Submitted to: Journal of Chemical Ecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/17/2000
Publication Date: N/A
Interpretive Summary: Research was conducted to identify the aggregation pheromone of the sap beetle Colopterus truncatus (pheromones are blends of natural chemicals that insects emit to attract others of their own species). Sap beetles are pests of figs, dates, corn, and other crops in the United States and elsewhere, and new methods of controlling these insects using pheromones have shown great potential. Insects can "smell" airborne pheromone by using their antennae to detect their species-specific blend of natural chemicals. In this research, we were able to record, using microelectrodes inserted into antennae, the antennal responses when pheromone components where blown over the antenna. This new technique for sap beetles allowed us to pin point and identify those chemicals that are emitted by the insects to attract others of the same species. A synthetic version of the pheromone was tested in a natural environment, and the field data demonstrated that Colopterus truncatus beetles were attracted to this newly identified pheromone. This research has defined the chemicals that will attract a significant agricultural pest, and this information will be of general interest to pheromone scientists and other entomologists.
Technical Abstract: A male-produced aggregation pheromone was demonstrated in Colopterus truncatus Randall (Coleoptera: Nitidulidae) by gas chromatographic comparisons of male and female volatile emissions. Male-specific compounds were identified using coupled gas chromatographic-mass spectrometric (GC-MS) analysis and GC and MS comparison of authentic standards. Physiological activity was evaluated using coupled gas chromatographic-electro- antennographic (GC-EAG) recordings, and electroantennographic (EAG) assays of standards. The male-produced volatiles eliciting responses from male and female antennae (and relative abundance) were (2E,4E,6E)-3,5-dimethyl-2,4,6-octatriene (1) (1.8), (2E,4E,6E)-4,6-dimethyl-2,4,6-nonatriene (2) (100), and (2E,4E,6E,8E)-3,5,7-trimethyl-2,4,6,8-decatetraene (3) (3.3). A fourth male-specific compound, (2E,4E,6E,8E)-4,6,8-trimethyl- 2,4,6,8-undecatetraene (4) (0.6) was not EAG-active. EAG dose- response studies showed that the antennae were most sensitive to 2 followed by 3 and 1. Synthetic 2, binary blends of 1 and 3,and tertiary blends of 1, 2 and 3, were highly attractive in the field when synergized with fermenting whole-wheat bread dough. In the field, cross-attraction to the C. truncatus pheromone components was observed for Carpophilus lugubris Murray, C. antiquus Melsheimer, and C. brachypterus Say.