Effects of maize development and phenology on the field infestation dynamics of the European Corn Borer

Plant-pest interactions are governed by phenology, i.e. the timing of stage transitions in interacting species. In response to herbivory, plants have evolved defense mechanisms that vary over the course of their development, meaning pests could face varying levels of plant defenses depending on infestation onset. Here, we investigated how the phenological match/mismatch between pests and plants could impact the success of pests in the field. A two-year field experiment was carried out on a panel of 23 early to late flowering maize inbred lines. Inbreds were sown at three different dates in order to confront European corn borers to different maize developmental stages. Plant development and pest infestation dynamics were monitored over the entire cropping season. Contrasted climatic conditions between the two years of the experiment led to different plant and pest phenologies and allowed us to study the relationship between plant development and the timing of pest attacks. Results showed that pest attack dynamics were affected by plant development and that this relationship was not straightforward. For both years, the significant effect of the interaction between inbred line and sowing date on the success of pest infestation resulted in a complex relationship between infestation success and plant development. The shape and intensity of the relationship depended on the timing of the onset of the pest infestation. When infestation occurred when plants were in a vegetative stage, a non-linear relationship between development and pest incidence was observed with the least and most developed plants being the most infested. When infestation occurred when all plants were in the mature phase, the most developed plants were the least infested. Synthesis: Our results highlight the variability of pest infestation dynamics and underline the effect of plant-pest phenological match/mismatch on pest success. ### Competing Interest Statement The authors have declared no competing interest.