## 3 Results and Discussion
### Physical Characteristics of Bifenthrin Diluent with Adjuvants  
Surface tension is the basic physical parameter of spray liquid, which also directly affects the wetting and spreading performance of spray droplets on target crops. In order to explain the differences in wetting phenomena, the surface tension of 3000 times diluent of 10% bifenthrin EC and its mixed solution amended with adjuvants were measured, as shown in Table 2.  
The surface tension of pure water was reduced by about 38% with bifenthrin, and the value tended to decrease as the adjuvant concentration increased. The minimum addition of selected additives can rapidly and significantly decrease the surface tension value. The trend gradually stabilized when the concentration was more than 100 ppm (0.01%). The surface tension of all additive mixtures approached the minimum when the concentration reached 1000 ppm. The critical micelle concentration (CMC) of the mixed solution is the concentration corresponding to the inflection point where the surface tension value rapidly drops and gradually remains stable with the increase in concentration. The surfactant molecules can be enriched on the surface of the solution at an extremely low concentration due to the amphiphilic structure, resulting in an instantaneous drop in the surface tension of the mixed solution. The additive molecules do not aggregate on the surface with increased concentration but associate with each other in the solution to form a micelle suspension, preventing the surface tension of the mixed solution from further decreasing. \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Concentration**} & \multicolumn{4}{c}{**Surface Tension (mN/m) a**} \\ \cline{2-5}  & \multicolumn{4}{c}{**Adjuvants**} \\ \cline{2-5}  & **Silwet L-77** & **6501** & **Greenwet 720** & **JFC** \\ \hline
0 & & 45.436 (\(\pm\)0.473) a & \\
0.01 & 25.106 (\(\pm\)0.025) b & 27.400 (\(\pm\)0.030) b & 34.438 (\(\pm\)0.353) b & 43.897 (\(\pm\)0.499) b \\
0.05 & 21.759 (\(\pm\)0.042) c & 26.939 (\(\pm\)0.032) b & 32.980 (\(\pm\)0.150) c & 40.394 (\(\pm\)0.197) c \\
0.1 & 21.087 (\(\pm\)0.044) d & 26.787 (\(\pm\)0.042) c & 31.759 (\(\pm\)0.063) d & 34.895 (\(\pm\)0.054) d \\
0.2 & 20.727 (\(\pm\)0.058) d & 26.848 (\(\pm\)0.017) c & 30.505 (\(\pm\)0.098) e & 32.805 (\(\pm\)0.070) e \\ \hline F b  & 9631.434 & 5956.842 & 1874.348 & 1169.046 \\ DF & 4 & 4 & 4 & 4 \\ \(p\)-value & \textless{}0.0001 & \textless{}0.0001 & \textless{}0.0001 & \textless{}0.0001 \\ \hline \hline \end{tabular}  
* Means \(\pm\) standard error (\(n=5\)) followed by a different lowercase letter in each column are significantly different at \(p=0.05\) according to [PERSON]’s HSD. b ANOVA model: F-test statistics; DF—degree of freedom.  
\end{table} 
Table 2: Surface tension of bifenthrin diluent mixed with adjuvants in different concentrations. Figure 3: Surfaces of fresh bud (**a**) and young leaf (**b**) with 400\(\times\) magnification observed by 3D laser scanning microscope. Although the surface tension values of the four adjuvants had similar trends, their variation ranges and gradients were quite different. For instance, the pesticide solution amended with a trace amount of trisiloxane Silwet L-77 decreased to the lowest surface tension value with the fastest speed among the four adjuvants with increasing concentration. A small amount of 6501 can rapidly reduce the surface tension of the pesticide mixture to below 27 mN/m. The compound oil Greenwet 720 and the nonionic surfactant JFC had a relatively weaker ability to reduce the liquid surface tension. In general, the effect of the nonionic surfactant molecule on the surface tension of the bifenthrin mixture was greater than with an oil adjuvant. Among the surfactants, the effect was greater in the organosilicon surfactant than in the nonionic surfactant.