Léa Beaumelle and Adrien Rusch introduce their team’s latest research exploring different landscape contexts to identify ways to best foster natural pest control on agricultural lands.
Insects and arthropods play key roles in agricultural systems. Arthropods comprise pests, such as aphids or caterpillars, but also beneficial organisms: predators such as spiders and ground beetles (natural enemies) prey upon insect pests and limit pest populations.
As a result, natural enemies provide a key ecosystem service – natural pest control. And promoting natural enemy communities is key to reaching sustainable food production.
Indeed, relying on natural enemies instead of synthetic pesticides could reduce the environmental footprint of agriculture while maintaining crop productivity. Yet, a key issue is to identify management options able to reach that goal.
Plant diversity is a key aspect shaping arthropod communities. Diverse plant communities offer myriads of resources and habitats where many arthropods thrive and are thus often associated with rich and abundant arthropod communities.
Therefore management options such as diverse cover crops that increase plant diversity in agricultural systems could benefit natural enemy communities and promote natural pest control. But the extent to which such positive effects prevail in different environmental contexts remains unclear.
In this study, we tested if diverse cover crops enhanced natural enemy communities and pest predation rates in vineyards.
We conducted an experiment in 18 vineyards, where we sowed two types of cover crops between vine rows: a diverse cover crop with 20 plant species and a low diverse cover crop with 2 plant species only. We sampled natural enemies (spiders, earwigs, lacewings, harvestmen and ground beetles) and compared their abundance and species richness. We also measured the predation rate of the European grapevine moth, which is an important pest in European vineyards. For that, we placed cards with the same number of moth eggs in the field during three days and assessed the number of eggs remaining at the end.
We found that increasing the diversity of cover crops benefits natural enemies and pest predation rates in vineyards. However, these effects highly depend upon the landscape context.
Our vineyards were located along a landscape gradient ranging from 20 to 60% of semi-natural habitats (forests and grasslands) in a 1 km radius around each vineyard. Our results showed that diverse cover crops benefited natural enemies and natural pest control the most in simple landscapes (those with fewer than 50% of semi-natural habitats). Indeed, semi-natural habitats offer resources and refuges to natural enemies.
When such habitats are rare in the landscape, natural enemies may benefit more from diverse cover crops than when landscapes hold high proportion of semi-natural habitats. We found that diverse cover crops increased predation rates by 11 to 42% in simple landscapes. Such an increase could have important implications for grape production and reduction in insecticide use.
Our study thus indicates that diverse cover crops enhances natural enemies and pest control services, especially in simplified vineyard landscapes. Winegrowers aiming to maximize natural pest control could thus prioritize increasing cover crop diversity in simple rather than complex landscapes. More generally, we conclude that the landscape context is a key driver of the success of agroecological practices to improve biodiversity and natural pest control.
Read the full article: “Benefits of increased cover crop diversity for predators and biological pest control depend on the landscape context” in Issue 2:3 of Ecological Solutions and Evidence.
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