An investigation into the chemical ecology of the grain chinch bug, Macchiademus diplopterus

Very little is known about the chemical ecology of the grain chinch bug, Macchiademus diplopterus. The objective of this project was to study the aggregation pheromones of the grain chinch bug to ascertain whether they would be useful in the formulation of pheromone lures and trapping methods for this phytosanitary pest.

The presence and effect of aggregation pheromones in grain chinch bug were investigated in three laboratory experiments and two seasons of field trials.

Laboratory bioassays using a four-arm olfactometer were performed to assess the attractiveness of each gender to separate sexes during aestivation in order to detect the presence of an aggregation pheromone. Headspace samples collected from aggregating adult grain chinch bugs were analysed by gas chromatography-mass spectrometry (GC-MS) to identify volatiles, and laboratory bioassays to test the responses of each gender to the identified volatiles were also tested in the four-arm olfactometer.

Results indicated that an aggregation pheromone is release during aestivation, and that females disseminate the pheromone more efficiently than the males. Eight chemical constituents that form part of the grain chinch bug aggregation pheromone were identified.

The chemical compounds were used to formulate lures using glass vial dispensers and two trap types were tested for their effectiveness in trapping grain chinch bug in the field. In the first season, trap catches did not reflect the level of infestation in the field, and the field trial highlighted the importance of a sheltering site for grain chinch bug. A second season of field trials focused on testing another type of dispenser to improve release of the pheromone in the field and confirm it’s efficacy. Further research is required to optimize the lure and trapping system.