The lethal effect of Decanoyloctanoylglycerol on eggs and larvae of Plutella xylostella L. was investigated. Decanoyloctanoylglycerol was found to be highly effective for population control in egg stage treatment. In a cabbage field, the mixing of Decanoyloctanoylglycerol with insecticides was suggested to increase the lethal effect. In the egg stage treatment of Saburina® containing Decanoyloctanoylglycerol: one of the products of Bacillus thuringiensis preparation, the effect was observed on the hatchling, and the mortality was 100% at 48 hours in the third instar larval stage treatment. In a cabbage field, Saburina® had a density suppressing effect compared with other BT, suggesting the possibility of it being used as one of the insecticides in the control program of P. xylostella.