Green leaf volatiles disrupt and enhance response by the ambrosia beetle, Gnathotrichus retusus (Coleoptera: Scolytidae) to pheromone-baited traps

Abstract

Experiments were conducted to test the null hypothesis that green leaf volatiles, abundant in herbaceous plants and angiosperm trees, have no effect on the response by the conifer-infesting ambrosia beetle, Gnathotrichus retusus (LeConte), to pheromonebaited traps. A blend of four green leaf alcohols, 1-hexanol, (E)-2-hexen-1-ol, (Z)-2-hexen-1-ol, and (Z)-3-hexen-1-ol, each released at ca. 4 mg per 24 h, combined with a blend of two green leaf aldehydes, hexanal and (E)-2-hexenal, each released at ca. 13.0 mg per 24 h, reduced catches of females to levels not significantly different from those in unbaited control traps. Any of the four green leaf alcohols released alone disrupted responses of females, while 1-hexanol and (E)-2-hexen-1-ol strongly reduced catches of males. The two green leaf aldehydes released together, and (E)-2-hexenal released alone, weakly enhanced trap catches. These results lead to rejection of the null hypothesis on the basis of both positive and negative effects. Disruptive green leaf volatiles may have promise as forest product protectants against ambrosia beetles, by disguising hosts as non-hosts.