Mating Behavior and Identification of Male-Produced Pheromone Components in Two Woodwasps, Sirex noctilio and Sirex nitobei, in China

To protect vulnerable trees from native and invasive wood wasps, the mating behavior of these two woodwasp species (S. noctilio and S. nitobei, respectively) and factors influencing this behavior were investigated in cages outdoors. Male-produced pheromones were identified in both woodwasp species. Compared with the native species S. nitobei, the invasive species S. noctilio showed stronger mating ability, including mating frequency, time, and duration. The mating behavior of both species mainly occurred from 9:00 to 17:00 each day, peaking at 11:00 and 12:00. The daily mating behavior of both species was most directly related to light intensity. Both female and male S. noctilio and S. nitobei were capable of mating upon emergence, and most individuals mated at 2 days of age. For both species, a female-to-male ratio of 5:15 was most conducive to mating, and individuals with a larger body size were preferred as mates by males and females. (Z)-3-decenol was present in solid-phase microextraction extracts of both species. Two reported minor reference components, (Z)-4-decen-1-ol and (E, E)-2,4-decadienal, were not identified in either woodwasp species. The peak of male pheromone release occurred from 11:00–12:00 for 2-day-old individuals.