The Investigation Of Three Insecticides Against Rice Pest In The Lab And Paddy Field

This paper investigated control efficacy of three insecticides, Regent 5%SC, Ethiprole 10%SC and Buprofezin 25%WP against Nilaparvata lugens St?l (Homoptera: Delphacidae) at different application rates and times and the effect of the insecticides on physiology and biochemistry in rice plants in the lab and at potted rice.Experimental results in the lab showed that control efficacy of the three insecticides varied with application concentrations and spray time, of which regent showed over 65% at 20, 30 and 40 days after foliar spray (20, 30 and 40 DAS), but declined gradually over 40 DAS. Ethiprole showed a high control efficacy for all application time. Control efficacy of buprofezin was not very good, especially over 40DAS. Regent and buprofezin didn't showed control efficacy at 60 DAS, ethiprole however, showed good control efficacy at the same time.On the other hand, the control efficacy of all treatments gradually decreased with increase of time after spray. At 40 DAS, buprofezin didn't showed control efficacy, and even did a negative efficacy. Control efficacy of regent was no significantly different compared to the control at 60 DAS, only ethiprole showed good control efficacy. Field experimental results showed there was significant difference on the control efficacy of different treatments to BPH at different times. From the first day after spray (DAS) to 40 DAS, the control efficacy of all treatments was over 60%, except the treatment of buprofezin. After 40 DAS, the control efficacy of all treatments rapidly declined. The control efficacy of regent decreased with increase of DAS. The control efficacy of ethiprole and buprofezin increased during the first DAS and then decreased. That of buprofezin was less than 55% during experimental period. After 40 DAS, the control efficacy of all treatments dropped rapidly.Biochemical tests showed that the content of oxalic acid in rice plants for all treatments decreased with increase of DAS and showed difference compared to the control before 40 DAS, but the difference gradually decreased after 40 DAS with regent and buprofezin treatments, until 50 DAS there was no significant difference. However, the content of oxalic acid in the plants with ethiprole treatment was still significant lower than control at 60 DAS.The Biochemical tests also showed that the content of reducing sugar in rice plants varied with DAS for all treatments increased during the first DAS and then decreased. Until 40 DAS, At 50 and 60 DAS, reducing sugar contents in plants following all treatments did not show significant differences compared to controlThe activity of glutathione-S-transferase (GSTS) in rice plants for all treatments gradually decreased with increase of DAS. That for Regent showed an increase during the first DAS and then decreased, but that for buprofezin decreased during the first DAS and then increased. That for only Ethiprole kept on increase. Regent residue was also determined. The result of recovery experiment showed that recovery rate of regent was in the rang of 86%~91.6%, the coefficient was 4.72%~5.36%. The testable limit was 5μg·kg.-1...