5-Methylheptadecane: Sex Pheromone of the Broom Twig Miner, Leucoptera Spartifoliella, a Biological Control Agent for the Scotch Broom

The broom twig miner, Leucoptera spartifoliella (Hübner) is a highly specific biological control agent for the Scotch broom, Cytisus scoparius (L.). Cytisus scoparius has become a major invasive weed spreading in North America, South America, Australia and both the South and North Island of New Zealand, causing a major disturbance to the ecology of the area where it has been established. Currently, there is no tool available to monitor the population density, dispersal, and establishment of L. spartifoliella. This work was undertaken to identify the sex pheromone of L. spartifoliella and develop a monitoring tool for this biological control agent. Analysis of the extract of the female sex pheromone gland by gas chromatography/mass spectrometry and chemical ionization identified a single compound in the extract. Using the mass spectral data and synthesis of candidate compounds, this compound was identified as 5-methylheptadecane. In a field trapping trial, testing various doses (0.01, 0.1 and 1 mg) of 5-methylheptadecane and virgin females as a positive control, the highest male catch obtained was in traps baited with the 1 mg dose. When testing two releasing substrates for the pheromone (i.e. a glass vial containing a cotton ball and another containing white septum), the male catch in a trap baited with a glass vial with the cotton ball was significantly higher than in a trap baited with a white septum. The identification of the sex pheromone of L. spartifoliella will help to detect and determine population densities, distribution, and dispersal of L. spartifoliella.