Submitted to: Journal of Chemical Ecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/11/1995
Publication Date: N/A
Interpretive Summary: Sap beetles (family Nitidulidae) are abundant pests in the corn fields of the southeastern United States. The feeding damage they cause to field corn can be tolerated economically, but the beetles can also transmit a fungus to corn: Aspergillus flavus, which produces a deadly chemical called aflatoxin. This latter problem is more subtle but is potentially far more important as a food safety issue. Male sap beetles produce aggregation pheromones (natural chemicals that the beetles emit to attract others of their species to a feeding/breeding site). Synthetic versions of these chemicals can be used to monitor the activity of these beetles in the field and can eventually be a key component in a system to prevent the buildup of aflatoxin. The pheromone of the corn sap beetle, Carpophilus dimidiatus, was identified and synthesized in this research, and now pheromones are known for all of the abundant, southeastern sap beetle species. Finally, a year-long survey with six types of sap beetle pheromones documented the seasonal flight patterns and abundance of the sap beetle fauna in South Carolina corn fields.
Technical Abstract: The major component of the male-produced aggregation pheromone of Carpophilus dimidiatus (F.) is (3E,5E,7E,9E)-6,8-diethyl-4-methyl- 3,5,7,9-dodecatetraene. It attracts beetles of both sexes in the field and is synergized by odors from fermenting bread dough. In the laboratory, individual males produced 0.58 ug +/- 0.35 ug (SD) of the tetraene per day, but males in groups of 10 to 50 produced <2% as much per beetle. A second male-specific compound, (3E,5E,7E,9E)-5,7-diethyl-9-methyl-3,5,7,9-tridecatetraene, was also identified from C. dimidiatus and is about 5% as abundant as the major pheromone component. Carpophilus flight activity was monitored for one year in South Carolina corn fields with the pheromones for C. dimidiatus, C. freemani Dobson, C. mutilatus Erichson, C. hemipterus (L.), C. lugubris Murray, and C. obsoletus Erichson, all in combination with bread dough. The first four of these species accounted for 18, 70, 5.7, and 0.03%, respectively, of the total Carpophilus trapped, but no C. lugubris or C. obsoletus were captured. Captures of C. freemani were as high as 11,400 per trap per week. Species specificity for the first four pheromones was high. Three additional species, C. antiquus, C. marginellus, and C. humeralis, accounted for the remaining 6.3% of total capture. There were two major periods of Carpophilus flight activity: February through June and September through November.