Attraction of steamed Japanese larch (Larix leptolepis (Sieb. et Zucc.) Gord.) heartwood to the subterranean termite Coptotermes formosanus Shiraki (Isoptera: Rhinotermitidae)

The attraction of steamed Japanese larch (Larix leptolepis (Sieb. et Zucc.) Gord.) heartwood to the subterranean termite Coptotermes formosanus Shiraki was investigated with choice tests and no-choice tests. Wood samples were prepared from green larch boards steamed at 170 degrees C for 30-240 min. In a choice test and a no-choice test, weight losses due to the termite attack were very small in non-steamed samples while they were large in steamed ones. Steamed samples extracted with hot water were not attacked by termite in a choice test. Japanese cedar (Cryptomeria japonica D. Don.) wood specimens treated with water soluble fractions from the hot water extractives of larch were preferably attacked in a choice test. These phenomena suggest that steaming produces attractants and degrades, removes and/or modifies some larch wood constituents which suppress the termite attack.