Herbicides and Adjuvants

Abstract

Abstract"djuvants are any substance either added in a herbicide formulation or added to the spray tank that modifies herbicidal activity or application characteristics, such as better mixing and handling, increasing droplet coverage, spray retention and droplet drying, increasing herbicide cuticle penetration and cellular accumulation reducing leaching of herbicide through the soil profile, etc. The interactions between herbicide adjuvants and herbicide activity, however, are not simple processes, and depend on factors that include crop/weed leaf surface, droplet characteristics, adjuvant type, chemical form of the herbicide, and environmental conditions. Understanding the complexity of these interactions is essential for optimum herbicide utilization, particularly in prolonging, enhancing and improving the efficacy reduction of the critical rain-free period minimizing herbicide leaching into groundwater and decreasing harmful effects to non-target plants and animals.

Effect of Adjuvants on Herbicidal Activity and Selectivity of Three Phytotoxins Produced by the Fungus, Stagonospora cirsii

“…The adjuvants in formulations of chemical herbicides are used as wetting agents, penetrants, spreaders, co-solvents, stickers, emulsifiers and others. The practical selection of compatible adjuvant is a complicated task because their positive effect is highly dependent on many factors: the nature of the active ingredient, weed and crop features and application techniques [ 22 , 25 , 33 , 34 ]. Our results indicated importance of selection and use of adjuvants in order to increase the leaf penetration and herbicidal activity of natural compounds on the example of three phytotoxic nonenolides.…”

“…The hydrophilic-lipophilic balance (HLB) is commonly used to suggest the applicability of surfactants (e.g., emulsifiers, detergents) as activator adjuvants [ 25 ]. Hasten™, containing non-ionic surfactants and esterified vegetable oil, forms a stable milky dispersion in water which indicates its relatively low HLB value (8–10), whereas other tested adjuvants have HLB number above 16 [ 25 , 36 ]. The oil adjuvants had a higher affinity for the surface waxes of leaves than the surfactants with HLB number 12–20 and ionic surfactants.…”

“…However, such a bioassay obviously does not consider the effect of the adjuvant on many other parameters of the herbicidal formulation, which are important in the practice, such as the droplet formation and plant surface coverage, the drift and evaporation of spraying mixture, etc. [ 25 , 43 , 44 ]. It can partially explain the differences in sensitivity of leaf segments and whole plants to three phytotoxic nonenolides in 0.1% Hasten™.…”

“…The effectiveness of the foliar-applied herbicides on target weeds is highly affected by the type of adjuvant added into formulation [ 20 , 21 ]. On the other hand, the addition of adjuvants can alter the selectivity of chemical herbicides and NPDHs which in turn can lead to the decrease in crop tolerance [ 22 , 23 , 24 , 25 ].…”

Potential effect of wetting agents added to agricultural sprays on the stability of soil aggregates

“…If SAS depends on the presence of hydrophobic bonds between the soil particles (Mao et al, 2019), then the wetting agents have to cause its decrease by the principle of their action on the spray mixture. It follows out from the very essence of all wetting agents, the main goal of which is to increase the wetting ability of spray (capacity of liquid to adhere to 480 the plant surface = decrease is hydrophobicity), which consists of water and active substance of pesticide (Pacanoski, 2015).…”