4Aphids alter plant development and can transmit viruses, thus representing a 5 major threat for crops. Aphids may be controlled through cultural practices, 6 however classical agronomic and ecological models are not suitable to explore 7 their effects on plant pest interaction. Generally, the former do not explicitly 8 consider the dynamics of pest, the latter have a too simplistic representation 9 of the plant. In the present work, we extended a classical plant growth model, 10 describing carbon and nitrogen assimilation and allocation, by integrating 11 the population dynamics of an aphid population and the development of 12 plant defences. We calibrate the model against data of peach Prunus persica 13 subjected to different fertilization and irrigation regimes, infested by the 14 aphid Myzus persicae. Our results suggest that aphid infestation induces 15 the plant to produce defensive compounds that impair aphid ingestion and 16 fecundity. Our model, parametrized for the peach-green aphid system, shows 17 that all these apparently contrasting empirical evidences can emerge from 18 1 the same biological principles governing plant-pest dynamics and that both 19 plant vigour and plant stress hypotheses can find support when observing a 20 plant-pest system.
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Introduction 22Aphids are specialized herbivores that feed on the phloem of vascular plants. 23 They are responsible for the depletion of the plant's yield, which affects plant 24 growth and reproduction and eventually impacts crop production (Goggin, 25 2007; Zvereva et al., 2010). Moreover, aphids can transmit viruses with 26 detrimental effects on the plant and on the yield (Zust and Agrawal, 2016).
27In agriculture, aphids control mostly relies on the use of chemical pesticides 28 with inherent environmental costs and whose efficacy decays in time due to 29 the emergence of resistant strains (Matson et al., 1997).
30In the last decades, agroecology developed as discipline to provide alter-31 natives to the use of chemicals in agronomy. The rationale is that ecological 32 concepts and principles can be applied to control pest populations while 33 reducing the use of pesticides (Gliessman, 2007). The concept of "bottom-34 up" control, on the basis of which population dynamics are driven by re-35 sources quantity and quality, is particularly interesting in agroecology. In 36 fact, there exist a number of agricultural practices that can affect plant 37 physiology and alter the level of resource offered by plants to pests (Gonthier 38 et al., 2013; Kytö et al., 1996; Awmack and Leather, 2002; Coley and Bryant, 39 1985). For example, fertilization modifies nutrient balance in plants, enhanc-40 ing plant tissue nutritional status, and influences the synthesis of defences 41 42 tion controls plant vigour, phloem nutritional quality and viscosity, possibly 43 regulating aphid abundance (Sevanto, 2014; Girousse et al., 1996). However, 44 the way a pest is affected by the plant status is not obvious and empirical 45 evidences provided support to different hypothe...