Abstract: A study on the effects of insecticides on the populations of tobacco aphid Mysus persicae and its parasitoid Aphidius gifuensis was carried out in 1995.The insecticides carbofuran (3% granule and adicarb (15% granule)were applied in root-zone of tobacco plants during transplanting.The results showed that the population of the aphids were significantly suppressed to lower density in the treatments for 60 days after transplanting.The average densities of the aphids in the treatment were 9.6 (individual/plant, carbofuran)、10.7 (adicarb)and 62~428 (control).The average densities of Aphidius gifuensis in the treatments was not significantly lower than in control.It was suggested that the carbofuran could be applied in root-zone for control the tobacco aphids in tobacco-grown regions in Guangdong province.