Study on the Control Effect of Regant with Bt Premix on Rice Stem Borer

The newly hatched larvae of rice stem borer is senstitive to Regant (b 2,LC 50 is 0.04～0.06 mg/ kg),but not sensti-tive to Bt(b is 1.4～2.0;LC50 is 5～8mg/ kg). The experimental results showthat there are a good formula among the agents concerned and when the proportion of Bt :Regent is 1:1～1:3, the synergistic effect is especially good, and co-toxicity index shows an upward trend with increase of Bt content . By combining with field test and economic benefit, the selected formula is that the proportion of Bt :Regent is1:1. It demonstrates from field trial that:2% regant·Bt control effect is 60.34%, 67.73%, 71.32% respectively after 22 days treating with 60,75,90g/mu, which are higher than Bt 16000IU/mg at 50g/mu. The toxicity test of 2% regant·Bt show that it belongs to low toxic pesti-cides.