Page 43 - Green knowledge 2025

Photo: Hannu Aaltonen
Cabbage root flies threaten Arctic agriculture
The unique conditions in Northern Norway make it possible to grow swede and turnip on a
large scale despite a short season and low temperatures. Pests such as cabbage root fly,
turnip fly and diamondback moth, however, create challenges for production.
The unique conditions in Northern Norway, with the
midnight sun and low temperatures, allow the culti-
vation of swede and turnip rich in sweetness and
crispness. A warming climate gives longer growing
seasons but also increases pressure from pests such
as turnip fly, cabbage root fly and diamondback
moth.
Cabbage root flies and turnip flies overwinter in the
soil, and populations build up with repeated swede
and turnip cultivation. The diamondback moth
arrives to Northern Norway via air currents. It is
appearing increasingly earlier and is becoming a
growing problem in Northern Norway.
Fleece covers, used to promote early growth and root
establishment of swede and turnip, also protect
crops from pests by forming a physical barrier that
prevents turnip and cabbage root fly egglaying.
“Based on swede growth models, the covers should
preferably be removed when root swelling begins, as
cooler temperatures give better root quality,”
explains Dr Anne Muola. However, if the egglaying
by turnip and cabbage root flies continues, the
removal of covers can result in considerable damage
on marketable yield.
In addition, if the diamondback moth arrives early
and gets under the cover, it benefits from warmer
temperature, and the population can grow fast.
Chemical control of diamondback moth is challeng-
ing under the covers.
Thus, effective pest control requires a holistic
approach, including crop rotation, plant growth
models, pest monitoring, weather forecasts, and pro-
viding habitats for the pests’ natural enemies. In
Northern Norway, developing warning systems and
monitoring relevant pests is a priority.
Purpose: Integrated control methods for diamondback moth, cabbage root fly in Arctic agriculture.
Funding: Arctic Agriculture (KU funds)
Contact: Research Scientist Anne Muola, Division of Biotechnology and Plant Health.
Email: anne.muola@nibio.no | Phone: +47 413 74 516
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