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.
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.
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.