Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 27, 1996
Publication Date: N/A
Interpretive Summary: Pheromones are volatile chemicals used to monitor the presence and amount of important insect pests in crop fields. The Freeman sap beetle is a pest of corn and can introduce and transmit damaging fungi from ear to ear. The synthetic pheromone used to monitor the Freeman sap beetle contains 8-30% of a closely related substance with unknown effect on pheromone bait activity. In this study, we found that the closely related substance acts as an inhibitor of Freeman sap beetle response to the pheromone bait but only at concentrations at least three times that found in the technicial grade pheromone used in crop fields. Therefore, use of the synthetic material can continue without the need to supply much more expensive higher purity pheromone bait.
Technical Abstract: Males of Carpophilus freemani Dobson (Coleoptera: Nitidulidae) produce an aggregation pheromone that attracts beetles of both sexes. The major component of the pheromone was previously identified as (2E,4E,6E)-5-ethyl-3-methyl-2,4,6-nonatriene. The response of C. freemani to this pheromone in a wind tunnel bioassay was inhibited 26-47% (P<0.01) by a tenfold excess of (2E,4E,6Z)-5-ethyl-3-methyl-2,4,6-nonatriene, a double-bond configurational isomer. This artifact of synthesis is not produced by C. freemani and does not attract C. freemani. In the presence of a "host type" coattractant, significant inhibition was not observed with equivalent amounts of pheromone and pheromone analog. Although technical grade pheromone, used to monitor C. freemani in the field, contains 8-30% of the pheromone analog, this amount of the analog is insufficient to cause significant inhibition.