Higher surfaces of a crop in the landscape increase outbreak risks the following growing season

Abstract

The use of fungicides and insecticides by farmers represents a major threat to biodiversity 1 , endangering agriculture itself 2,3 . Landscapes could be designed 4 to take advantage of the dependencies of pests 5,6 , pathogens 7 and their natural enemies 8 on landscape elements. However, the complexity of the interactions makes it difficult to establish general rules. Despite initial enthusiasm 9 , the many studies opposing cultivated and semi-natural habitats have not revealed a homogeneous response of pests 10 and pathogens 11 to semi-natural habitats. In addition, the question of the impact of crop diversity on pests and pathogens remains largely open 12 . Based on about half a million observations over nine years on 30 major field crop pests and pathogens spread over all latitudes of metropolitan France, we show that the outbreak risk increases with the area of the host crop in the landscape the previous growing season. The impact on the risk of the host crop area the ongoing growing season diverges between animal pests and pathogens. We also confirm that woodlands, scrublands, hedgerows and grasslands do not have a consistent effect over the spectrum of pests. The spatial and temporal distribution of the resource, the host crop, generally prevails over the effects of potential alternative habitats. Territorial and temporal coordination generally promoting crop diversity but excluding a crop at risk a given year may prove to be key levers for reducing pesticide use 14 .

Integrated pest and pollinator management – expanding the concept

“…Taking advantage of differences in mobility among organism groups might render co-management opportunities by ensuring resource continuity in time and space at scales suitable for beneficial arthropods but not for species that damage crops ( Figure 3; Thies et al 2005). Another opportunity is to take advantage of differences in host-plant and habitat preferences between pests and pollinators, for instance by substituting host crop cover with alternative nonhost plants to disrupt resource continuity for pests while ensuring that substituted crops provide resources for pollinators and natural enemies (Schellhorn et al 2015;Delaune et al 2019). At the landscape scale, this can be achieved for multiple crops that benefit from generalist pollinators and natural enemies but suffer primarily from specialized pests.…”

“…Crop type and diversity along with landscape configuration affect pest and pollinator management. Reducing the spatiotemporal continuity of a host crop could effectively reduce pest abundance, particularly of host-specialized pests (Figure 3; Root 1973;Delaune et al 2019), whereas increased crop diversity benefits biological pest control by naturally occurring predators (Redlich et al 2018). The effects of crop diversity on pollinators may be more complex and depend on crop identities and management intensity, where mass-flowering crops (but not intensively managed cereals) promote pollinator populations (Figure 3 Table 1. Achieving IPPM co-benefits may therefore require more nuanced selection of crop composition rather than simply increasing crop diversity.…”

Spatio-temporal point processes as meta-models for population dynamics in heterogeneous landscapes

“…Community structure, population dynamics and species interactions within and between trophic levels are not limited within single plot's borders but depend on the spatial context (e.g., patch size, spatial configuration, landscape composition, habitat connectivity; see Delaune et al (2019)) and on ecological processes at different spatial scales (Pickett and Siriwardena, 2011). The key to understanding and predicting community structure and population distribution lies in the explication of the latent mechanisms and causes underlying observed patterns, which may emerge from the collective behaviour at smaller scale units or may be imposed by larger-scale constraints and the related temporal scale (Levin, 1992).…”