Male‐produced aggregation pheromone of Carpophilus sayi, a nitidulid vector of oak wilt disease, and pheromonal comparison with Carpophilus lugubris

Abstract

Abstract 1 Carpophilus sayi, a nitidulid beetle vector of the oak wilt fungus, Ceratocystis fagacearum, was shown to have a male‐produced aggregation pheromone.2 Six male‐specific chemicals were identified from collections of volatiles. The two major compounds were (2E,4E,6E,8E)‐3,5‐dimethyl‐7‐ethyl‐2,4,6,8‐undecatetraene and (2E,4E,6E,8E)‐3,5,7‐trimethyl‐2,4,6,8‐undecatetraene, in a ratio of 100 : 18. These compounds, in a similar ratio, were previously reported to be the pheromone of Carpophilus lugubris, a closely related species. The four minor C. sayi compounds (less than 4% as abundant as the first) were also alkyl‐branched hydrocarbons and consisted of two additional tetraenes and two trienes.3 The pheromone of C. lugubris was re‐examined to refine the comparison with C. sayi, and C. lugubris was found to have the same additional, minor tetraenes as C. sayi, but not the trienes.4 A synthetic mixture of the two major compounds was behaviourally active for both sexes of C. sayi in oak woodlands in Minnesota. The pheromone was tested in combination with fermenting whole wheat bread dough (a potent synergist of nitidulid pheromones). The combination of the 500‐µg pheromone dose and dough attracted at least 30‐fold more C. sayi than either pheromone or dough by itself. The synergized pheromone has potential as a tool for monitoring insect vector activity in an integrated management program for oak wilt.5 Although C. lugubris was not present at the Minnesota test sites, two other Carpophilus species, Carpophilus brachypterus and Carpophilus corticinus, were clearly cross‐attracted to the synergized pheromone of C. sayi.