Galpern: Surveillance networks for beneficial insects: Can natural habitats serve as insect reservoirs and do they contribute to yield?
Date: August 2020
Term: 4 years
Status: Completed
Researcher(s): Paul Galpern, University of Calgary
SaskCanola Investment: $79,200
Total Project Cost: $237,600
Funding Partners: ACPC, MCGA
Project Summary
Key Messages:
The surveillance network identified a total of 157,407 arthropods of 418 species from 317 sampled areas in southern and central Alberta.
Sampling by the surveillance network developed a geographically extensive database on the distribution and abundance of beneficial arthropods found in Canadian prairie croplands.
Non-crop areas such as wetland margins, field margins and pivot corners were shown to be reservoirs that serve as a source as well as a destination for beneficial arthropods at different times of the season.
Wetland margins in particular may be hot spots for beneficial insects that spill over into canola fields.
The research collected evidence that beneficial arthropods found in non-crop areas are available to provide pest control and pollination services to canola growers.
Intensification of cropping systems has altered the prairie landscape, leading to a significant reduction in natural areas. Agricultural producers face conflicting pressure to increase crop production while still maintaining biodiversity in natural areas. Natural habitats and uncultivated areas (“non-crop areas”) within or near fields provides habitat and forage for beneficial insects, which may contribute measurably to canola production by increasing yield through pollination or reducing yield loss through pest predation. Maintaining or improving these habitat patches could be a potential "win-win" for biodiversity and yield.
Canola is a dominant flowering crop on the prairie landscape, yet the relationships between canola productivity, insect biodiversity and landscape features are poorly understood. Canola fields can provide a variety of resources that are beneficial to wild pollinator abundance and species richness. These benefits can be attributed to availability of natural habitat, with significant increase in wild pollinator abundance when canola fields are in close proximity to uncultivated land. While the effects of pollinators on canola have been well documented, the yield benefits of pest control by natural enemies were not previously studied. Specifically, there is lack of understanding on the reciprocal impact of all beneficial insects on canola yield from services provide by wild pollinators and natural enemies of insect pests, and of canola on beneficial insects.
A four-year study was conducted by researchers at the University of Calgary to measure how the proximity to specific natural habitat features is associated with (1) beneficial insect abundance and diversity; and (2) canola yield. Beneficial arthropods including wild bees, spiders, ground beetles, and harvestmen were sampled at 317 sites across central and southern Alberta between 2016 and 2018 (see map on the right), with traps deployed between 500 and 8000 hours at any given site. Trapping locations included field margins and the interior of canola fields and were positioned at multiple distances from field and wetland margins.
The network identified a total of 157,407 arthropods of 418 species including approximately 375 species of wild bees, 42 species of most common spiders and 57 species of ground beetles (in the family Carabidae) in Alberta canola fields. There were also a small number of rare species of spiders and ground beetles that were not identified taxonomically. This sampling has developed a geographically-extensive database on the distribution, abundance and diversity of beneficial arthropods found in Canadian prairie croplands. Furthermore, analyses of the network data showed that non-crop areas such as wetland margins, field margins and pivot corners are likely to serve as a source as well as a destination for beneficial arthropods at different times of the season. Wetland margins, in particular, may be hotspots for beneficial arthropods, and these organisms spill over into canola fields. According to a published study by Vickruck et al. 2019, nearly twice as many wild bees were collected at wetland margins than at traps located at a distance of 75 m into canola fields and demonstrating that the spill-over declines as the distance from the non-crop area increases. Finally, the network collected evidence that beneficial arthropods found in non-crop areas are available to provide pest control and pollination services to canola growers A correlational study of 60 million seeded acres of yield data in Alberta (2012 to 2017) obtained from Agriculture Financial Services Corporation (AFSC) showed that counties in Alberta where fields have more non-crop areas also have slightly higher canola yields (Galpern et al, 2020). This provides preliminary and indirect evidence that non-crop areas can influence canola yield. A pilot study of five fields, that used cages to exclude arthropods from canola plants, also showed that the spill-over of arthropods from non-crop areas may increase canola seed weight (Figure 1). This result is being confirmed with additional field experiments in the second phase of the surveillance network. Different species of beneficial arthropods at study sites have peaks in abundance at different times of the growing season. Therefore, when deciding on timing or even whether to spray for pest insects, growers are advised to think about pollination or pest control services in terms of a portfolio of different species providing services at different stages of crop development.
Figure 1. Three hypothesized effects that together would demonstrate a role for beneficial arthropods in supporting canola yields. (a) A reservoir effect (pink) implies that beneficial arthropods use non-crop features as habitat to support their life cycle, throughout the growing season or at specific times of the year. (b) A spill-over effect (dark green) implies that beneficial arthropods are more abundant within and near to a non-crop feature and that this abundance drops off with distance from the feature; this drop off implies that these features are also hotspots for these animals in the agricultural landscape. (c) A halo effect (light green) implies that any beneficial arthropods spilling over from a feature are providing ecosystem services (e.g. pollination or pest control) to the crop, and this is revealed in a localized difference in crop yields (Figure 2). The “halo” of increased or decreased yield, however, may also be caused by non-living process such as soil moisture or shading.
In conclusion, the surveillance network identified a total of 157,407 arthropods of 418 species from sampled areas and developed a geographically extensive database on the distribution and abundance of beneficial arthropods found in Canadian prairie croplands. Analyses of network data showed that non-crop areas such as wetlands margins, field margins and pivot corners are reservoirs that serve as a source as well as a destination for beneficial arthropods at different times of the season. The network collected evidence that beneficial arthropods found in non-crop areas are available to provide services to canola growers such as pest control and pollination.
Acknowledgement:
This research is part of the Canola Agronomic Research Program. Funding was provided by the Saskatchewan Canola Development Commission (SaskCanola), Alberta Canola Producers Commission (Alberta Canola) and Manitoba Canola Growers Association (MCGA).