A Biologically Active Analog of the Sex Pheromone of the Emerald Ash Borer, Agrilus planipennis.

The emerald ash borer, Agrilus planipennis (Coleoptera: Buprestidae) (EAB), is an invasive species causing unprecedented levels of mortality to ash trees in its introduced range. The female-produced sex pheromone of EAB has been shown to contain the macrocyclic lactone (3Z)-dodecen-12-olide. This compound and its geometrical isomer, (3E)-dodecen-12-olide, have been demonstrated previously to be EAG active and, in combination with a host-derived green leaf volatile, (3Z)-hexenol, to be attractive to male EAB in green prism traps deployed in the ash tree canopy. In the current study, we show that the saturated analog, dodecan-12-olide, is similarly active, eliciting an antennal response and significant attraction of EAB in both olfactometer and trapping bioassays in green traps with (3Z)-hexenol. Conformational modeling of the three lactones reveals that their energies and shapes are very similar, suggesting they might share a common receptor in EAB antennae. These findings provide new insight into the pheromone ecology of this species, highlighting the apparent plasticity in response of adults to the pheromone and its analog. Both of the unsaturated isomers are costly to synthesize, involving multistep, low-yielding processes. The saturated analog can be made cheaply, in high yield, and on large scale via Mitsunobu esterification of a saturated ω-hydroxy acid or more simply by Baeyer-Villiger oxidation of commercially available cyclododecanone. The analog can thus provide an inexpensive option as a lure for detection surveys as well as for possible mitigation purposes, such as mating disruption.

Effects of larval host plant species on fecundity of the generalist insect herbivore Ennomos subsignarius (Lepidoptera: Geometridae).

The elm spanworm, Ennomos subsignarius Hübner (Lepidoptera: Geometridae), is an eruptive herbivore that feeds on numerous tree species in forests throughout its range. An unprecedented outbreak in an urban environment in St. John's, Newfoundland, Canada, caused severe levels of defoliation to a number of native and exotic hardwood tree species, some of which represent novel hosts for this insect. Increased insect performance on these novels hosts was hypothesized as having contributed to the outbreak. To assess this, percentage larval survival and pupal weight were measured for larvae reared on foliage from six different tree species in a no-choice laboratory bioassay. Adult longevity and fecundity (no. eggs laid per female) were assessed for laboratory-reared individuals, as well as for pupae collected from eight different host tree species from the field. A survey to assess feeding occurrence measured defoliation on eight tree species. During this urban outbreak, sycamore maple, Acer pseudoplatanus, a tree species not native to North America, experienced the highest levels of defoliation. Performance of E. subsignarius (pupal weight, female longevity, and fecundity) on this host was comparable with the known host of elm (Ulmus spp.). Despite the fact that E. subsignaria performed well on several introduced hosts, fecundity levels were much lower than previously published reports, suggesting that the current outbreak is not caused by increased fecundity on these novel hosts in contrast to the hypothesis.