Design of Eco-Friendly Compositions Herbicide/Amphiphilic Adjuvant Based on Optimized Structure–Activity Profile

Abstract

To the effectiveness of commercial herbicide, clopyralid, carbamate-containing surfactants were explored as adjuvants. A systematic study of the phytotoxic effect and wetting ability of these compounds by varying the length of the hydrophobic tail and the alkyl substituent in the carbamate fragment (in the presence and absence of an agrochemical) was carried out. Phytotoxic effect was attested in terms of seed germination energy, seed germination, length of roots and seedlings of a number of monocotyledonous and dicotyledonous plants (sweet corn, meadow fescue, watercress, dandelion medicinal). Among the tested surfactants, N-[2-(butylcarbamoyl)oxy)ethyl]-N,N-dimethylhexadecanammonium bromide [Ur-16 (Bu)] demonstrated the optimal characteristics as a potential adjuvant. This surfactant exhibits a high wetting effect, improved transport of pesticide molecules into the plant, relatively low phytotoxicity, and rapid biodegradation. Vegetation experiments demonstrated that the addition of 0.1 wt % Ur-16 (Bu) to the clopyralid solution leads to an increase in the effectiveness of herbicide action by almost 20%, when treating the crops of a weed plant dandelion medicinal. A high selectivity of the proposed herbicidal composition was revealed, i.e., significant inhibition of the growth of dicotyledonous plants (medicinal dandelion) occurred, with no effect observed on monocotyledons plants (meadow fescue). This result contributes to the optimization of functionality/human toxicity/biodegradability ratio, thereby reducing the negative environmental effect.