another major issue confronting farmers is fungus, which can cause devastating crop losses and harm the quality of the crop. Fungal diseases can be controlled by fungicides, which either kill the fungus causing the disease or inhibit the disease’s growth. To prevent the spread of disease in plants, however, fungicides must be applied before the disease occurs. Damage caused by fungus cannot be reversed or repaired, making the regular application of fungicide essential to maintaining crop protection.
Unlike insecticides and herbicides, which are often applied after insects and weeds appear, fungicide is primarily used in the prevention of disease. Similar to other agrochemicals, however, fungicides are classified by modes of action and application. There are both contact and systemic fungicides which function in the same general manner as other agrochemicals. Contact fungicides remain on the plant, while systematic fungicides are absorbed by the plant and work from within. The application method should be selected based on the needs of the farmer and the crop, with careful attention paid to each fungicide’s mode of action. Fungicides typically work via three modes of action: they interfere with the fungus’ energy production or respiration, damage cell membranes, or inhibit important enzymes the fungus needs to grow.
Agrochemicals are a billion-dollar industry that has revolutionized farming around the world. As the demand for crop production, stronger resistance to disease and insect infestation, and greater transportability continues to increase, the need for agrochemicals will grow as well. Understanding the various agrochemicals available allows farmers to use exactly what their crops need, while reducing the environmental impact. Overall, agrochemicals have allowed the world to produce more food more efficiently. Without the development of stronger, more effective agrochemicals, these gains in meeting the world’s demands would not be possible.