AbstractBACKGROUND: Treating soil with insecticides is thought to be an effective method for termite control. Speed of action and repellency of insecticides are important factors for discussing their barrier effects as soil‐treatment termiticides. The chemical barrier effect of microencapsulated fenobucarb against Coptotermes formosanus Shiraki was examined in the laboratory.RESULTS: Fenobucarb had a significantly faster lethal effect when applied to the mouthparts than to the tergites of worker termites. Soil that had been treated with ≥ 50 mg kg−1 of microencapsulated fenobucarb had a barrier effect within a single day, and could stop or retard the penetration of termites for 7 days. Microencapsulated fenobucarb did not act as a repellent, as indicated by a gradual increase in mortality at ≥ 50 mg kg−1 with slight penetration into the treated soil during the 7 day test.CONCLUSION: The results suggest that microencapsulated fenobucarb is a fast‐acting termiticide, with a good barrier effect as a soil treatment, that also acts as a reduced repellent, retarding entry of termites into treated soil. Copyright © 2007 Society of Chemical Industry