Farmers and ranchers use herbicides to control certain species of plants considered to be weeds or pests. Consisting of various chemicals, herbicides kill unwanted plants. The USDA classifies herbicides as chemical pesticides, with the majority of applications occurring within the agricultural sector. The proper usage of agricultural herbicides protects crops, while mitigating damage to the environment.
Herbicide methods in agriculture are noted as early as 146 B.C. when salt was used by the Romans in Carthage to eliminate the replanting of agricultural fields. The majority of early herbicides worked in a non-selective manner, killing all plants. In 1945, the British introduced 2,4-D as the first selective herbicide. Further innovations produced herbicides that work in numerous applications to both prevent and control weed growth. Manufacturers and researchers continue to introduce new herbicides featuring better results and less environmental impact.
The website 24d.org, an industry task force for the research of 2,4-D herbicides, considers weeds the main pest problem for food production. Weeds compete with crops and forage grasses for water, nutrients and space. The competition results in reduced crop yields and increased production costs. Herbicides help to reduce the labor and fuel consumption associated with agricultural production.
Producers choose an herbicide based on whether it is selective or non-selective. Selective herbicides, such as 2,4-D and Milestone, target specific types of weeds within a crop. For example, 2,4-D kills all broadleaf weeds, but does not damage wheat, corn or many types of forage grasses. The pest plants are eliminated, while the desired plant species is unaffected.
Non-selective herbicides kill all plants, regardless of type. For example, Roundup may be used to remove all plants growing in a specific area in preparation for a future planting.
Herbicides also work during two different stages of plant life: pre-emergence and post-emergence. Agricultural producers apply pre-emergent herbicides to a crop or grassland in order to control weeds before they emerge from the ground. These herbicides function to are implemented into the ground through irrigation or tilling. Pre-emergents prevent seeds from germinating and growing.
Producers apply post-emergent herbicides after they have sprouted and began growth. The exact timing of application depends on the crop, specific weed and the type of herbicide. The plant absorbs the chemicals, which then function to destroy the plant on a cellular level.
The Center for Food Safety reports that various pesticides used for weed, insect and plant pathogen control have adverse affects on the environment and human health. All herbicide labels should be carefully read before application, with all recommended application rates closely followed. Immediate dangers to those working with agricultural herbicides include severe irritation to the eyes, skin and lungs.