This blog post is also available in Swedish here.
Fabian Boetzl talks us through his and his colleagues’ new research on landscape-based strategies to reduce insect pest pressure and crop damage.
The problem
Systemic neonicotinoid insecticides are detrimental to a wide range of beneficial biodiversity, with wild bees as the most prominent example. Due to these observed negative side-effects, systemic neonicotinoid insecticides have been banned in the European Union.
This, however, left some crops without crucial protection against early season pests that had been provided by neonicotinoid seed coatings. In Sweden, spring oilseed rape became vulnerable to early season flea beetle pests. Our aim was to identify new landscape-based strategies for effective pest regulation.
The data
For this study, we used data on flea beetle pest communities and associated crop damage collected in south-central Sweden across five years from 2014 to 2018. The data was collected with a standardised methodology in different projects at the Swedish University of Agricultural Sciences.
To identify landscape-based strategies, we characterised the landscapes at different spatial scales around each field in the dataset. We used digitised land cover maps to measure the cover of different non-crop habitats, the distances to the host crop spring oilseed rape in the previous year and to the potential alternative host crop winter oilseed rape in the same year as well as crop diversity in the previous year and edge-density in the landscapes.
Findings: Spatiotemporal isolation is a promising solution
We found effects of several landscape aspects on different spatial scales, but, these effects were predominantly specific to certain flea beetle pest species and did generally not affect crop damage caused by flea beetles. We found that the cover of forests and pastures as well as crop diversity in the previous year increased the densities of certain flea beetle species while edge-density in the surrounding landscapes decreased the density of other species.
However, increasing spatial isolation from spring oilseed rape fields in the previous year more consistently reduced the densities of most pest flea beetle species and the crop damage caused by these and is thus promising for pest regulation.
Recommendations
Our results show that landscape structure can be used, and landscapes can be planned, for pest regulation. While there is no one-fits-all solution (as many effects are dependent on the ecology of different pest species), we show that isolating host crop fields across years, thus hampering colonisation of the fields by pests, can be exploited to disrupt pest populations across years and reduce crop damage.
Sustainable pest regulation via landscape planning for the reduction of insecticide inputs, however, requires additional in-depth knowledge about the ecology and life-cycles of different pest species and an extensive coordination between scientists, landowners and policymakers.
Read the full article “Spatiotemporal isolation of oilseed rape fields reduces insect pest pressure and crop damage” in Journal of Applied Ecology
