Paper Reviewed
Boullis, A., Francis, F. and Verheggen, F. 2018. Aphid-hoverfly interactions under elevated CO2 concentrations: oviposition and larval development. Physiological Entomology 43: 245-250.

According to Boullis et al. (2018), it has been hypothesized that rising atmospheric carbon dioxide concentrations will change plant-insect relationships by altering the ability of a predator or parasitoid to "locate their prey or hosts by identifying chemical cues emitted either by the infested host plant or by the insect herbivores that feed upon them."

In a test of this hypothesis, Boullis et al. conducted a series of controlled-environment experiments, the first of which examined the preference of a predatory hoverfly (Episyrphus balteatus) to lay eggs on aphid (Acyrthosiphon pisum) prey-infected broad bean (Vicia faba) plants that were reared under conditions of either 450 ppm (ambient) or 800 ppm (elevated) CO2. A second experiment examined the growth and development of hoverfly larvae fed with aphids from the ambient and elevated CO2 treatments, while a third experiment analyzed differences in volatile organic compounds from plants and pheromone emissions from aphids that were exposed to the two CO2 treatment levels.

The results of the three analyses revealed that (1) on average, 31 percent more hoverfly eggs were laid on the plant-aphid system under ambient CO2 conditions than under elevated CO2 conditions, (2) no difference was found among any of the growth and development parameters of hoverfly larvae fed with aphids reared under either ambient or elevated CO2, and (3) no difference was observed in the total quantity of volatile organic compounds emitted under ambient or elevated CO2 conditions, whereas the emission of one pheromone was lower under elevated CO2.

Given the above findings, Boullis et al. conclude that "under higher CO2 concentration, hoverflies will still be able to locate appropriate oviposition site and to control aphid populations efficiently." And that suggests that there will be no overall CO2-induced change in this predator-herbivore/prey-plant relationship in the years and decades to come.