Buzzing with benefits: Short-term on-farm grassland set-asides support beneficial insects
Introduction
We studied how on-farm grassland set-asides affect the number and variety of both beneficial predatory insects and plant-eating insects compared to conventionally managed cropped fields. Insects are vital to agriculture as they provide pollination, pest control, and nutrient cycling. However, terrestrial insect populations are declining by up to 10% each year as a result of factors such as habitat loss, pesticide use, and climate change. Farmers can help reverse this trend by creating non-crop habitats, such as short-term grassland restorations, which support beneficial insects that, in turn, can provide benefits to crop production.
Farms in this study participate in the Delta Farmland and Wildlife Trust’s grassland set-aside program, which helps offset the costs of planting and managing short-term grassland set-asides. In the program, grassland set-asides are farm fields that are planted with grasses and broad-leaved plants and are left to grow for up to four years before returning to crop production. These fields mimic the historic grasslands in the area and help restore degraded land, transition fields from conventional to organic production, and/or diversify crop rotation for soil health.
We evaluated two types of grassland set-asides:
- ‘Traditional grassland set-aside’: includes plant species that mimic historic tall grass habitats.
- ‘Flower-enhanced grassland set-aside’: the same plants species as the traditional grassland set-aside but also includes flowering plants which can support beneficial insect populations (such as pollinators and predatory insects).
About this Brief
This brief was prepared by Juliana Cao from the BC Food Web team with the help of Matt Tsuruda and is based on the following scientific journal article:
Tsuruda, M., Clausen, M., Bondar, D., Kremen, C., & Carrillo, J. (2024). Short-term grasslands in agriculture support both natural enemy and phytophagous arthropod populations. Journal of Applied Entomology, 149(1), 100-110. https://doi.org/10.1111/jen.13364
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Key Findings
- Non-crop areas on farms, such as grassland set-asides, provide important habitats for beneficial insects.
- There were more ground beetles (a beneficial insect), and a greater variety of them, in on-farm grassland set-asides compared to cropped fields.
- There were more predatory insects and plant-eating insects, and a greater variety of them, in flower-enhanced, on-farm grassland set-asides compared to cropped fields.
- Having more types and a larger population of predatory and plant-eating insects can benefit farms because they have potential to reduce pest insect populations by eating them (predatory insects) or competing with them for food (plant-eating insects).