herbicider

Herbicider, more commonly spelled herbicide, is any chemical substance or biological agent used to suppress or destroy unwanted vegetation, especially weeds. Herbicides are applied in agricultural production, horticulture, turf management, and urban landscapes to reduce competition for water, nutrients, and sunlight; in some cases they are used to control invasive plant species or to prepare land for planting.

Herbicides can be selective, targeting specific plant species while sparing crops, or non-selective, affecting a broad range of plants. They may act systemically, moving within the plant after absorption, or as contact herbicides, killing only plant tissue they touch. They are also categorized by timing: pre-emergence herbicides prevent germination, while post-emergence herbicides kill established plants. Residual or persistent herbicides continue to act after application, influencing future weed pressure.

Common formulations include liquid concentrates, emulsifiable concentrates, flowable suspensions, granules, and ready-to-use products. Application methods vary by formulation, crop system, and target weeds, typically involving spraying or spreading on soil or foliage. Labeling provides instructions on rates, timing, safety, and environmental precautions.

Regulatory oversight exists in most countries, requiring registration with agricultural or environmental authorities and adherence to label directions. Proper handling, storage, and use reduce risks to humans, wildlife, water, and non-target plants. Potential environmental effects include toxicity to aquatic organisms, soil microbiota, and development of herbicide resistance in weeds.

Resistance management emphasizes rotating herbicides with different modes of action and integrating non-chemical weed control methods. The modern herbicide era began in the mid-20th century with compounds such as 2,4-D and glyphosate, leading to widespread adoption in agriculture. As weed populations adapt, ongoing research aims to improve modes of action, safety, and stewardship.