Abstract: Z5, E7-Dodecadien-ol, its acetate and propionate, the major sexpheromone components of the pine caterpillar moth, Dendrolimus punctatus Walker,were isomerized facilely on natural rubber dispensers. The high percentage of the Z,E-isomers in the original synthetic samples decreased quickly. After 15 days the E,E-isomers became dominant. The contents of E, Z-and Z, Z-isomers also increased to certain extent. It seemed that the natural rubber was not a good matrix as a dispenser for sex pheromone with conjugated double bonds. It was also demonstrated that a kind of silicone rubber had minimum effect on isomerization.

Key words: Dendrolimus punctatus Walker, sex pheromone, isomerization, conjugated dienes, Z5, E7-dodecadien-ol, Z5, E7-dodecadienyl acetate, Z5, E7-dodecadienyl propionate