The absolute configuration of the primary component of the maritime pine scale (Matsucoccus feytaudi) pheromone (i.e., (8E, 10E)-3,7,9-trimethyl-8,10-dodecadien-6-one) was determined as 3S,7R by field-trapping experiments using synthetic stereoisomers and according to previous NMR considerations. The 3R,7R isomer showed similar activity to 3S,7R, whereasM. feytaudi males responded very weakly to the two other candidates (3R,7S and 3S,7S). Further studies were conducted to optimize scale trapping for monitoring scale populations. Results of these studies showed that the trapping efficiency was related to pheromone dose, trap area, and wind speed but not to trap height.