Effect of polyether organosilicone PSPE adjuvant on wettability of thiamethoxam 25％WG on the surface of cowpea petals
[Aims]This study aims to gain insight into the surface wettability of cowpea petals and enhance the level of precision application of pesticides.[Methods]The contact angles of five distinct petal surfaces(including outer and inner surfaces of banner and wing petals,and outer surface of keel petal)of cowpea flower were measured by sessile drop method,and the free energy of the solid surface was calculated by ZDY method.The static and dynamic contact angles and dynamic surface tensions(DST)of thiamethoxam 25％WG diluents and their solutions with PSPE adjuvant on the surface of petals were measured by sessile drop method and bubble pressure method,respectively.[Results]The results showed that four of the five petal surfaces of cowpea were hydrophobic(the contact angle θ＞90°)and one of them was hydrophilic.The surface free energy of petals ranged from 23.15 to 60.31 mJ/m2.The wettability of treatment solution of thiamethoxam 25％WG on the cowpea petal surfaces was generally poor at the concentrations of 125 and 250 mg/L.After adding the PSPE adjuvant,the contact angle of the pesticide solution on the surface of cowpea petals decreased to less than 20° at 30 s.Additionally,the static contact angle decreased by more than 75％,which was significantly lower than that of the solution without the adjuvant.The contact angle of the pesticide solution with the PSPE adjuvant on the surfaces of five cowpea petals showed a similar downward trend,decreasing rapidly in the first 0-10 s and then steadily decreasing;the DST decreased rapidly within 50-500 ms and dropped to below 23.15 mN/m at 10 s.Increasing the concentration of PSPE adjuvant from 0.05％to 0.1％resulted in a faster decrease in DST.Additionally,the contact angle of the four petal surfaces(including the inner surfaces of banner petals,the outer and inner surfaces of wing petals,and outer surface of keel petal)was less than 10° after 5 s,and the rapid decline time of DST was accelerated.[Conclusions]The addition of a certain amount of polyether organosilicone PSPE adjuvant can help the spray liquid of thiamethoxam 25％WG spread rapidly on the surface of cowpea petals.
cowpea flowercontact anglesurface free energydynamic surface tensionspray adjuvantthiamethoxam WG
万方数据
维普
