Objective The study was carried out to evaluate the control effect of 5% emamectin benzoate water dispersible granule (WG) against Lepidoptera pests in field.

Method Field plot test and five point sampling method were adopted to investigate and calculate the field control of 5% emamectin benzoate WG against Spodoptera exigua and Cnaphalocrocis medinalis.

Result After spraying for 7 d, the control effects of 5% emamectin benzoate WG (active ingredient, ai) of 7.5 g/hm², 12.0 g/hm² and 15.0 g/hm² against S.exigua were 82.87%, 89.37% and 91.02%, respectively. After spraying for 14 d, the control effects of 5% emamectin benzoate WG (ai) of 7.5 g/hm², 12.0 g/hm² and 15.0 g/hm² against C.medinalis were 90.32%, 94.20% and 98.03%, respectively.Significant difference analysis results indicated that the 7 d and 14 d control effects of the 5% emamectin benzoate WG of 12.0 g/hm² treatment against S.exigua were higher than those of 5.7% emamectin benzoate emulsifiable concentrate (EC) treatment.The 14 d control effect of the 5% emamectin benzoate WG of 12.0 g/hm² treatment against C.medinalis was higher than that of 5.7% emamectin benzoate emulsifiable concentrate (EC).

Conclusion The 5% emamectin benzoate WG showed good field control against S.exigua and C.medinalis.Moreover, it had a long duration, no harm to crops and no adverse effects on beneficial organisms.