herbicide

A herbicide is a chemical, biological, or microbial product used to control or suppress unwanted vegetation, typically weeds, in agriculture, horticulture, turf, and forestry. They can be applied to soil (pre-emergent) or to growing plants (post-emergent) and may act on contact or systemically. Selection depends on crop tolerance, weed spectrum, timing, and environmental considerations.

Herbicides are commonly categorized by selectivity (selective vs non-selective), timing (pre-emergent vs post-emergent), and mode of action (systemic vs contact). Selective products target certain weeds with minimal crop injury; non-selective products affect many plants. Pre-emergents prevent germination in the soil; post-emergents act on established weeds.

Common mechanisms include inhibition of amino acid synthesis (ALS inhibitors like imazapyr), inhibition of EPSP synthase (glyphosate), disruption of photosynthesis (atrazine), and growth regulation (2,4-D). There are synthetic herbicides and biological or natural-product options. Resistance can develop with repeated use, making integrated weed management important.

Regulation includes registration and labeling by national authorities, with safety, residue limits, and environmental risk assessments. Proper handling, personal protective equipment, and adherence to labels are emphasized. To limit resistance and environmental impact, modern weed management often combines chemical control with cultural, mechanical, and biological methods.