Patchiness caused by aphid herbivory and ozone events affects aphid's spread

Aphids exploit different patches that offer a favourable habitat during their life cycle. Continuous colonization of new patches is critical for the survival of these insect pests. We developed a mesocosm experimental system to study the effects of stress regimes on the colonization of plants by aphids. In the first experiment, we treated Eruca sativa Mill (arugula) plants with either low ozone (O3) (ambient air with no O3 added), elevated O3 (ambient air with O3 addition) or low O3 + Myzus persicae aphid feeding, with subsequent observation of natural aphid infestation over time. The second experiment consisted of aphid sources and differently treated aphid sinks. The aphid sources were also exposed to either low or high O3 levels. The colonization of the sinks was then monitored over time and distance from source. The infestation rate was increased if the patches had been recently exposed to aphid herbivory. On the contrary, aphids did not colonize patches that experienced a recent O3 episode. The patches of E. sativa plants without prior biotic or abiotic stress were colonized by aphids at the beginning of the experiment, but infestation was poor and most of the plants remained aphid‐free throughout the experiment. Aphids from control patches had a better chance of successfully disseminate on hosts with previous herbivory, and aphid spread from O3‐stressed plants was generally poor. Hence, the colonization risk for a generalist aphid plague will depend on the space–time arrangement between crop patches with different stress levels. Ozone contamination could have a negative effect on the spread infestation of aphids in annual crops, because of habitat fragmentation. Here, we present important information to understand how physiological traits of individuals can be scaled up to predict changes within populations in a scenario of climate change.