Abstract:
A putative male-produced pheromone has recently been described for the global pest of
pines, Sirex noctilio, but field-activity has not been demonstrated. This study aimed to investigate
the pheromone biology of S. noctilio in more detail. Specifically, we i) analysed effluvia
and extracts for additional compounds by gas chromatography coupled with electro-antennographic
detection (GC-EAD), mass spectrometry (GC-MS) and two dimensional time of
flight mass spectrometry (GC X GC TOF MS), ii) conducted dose-response experiments for
putative pheromone components, iii) determined the site of synthesis/ storage of the putative
pheromone and iv) determined the release rate of the putative pheromone from males
and three types of lures. A blend of four compounds was identified, including the previously
described (Z)-3-decenol and (Z)-4-decenol, and two new compounds (Z)-3-octenol and (Z)-
3-dodecenol. All compounds elicited a response from both male and female antennae, but
the strength of the response varied according to sex, compound and dose tested. (Z)-3-
Decenol and (Z)-3-octenol at lower and higher doses, respectively, elicited larger responses
in males and females than the other two compounds. (Z)-3-Octenol and (Z)-4-decenol generally
elicited larger female than male antennal responses. The site of synthesis and/or storage
in males was determined to be the hind legs, likely in the leg-tendon gland. The relative
release rate of the major compound by male wasps was shown to be 90 ± 12.4 ng/min,
which is between 4 and 15 times greater than that observed from typical lures used previously.
These observations are consistent with the hypothesis that these compounds may
mediate lek formation in S. noctilio males and lek location in females.
