APPLE-POPDYN: an individual-based model linking apple-tree productivity and leaf miner infestation dynamics

Abstract

The extent of crop damage caused by insect pests is economically significant and largely determined by the host selection behavior of individual pest species. According to the plant vigor hypothesis, herbivorous insects prefer vital over stressed plant parts. However, the feedbacks between insect behavior, plant performance, and insect population dynamics remain poorly understood. We developed the individual-based model APPLE-POPDYN to explore how different insect oviposition strategies affect apple tree productivity and insect phenology—feedbacks that are challenging to disentangle with experimental studies alone. The model is based on the interaction between the spotted tentiform leaf miner (Phyllonorycter blancardella) and its host, the apple (Malus domestica). It allows for controlled modification of behavioral traits, thereby enabling a systematic investigation of these interactions. The model includes the generation of meteorological pseudo data, apple tree growth, leaf-level oviposition behavior, and insect population dynamics. APPLE-POPDYN distinguishes between “picky” insects that prefer vigorous leaves and “tolerant” insects that do not discriminate. Picky insects develop faster but spend more time searching for suitable leaves. As a result, they produce more generations per year but achieve lower population sizes and cause less overall damage than tolerant insects. Additionally, increasing infestation levels reduce leaf vigor, negatively feeding back on host attractiveness. Our findings suggest that adaptive insect behavior does not necessarily lead to higher population sizes and provide new insights into the ecological dynamics of plant–insect interactions.