Planting and maintaining a border of trees around agricultural fields will help a family of flies that, in turn, is important to crops, according to a recent University of Alberta study.
Treed field borders supplied over 33 times more hoverflies to canola fields than grassy borders, the research shows.
That's good news for showing how to get the most benefit from the insects in supporting the crops, says Rachel Pizante, a PhD student in conservation biology who led the study.
The family of flies, which resemble bees and wasps, move between the fields and their borders, feeding on nectar and pollen from blooming crops such as canola. In the process, they pollinate the crops, which can boost yield. But the insects also provide a double benefit — their larvae often feed on soft-bodied crop pests like aphids and thrips.
The study provides more knowledge about how to make the most of the services the insect can provide to crops, says Pizante, of the Faculty of Agricultural, Life & Environmental Sciences.
"From an agricultural perspective, the findings mean we can get more bang for our buck," she says. "Planting more treed field borders will keep the adults as pollinators in the crops, and they'll then produce larvae, which leads to more pest control."
Pollinators and pest controllers
It's important to learn more about hoverflies, which tend to be overshadowed by more commonly known pollinators such as bees, Pizante adds.
"Bees can pollinate but they don't have a role in pest control. And other insects, such as some beetles, have larvae that can control pests, but many of them don't pollinate crops. Hoverflies are a major group of common insects that can provide both services."
Using 10 canola fields located in central Alberta, each with at least one treed and one grass border, Pizante measured the insects' back-and-forth movement between the fields and their borders.
The borders with trees and shrubs supplied, on average, almost 85,000 hoverflies per kilometre per week to canola fields, but grassy borders supplied only about 2,500 of the insects, the study showed.
"This means treed borders should be good for crop pollination, because they seem to both produce more hoverflies and keep them in the field," Pizante notes.
