The chemical that improve the herbicidal effects or efficiency of herbicides are called adjuvants.

Types of Adjuvant:

1) Wetting Agents: (Surfactants or Surface Active Agents or Spreaders):
They posses surface modifying properties and aid in wetting the waxy leaf surface with the aqueous herbicide sprays. E. g Teepol, Uphar, Soda Solution, S-145, Aliquat-4 and Hydrowet (use in soil applied herbicide for avoiding percolation or leaching losses), Surfactant concentration in spray liquid is 0.5 to 1 %.

2) Stabilizing Agents: (Emulsifiers and Dispersants):

They stabilize the herbicide solution for avoiding constant agitation of herbicide solution during application. Generally the suitable stabilizing agents are pre added in the herbicides by manufactures.

a) Emulsifiers:

 They stabilize or dispense the emulsion concentrate ( EC) into minute droplets throughout the herbicide spray E. g 15-S-3, Tergitol-NPX, ABS, Solvaid , Altox -3406 to 3408.

b) Dispersants:

They stabilize suspensions (Wettable Powders) E. g Multifilm, Biofilm and Tryad.

3) Solvents and Co-Solvents (Coupling Agents) :

They solublize herbicide in a concentrated form in so far as the resulting solution is soluble or miscible with water in all proportions. E. g 2,4-D ( acid form) is insoluble in water but can be dissolved I polyethylene glycol to make it water soluble.
Other Examples: Lanolin, methyl chloride, benezene, HAN, xylene, various alcohols, acetone etc.

4) Humicants: (Hygroscopic Agents):

They prevent rapid drying of the herbicide spray on foliage thus they extent opportunity of their absorption. E .g Glycerol.

5) Stickers or Filming Agents (Deposit Builders):

They are added to the herbicide concentrate to hold the toxicants in intimate contact with the plant surface against washing away. Many herbicide are pre-provided with stickers otherwise these can be added to the herbicide spray. E .g Petroleum oils, Citowett and Cheverson spray sticker.

6) Activatars: (Synergists) :

They co-operate in giving fillip to the phyto-toxicity of the herbicide by improving their absorption and or translocation in target weds. E. g Phytobland oils or crop oils, is paraffinic oils or Urea , ammonium chloride in 2,4,-D.

7) Drift – Control Agents (Thickening Agents):

They reduce the possibilities of spray drift hazards to neighboring sensitive crops by either increasing droplet size or forming foam or making invert emulsion. E. g Sodium alginate. Dagagin.
Drift control agents are necessary in aerial application of herbicides.

8) Compatibility Agents:

Herbicides and compatible (Without effect on properties of either) fertilizers, pesticides etc. can be applied at a time.

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