Interaction of Visual and Chemical CUES in Promoting Attraction of Agrilus planipennis

Female emerald ash borers, Agrilus planipennis (Coleoptera: Buprestidae), emit a macrocyclic lactone, (Z)-3-dodecen-12-olide, that increases field trap captures on large-panel prism traps when co-emitted with the green leaf volatile (Z)-3-hexenol. We assessed attraction to these compounds by using visual decoy-baited branch traps, which attract males by mimicking a living female resting upon a leaf. Pairs of branch traps, with and without visual decoy beetles, were placed on green ash, Fraxinus pennsylvanica, trees, which were assigned different odor treatments: 1) no odor, 2) (Z)-3-hexenol alone, and 3) (Z)-3-hexenol-plus-lactone. Male captures were positively affected by the presence of decoys and the emission of either (Z)-3-hexenol or (Z)-3-hexenol plus lactone. The decoy-baited traps with the combination of (Z)-3-hexenol plus lactone caught more males than any other treatment. Greater male captures were associated with continuing captures later in the season, suggesting that decoy and odor attractants remain attractive throughout the flight period. Female captures were not affected by the visual decoys, but odors did influence captures, with the (Z)-3-hexenol plus lactone treatment catching the greatest number of females. The rare female trap captures were negatively correlated with the more common male captures on the odorless and (Z)-3-hexenol-baited traps, but were not correlated with male captures when the lactone was added. Thus, in the absence of the lactone, the visual signal of other conspecifics can inhibit female attraction. However, the pheromone attracts both sexes independently of the visual signal on the trap.