Research On Degradation And Sustained-release Behavior Of Spinosad Microspheres

Spinosad microsphere using polylactic acid (PLA) as wall material and Spinosad drug were degraded by sunlight and water. After a certain period of time, change of residual content was determined by HPLC. Protection effect of polylactic acid for Spinosad was investigated under sunlight and water conditions. Results showed that in same time the degradation rate of Spinosad microsphere was lower than the Spinosad drug’s. Half-time of Spinosad was prolonged by using PLA as wall material. Under sunlight condition, regression curve of Spinosad microsphere was y= 0.0094e-0.0642x, R2=0.9749 and its half-time was 11.30 days; regression curve of Spinosad drug was y= 0.0084e-0.0802x, R2= 0.9868 and its half-time was 7.78 days. Under water condition, regression curve of Spinosad microsphere was y= 0.0085e-0.0741x, R2=0.9764 and its half-time was 8.43 days; regression curve of Spinosad drug was y= 0.0074e-0.01061x,R2= 0.9565and its half-time was 4.69 days.This paper determined the slow-release performance of the alexin microspheres by the method of high performance liquid chromatography (HPLC). Different models were used to fit the percentage for cumulative release. Results showed that the release curve of spinosad microsphere using polylactic acid (PLA) as coating material was in accord with first order kinetics equation, In (1-Q)= 0.2633 t+0.8548, R2= 0.9517. Spinosad microsphere polylactic acid microspheres had excellent slow release properties which would help to prolong the control stages.This test studied the control effect of 5% spinosad microsphere suspending formulation on Plutella xylostella (L.) in the field compared with 2.5% spinosad microsphere suspending formulation. Results indicated that control effect of 5% spinosad microsphere suspending formulation on Plutella xylostella (1.) after treating 3 days was relatively poorer than that of 2.5%. And their control effect was69.8%±1.71%,81.5%±1.10%, respectively. The control effects had no significant differences after treating 7 days,82.2%±1.18%,83.1%±1.05%, respectively.The control effects had no significant differences after treating 14 days,74.7%±1.31%, 73.0%±.0 1%,respectively.