Root herbivory by Tipula paludosa larvae increases colonization of Agrostis capillaris by arbuscular mycorrhizal fungi

The objective of this study was to determine if root-feeding by insect larvae affects subsequent colonization of roots by arbuscular mycorrhizal fungi. We investigated grazing by larvae of Tipula paludosa on colonization of Agrostis capillaris by two species of fungi, Glomus mosseae and G. intraradices. Host plants were subjected to 7 days of grazing only, continuous grazing for 42 days, or no herbivory. Those plants with no herbivory had significantly lower levels of colonization by arbuscules and hyphae compared to plants which were grazed for 7 or 42 days. The effect only occurred in the upper parts of the root system, where larvae were active. We suggest that this effect was most likely mediated by a change in quantity and composition of root exudates.