The efficacy of tree injected with emamectin benzoate (EB) against the Asian long-horned beetle (ALB) was tested in a heavily infested willow forest in Beijing, China. In a 1.7-ha plot, 240 out of 310 trees were treated with two EB formulations at various rates. After fall application, the larval population decreased by 89% in the following spring and by >99% during the second year detected by monitoring new frass emission from marked holes. Consequently, the number of exit holes of emerging adults decreased to 0 in the second year. Re-infestation occurred in the third year after application.This high efficacy and lasting activity might be contributed to: a) a favorable translocation of EB in trees when injected into the sapwood; b) the high intrinsic activity against ALB larvae with LC₅₀ of 20–30 ppb; and c) a reduced lifespan of ALB adults by over 60% when feeding on twigs of EB-treated trees. On untreated control trees, the larval population decreased during the first winter. In the second year after application, the larval population was wiped out during winter and a re-infestation started from border trees by adults flying in from outside the trial plot.This pattern indicates an eradication of the ALB population in the 1.7-ha plot can be expected 2 yr after EB treatment.The benefit of treating with EB on the surrounding population was observed in both the untreated trees and imidacloprid-treated trees, suggesting that treatment of EB benefits both the treated trees and the surrounding trees in the area.