Conservation of natural enemies in agricultural ecosystems

Willemien Geertsema (Crop Systems Analysis Wageningen UR)
Mirjam Pulleman (Department of Soil Quality Wageningen UR)
Felix Bianchi (FSE Wageningen UR)


Intensification of farming practices and landscape simplification have led to a deterioration of biocontrol services in agro-ecosystems. Within-field crop diversification and provision of overwintering habitat near crop fields may help in sustaining effective densities of natural enemies and enhancing biocontrol services in crops.

We offer the opportunity to conduct research into the role of within-field diversification and disturbances on the conservation of natural enemies. The work will be conducted in a long-term trial on the experimental farm Broekemahoeve in the Flevopolder. Soil disturbance treatments include conventional tillage (ploughing to 25 cm), non-inversion tillage and minimum-tillage. Within-field diversification treatments include monocropping versus strip cropping of six different crops. At this point it is not clear how these soil and crop diversification treatments influence population dynamics of pests and natural enemies, including the winter survival of natural enemies. Possibly, conventional tillage could reduce hibernation success of parasitoids overwintering on cabbage plants as the cabbage is ploughed under after harvest in autumn, whereas less intensive soil disturbance could potentially result in higher hibernation survival of natural enemies. Furthermore, strip cropping could lead to reduced pest colonization and provide more suitable habitats for natural enemies than monocrops. Got interested? Don’t hesitate to contact us!

Possible thesis subjects

By sampling pest and natural enemy populations on crops grown under different diversification and soil disturbance regimes, the effects of these treatments on population dynamics will be investigated. While we offer opportunities for work conducted in the growing season and winter, below are some examples of questions related to the winter ecology of natural enemies:

  • How does the diversification of cropping systems influence the effectiveness of natural enemies in providing biocontrol services in crops early and late in the growing season?
  • What is the fate of parasitized pests during winter in different soil management treatments?
  • Where and when do natural enemies emerge from hibernation in spring?

Used Skills

Various (soil and vegetation) sampling techniques, identification of organisms groups, design and execution of (greenhouse) experiments, data analysis and writing skills.