Effects of landscape characteristics on crop pests

There are many expectations from society on the reduction of pesticide use by farmers. More than half of the volume of pesticides is used on field crops (wheat, maize, rape, etc.). A landscape design that could limit the abundance of pests is therefore considered by scientists and public policy makers alike. However, landscape elements can have opposite effects on the various field crop pests. We propose an assessment of the 30 most important pests on 6 of the main field crops in France (wheat, rapeseed, maize, barley, sugar beet, potato). To do this, we compare the observations of the plant epidemiological surveillance network from 2009 to 2017 with the national maps of forests, hedges and agricultural areas.

We observe a very clear trend towards an increase in the presence of pests in a given year and in a given territory according to the size of the crop areas likely to have hosted these pests the previous year (known as "host crops"). The area of the host crop in the same year has a more complex effect: in the case of fungal diseases, the risk tends to increase with the abundance of host crops; conversely, for annual cycle insect pests, the risk decreases with the increase of crops in the landscape.  We also found that woodlands, hedgerows and grasslands had opposite effects depending on the pests and pathogens studied. However, overall, landscapes have a greater effect than intra-plot rotations on the pests and diseases studied, given the current state of rotations in France. Nonetheless, the impact of landscapes on the presence of pests remains fairly weak compared to the effects of climate, which remain predominant.

Could the trends we have identified be used to manage the protection of field crops at the landscape level? The creation of agricultural landscapes aimed at countering the development of pest or pathogen populations by favouring semi-natural habitats does not seem possible if we want to respond to all the bioaggressors present in field crops in France. On the other hand, a diversification of cropping landscapes (species and type of protection) and a dynamic management of crops in the landscape according to the multi-annual evolution of pests and diseases could be considered, but would then be conditional on a territorial concertation between the various stakeholders, in particular the farmers. This work is being pursued within the framework of the MoCoRiBA project, funded by the Ecophyto plan (ANR-001368-P00004321), which aims to provide farmers with a local and personalised perception of the risk linked to pests and diseases, according to their practices and their geographical location, thus limiting the use of pesticides when they are not necessary.

Valuation: Reference: Delaune, T., Ouattara M.S. Ballot R., Sausse C., Felix I., Maupas F., Chen M., Morison M., Makowski D., Barbu C.M. (2021). Landscape drivers of pests and pathogens abundance in arable crops. Ecography vol. 44 (10) 1429-1442 https://doi.org/10.1111/ecog.05433 .

This article was featured on the front page ("Editor's choice") of the journal Ecography when it was published in October 2021