Simulating seasonal drivers of aphid dynamics to explore agronomic scenarios

Abstract

With the regulation of pesticides in European agricultural landscapes, it is important to understand how pest populations respond to climate and landscape variables in the absence of pesticides at different spatial-temporal scales. While models have described individual biological processes, few have simulated complete life cycles at such scales. We developed a spatially explicit simulation model of the dynamics of the bird cherry-oat aphid (Rhopalosiphum padi) in a pesticide-free simulated landscape using data from an agricultural landscape located in southwest France. Using GLMMs, we ran two statistical methods, one at the crop level, focusing on aphid densities within each crop individually (wheat and its regrowth, corn, and sorghum), and another at the landscape level where aphid densities were not differentiated by crops. For each season, we analyzed how temperature, immigration, and habitat availability impacted on aphid densities. Predictors of aphid densities varied between crops and between seasons, and models for each individual crop resulted in better predictions of aphid densities than landscape-level models. Aphid immigration and temperature were important predictors of aphid densities across models but varied in the directionality of their effects. Moreover, landscape composition was a significant predictor in only four of the nine seasonal crop models. This highlights the complexity of pest-landscape interactions and the necessity of considering fine spatial-temporal scales to identify key factors that influence aphid densities, essential for developing future regulation methods. We used our model to explore the potential effects of two agronomic scenarios on aphid densities: (1) replacement of corn with sorghum, where increases in available sorghum led to the dilution of aphid populations in sorghum in spring and their concentration in summer, and (2) abandonment of pastures for wheat fields, which had no significant effect on aphid densities at the landscape scale. By simulating potential future agronomic practices, we can identify the risks of such changes and inform policy and decision-makers to better anticipate pest dynamics in the absence of pesticides. This approach can be applied to other systems where agronomic and land cover data are available, and to other pest species for which biological processes are described in the literature.

Cereal Aphid Parasitoids in Europe (Hymenoptera: Braconidae: Aphidiinae): Taxonomy, Biodiversity, and Ecology

“…Similarly, wheat aphid, S. graminum populations decreased when the mean winter temperature and total fall precipitation increased [225]. Furthermore, Thierry et al [226] reported that high temperatures during spring and winter caused a reduction of the bird cherry-oat aphid R. padi numbers, whereas high temperatures during fall increased the abundance of R. padi. Increases of wind speed, relative humidity, and precipitation decreased the abundance of cereal aphids caught in suction traps [227].…”

How do temperature and plant resistance shape the colonisation dynamics of wheat plants by Rhopalosiphum padi L. (Hemiptera: Aphididae) and barley yellow dwarf virus (BYDV)?

“…This pattern results from a range of environmental factors. Temperature and host-plant resistance are among the primary regulators of aphid populations (Correa et al 2020; Thierry et al 2021; Wiest et al 2021). In addition, density dependence, host alternation, and the impact of top-down ecological relationships (natural enemies) as well as bottom-up factors (such as nutritional quality) are important for investigation of aphid and natural-enemy dynamics (Matis et These factors are directly linked to the tness of these insects, in uencing biological processes such as reproduction, development, survival, and longevity, which can have cascading effects on aphid movement and colonisation of new plants over time (Descamps and Chopa 2011;Strauss et al 2020).…”

“…The use of analytical tools employing spatial scale is not common in studies aiming to understand the mechanisms that modulate the local colonisation of new plants by aphids (Parry 2013; Ben-Ari et al Thierry et al 2021). The movement of aphids at the local scale can be mediated by rapid population growth and resource depletion, or through the search for nutritionally suitable plants (van Emden and Harrington 2017).…”