Do interactions between plant roots and the rhizosphere affect parasitoid behaviour?

This paper reports on the interactions between roots, rhizosphere and parasitoids by testing whether mycorrhizal colonization enhances the attractiveness of arbuscular mycorrhizal and non-mycorrhizal tomato plants towards the parasitoid Aphidius ervi in a wind tunnel bioassay. Some 200 female parasitoids were released individually in the glass chamber of the wind tunnel, 30 cm downwind from the tomato plant. The attractiveness of each target plant was calculated by the percentage of parasitoids that flew directly upwind and landed on it. No plant was infested with aphids to determine the effect of arbuscular mycorrhiza on parasitoid behaviour without the host. Mycorrhizal plants were twice as attractive towards the parasitoid as the control plants, with percentages of attraction approximately 80%, despite the fact that there were no host aphids feeding on these plants. This paper reports on the interactions between below-ground interactions (roots and rhizosphere) and indirect defences (provided by parasitoids). These percentages of parasitoids attracted to the mycorrhizal plants were not significantly different from those recorded in a second experiment against a non-mycorrhizal plant that had been infested by hundreds of potato aphid Macrosiphum euphorbiae for a week. The effect of arbuscular mycorrhizal symbiosis on the development and reproduction of aphid hosts was also tested. Only 16% of the aphids successfully completed their development on arbuscular mycorrhizal plants, and only 8% reproduced, which were significantly lower than those recorded on the control, non-mycorrhizal plants.