Insects and pathogens frequently exploit the same host plant and can potentially impact each other’s performance. However, studies on plant-pathogen-insect interactions have mainly focused on a fixed temporal setting or on a single interaction partner. In this study, we assessed the impact of time of attacker arrival on the outcome and symmetry of interactions between aphids (Tuberculatus annulatus), powdery mildew (Erysiphe alphitoides) and caterpillars (Phalera bucephala) feeding on pedunculate oak, Quercus robur, and explored how single vs. multiple attackers affect oak performance. We used a multifactorial greenhouse experiment in which oak seedlings were infected with either zero, one, two or three attackers, with the order of attacker arrival differing among treatments. The performances of all involved organisms were monitored throughout the experiment. Overall, attackers had a weak and inconsistent impact on plant performance. Interactions between attackers, when present, were asymmetric. For example, aphids performed worse, but powdery mildew performed better, when co-occurring. Order of arrival strongly affected the outcome of interactions, and early attackers modified the strength and direction of interactions between later arriving attackers. Our study shows that interactions between plant-attackers can be asymmetric, time-dependent and species-specific. This is likely to shape the ecology and evolution of plant-pathogen-insect interactions.  

Data from a multifactorial growth chamber experiment, including data on plant performance (plant height, number of developed leaves, leaf size and number of shoots), mildew performance, aphid performance and caterpillar performance. Processed in R v. 3.5.1.