Herbicide is a substance that is toxic to plants, it is used to destroy unwanted plants. Herbicides belong to the chemical group of pesticides. Herbicides can be used in the form of organic chemicals or synthetic substances also called weed killers.

The ingredients used in herbicides:

  • Amine salt (trimethylamine)
  • Atrazine (ground water contamination, does not break down easily – carryover undesirable property of herbicide)
  • Clethodim
  • Clopyralid
  • Deicamba
  • Glufosinate ammonium
  • Flauzifop
  • Fluroxypyr
  • Esters
  • Glyphosate (Round up) (non selective and selective)
  • Imazapyr
  • Imazapic
  • Imazamox
  • Linuron
  • MCPA
  • Metalachlor
  • Meta Soium
  • Paraquat
  • Pelargonic acid
  • Pendimethalin
  • Piclorgam
  • Sethoxydim
  • Sodium chlorate
  • Triclipyr
  • Vinegar (Acetic acid)

Why use herbicide?

By killing unwanted plants or weeds, farmers have crops to grow and gardens look beautiful. Farmers and private households are exposed to weeds and the use of herbicides destroys these unwanted plants. Common weeds which herbicides destroy include: African boxthorn, African daisy, African lovegrass, Amsinckaia, Artichoke thistle, Blackberry, Bindi, Bonnseed, Caltrop, Chilean cestrum, English broom, Dandelion, Thistle and much more.

Have a read of our weed identification guide to see the full list.

Herbicide grouping

When describing herbicides, it can be grouped into selective or non selective herbicide. Selective herbicides are specific killing of weeds. For example there are herbicides which only kill broad leaf weeds and these are called selective herbicides.

Non selective herbicides destroy all plants the chemical comes in contact with. It is non specific for a weed. Non selective herbicides can kill crops, grass and weeds.

Types of herbicides

Herbicides can be grouped into 3 segments which are timing based. The time when herbicides are applied matters to how effective it will be. Herbicides can be:

Pre-plant: Preplant herbicide is applied to the soil before the emergence of the crop and weed. The key feature of preplant herbicide is the residual characteristic it has. The residual of the herbicide will stay and provide an extended protection against germination or emergence of weeds.

Pre-emergence: Preemergence herbicide is applied to the soil and timing is important for this type of herbicide. The herbicide affects and damages the cell structure of the seedling, it does not stop the seedling from activation however it kills the growth of the weed.

Post-Emergence: Is application of herbicide is applied after the weed has emerged from its seedling stage. Post-emergence are effective once the weed has grown and can be selective or non selective weed killer.

Application of herbicide

Herbicides can be applied to weeds by application to the soil or application to the weed. Spraying the herbicide on the soil or plant is the most common method of application.

Types of spraying

Spraying herbicide can include aerial spray, misters, blanket wipers, rope wick applicators, weed seekers, boom sprays, and back-pack sprayers.

Aerial spray

Aerial spray is a common way to apply herbicides to weeds. Farmers use aerial herbicides to control large areas of land in order to remove weeds. Aerial spray is carried out with small planes spraying the herbicides over farming fields.


Misters is spraying herbicide from a truck or tractor. The herbicide is sprayed in very small sizes, in the form of mists and rely on the wind to carry it to weeds. When the wind is not strong enough, the spray may not reach all areas of the field or if the wind is too strong then the herbicide may reach too far and cause over dosing.

Blanket Wiper

Blanket wiper also called weed wiper, is a mechanism attached to a tractor, bike or hand held equipment containing strips. These strips act as a wiping surface to weeds. Blanket wiper is a non selective method to killing weeds. It is commonly used on broad aches to destroy weeds.

When there is a height difference between weeds and crops, the blanket wiper (weed wiper) can be used. The method is effective for controlling weeds such as cape tuplip, Paterson’s curse, Guildford grass, arum lily, fressia and bracken fern.

Rope wick applicators

The rope wick method is a series of ropes are attached to a frame either on a tractor or a hand held device. The rope is saturated with herbicide. The saturated rope makes contact with the weed and in the process the herbicide is applied to the surface of the weed.

Rope wick is not a common used applicator to killing weeds, however it has some success to it. Usually when there are crops and weeds on the same field and there is a height difference between crops and weeds, then the rope wick method can be used.

Weed Detection Technology

Detection technology application uses a tractor fitted with infrared and herbicide to control weeds. The infrared detects the weed and sends a signal for the herbicide to spray on the target weed.

Using detection technology to kill weeds reduces wastage, targets weeds effectively and can be used on large areas.

Other methods for applying herbicide

For private home owners who have a much smaller area to remove weeds, then it is best to use single nozzle herbicide made in small quantities or manually pull out the weeds.

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