“Mobilizing plant diversity in apple orchards to improve biological control by diverting ants from rosy apple aphids”
When ants meddle with the fight against aphids
The problem :
Aphids are among the most destructive pests in agriculture: they weaken and transmit viruses to plants. They are the target of most insecticide treatments used by farmers, which are often harmful to biodiversity and health. However, nature has effective allies: ladybugs, hoverflies, and parasitoid wasps feed on these pests. But an unexpected player interfere with this natural regulation: ants.
A natural obstacle: the ant-aphid alliance
Ants and aphids have a mutually beneficial relationship (mutualism). Aphids produce sweet honeydew, which ants love to eat. In exchange, ants protect aphids from their predators. This alliance greatly limits the effectiveness of biological control of aphids by ladybugs and other beneficial insects.
The strategy tested
The Diver'Ant project explores an innovative solution that consists in diverting ants in order to protect apple orchards against ash aphids. The strategy involves planting a variety of plants in the orchard or its borders that can provide alternative sugar sources for the ants. If the ants find their food elsewhere, they will abandon or even prey on the aphids themselves. This would leave the field open for aphid predators and ensure better regulation.
The ongoing experiment
In apple orchards in France and Spain, strips of faba beans have been planted, a plant that has the advantage of producing both a lot of nectar, early flowers in the season and harboring aphids that are not harmful to apple trees. The experiment aims to answer several questions about the impact of field beans on modulating ant feeding and the natural regulation of ash aphids:
- Where are the ant nests located in orchards?
- What resources (honeydew, nectar, insects) do ants collect throughout the seasons?
- How do faba beans influence the feeding behavior of ants?
- What is the impact of field beans on the dynamics of aphid populations and their predators?
The goal
To develop a decision-making tool to guide farmers in managing the vegetation cover in their orchards: where and what to plant to maximize the natural regulation of aphids by reducing the protective intervention of ants.
Funding: French Office for Biodiversity, 2025–2027
