Scientific Definition and Regulatory Status
Under international agrochemical nomenclature and the Insecticides Act, herbicides are chemical agents that alter plant growth or destroy target vegetative tissues.
They are systematically classified according to their spectrum of activity, site of uptake, and timing of application.
- Selective herbicides: Eliminate target weed species without causing physiological damage to the standing crop
- Non-selective herbicides: Destroy all green plant foliage they contact indiscriminately
- Contact herbicides: Inhibit or destroy tissues only where direct spray droplets impact the foliage
- Systemic herbicides: Translocate basipetally or acropetally through plant vascular systems to eradicate root networks
Application Timing Windows in Farming
Timing herbicide application correctly is crucial for maximizing weed kill while preventing crop injury.
The three primary application windows correspond to crop and weed germination timelines.
- Pre-plant incorporation: Inverted into moist soil prior to crop sowing to control dormant weed seeds
- Pre-emergence: Sprayed onto soil surfaces after sowing but before crop or weed seedlings emerge
- Post-emergence: Sprayed over the crop canopy when weeds are actively photosynthesizing at early leaf stages
Resistance Management and Environmental Stewardship
Relying repeatedly on single chemical modes of action encourages the survival and proliferation of resistant weed biotypes.
Practicing Integrated Weed Management (IWM) by combining crop rotation, cover crops, and alternating herbicide classes maintains chemical longevity.
- IWM integration: Combine manual rogueing, cover cropping, and chemical rotation to delay resistance
- Spray calibration: Use flat fan nozzles at low operating pressure to maintain uniform coarse spray droplets
- Operator safety: Always wear personal protective gear including chemical gloves, face mask, and eye protection
Official source
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Central Insecticides Board & Registration Committee ↗Related on KisanPe
Common questions
What is the formal definition of an herbicide?
A herbicide is a chemical or biological substance formulated to suppress, control, or eliminate unwanted plant species known as weeds.
What is the difference between selective and non-selective herbicides?
Selective herbicides kill specific weeds while leaving the crop unharmed, whereas non-selective herbicides destroy all green plant tissue indiscriminately.
Why is nozzle selection important when applying herbicides?
Flat fan or floodjet nozzles produce coarse, even droplets that minimize spray drift and ensure uniform soil or foliar coverage.
General guidance, not personal advice. For your farm, ask your local Krishi Vigyan Kendra or agriculture officer.
More Crop Protection & Pesticides guides
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