Research progress on the synergistic regularity and application of spray adjuvants on the foliage-applied herbicides

Weeds affect the agricultural production and development seriously. Chemical control with herbicide is the most time-saving, labor-saving and high-efficiency weed control method at present. Among them, foliage-applied herbicides are widely used because they are hardly affected by soil environment and applied according to weeds, which exhibits high flexibility and selectivity. However, herbicides droplets often splash, roll off, and penetrate difficultly as a result of the unique interfacial characteristics of weed leaf during the spraying process, causing overuse of herbicides, herbicide resistance, phytotoxicity and environmental residue, etc. Adding appropriate spray adjuvants is an effective strategy to solve the above problems. Considering that the application of herbicides should be combined with the weeds and spray adjuvants, it is of great significance to understand their respective action modes for guiding weeds control. This review first introduces the mode of action and application of herbicides, then summarizes the morphological and foliar interfacial characteristics of gramineous weeds, broadleaf weeds and cyperaceous weeds and their influences on herbicide selection. Moreover, the synergistic mechanism of commonly used spray adjuvants on folliage-applied herbicides and the influence of adjuvants on dose transfer process are also elucidated in detail. On this basis, the mechanism and application of spray adjuvants on contact herbicides and translocated herbicides for controlling gramineous weeds, broadleaf weeds and cyperaceous weeds are summarized. In addition, the future development of herbicide spray adjuvants is also prospected, aiming to provide references for the development and application of spray adjuvants in the field of herbicides, and finally achieving the goal of "reducing dosage and increasing efficiency".