Small farms and diverse cropping can enhance natural enemy populations. According to Haan et al. 2019, natural enemy populations are are greater when agricultural landscapes are made up of smaller farm fields. The researchers looked at how landscape structure influenced numbers of beneficial insects.

Beneficial insects, which include predatory and parasitic arthropods, are essential for control of herbivorous insect populations. The value of beneficial insects has been estimated at billions of dollars annually (Losey et al. 2006). Crop monocultures are often detrimental to the longer lived natural enemies while encouraging population growth of fast reproducing insect pests.

This makes sense since many arthropods need resources found in field edges and permacultures. Resources includes food, overwintering spaces, nest sites, and a refuge or safe space from agricultural disturbance. Natural enemies can survive in these protected spaces and then move into crop fields to exploit the herbivore insect pests.  

Aspects of the landscape that may influence insect populations include edge density (grain size), shape complexity and connectivity. It is become obvious that landscape configuration is an important predictor of degree of pest suppression.

Increasing crop diversity helped promote important insect predators and pollinators. Landscapes that had both high crop diversity and semi-natural habitat cover, had an increased diversity of ground beetle species and pollinators (Aguilera et al. 2020). Semi‐natural habitats normally are pastures, small forest patches and ponds/other waterways. 

One very important addition to landscape is flowers. Many predatory insects live much longer when they have access to nectar and pollen (HE et al. 2021). Researchers reported that when looking at all predatory insects, females with access to flowers survive 2.2 times longer, while males live 1.7 times longer, when compared to insects that only have access to water, but no flowers.

HOW CAN YOU USE THIS EMERGING RESEARCH IN YOUR OPERATION OR FARM?
  1. Plant flowering hedgerows and permaculture.
  2. Use spaces that are traditionally hard to farm, such as slopes or edges, to develop semi-natural patches of pasture, orchard or hedges for beneficial insect habitat. 
  3. Add pollinator plots and rows between or within your crops using perennial flowers. This benefits both pollinators and predator insects. 
  4. Break up monocultures by growing a variety of crops. Crop diversity helps beneficial insects.  
  5. Consider adding or increasing perennial crops that will provide a year round habitat for beneficial insects. 
  6. Develop an integrated pest program that enhances natural enemy survival. 

References:

Guillermo Aguilera, Tomas Roslin, Kirsten Miller, Giovanni Tamburini, Klaus Birkhofer, Berta Caballero‐Lopez, Sandra Ann‐Marie Lindström, Erik Öckinger, Maj Rundlöf, Adrien Rusch, Henrik G. Smith, Riccardo Bommarco. Crop diversity benefits carabid and pollinator communities in landscapes with semi‐natural habitats. Journal of Applied Ecology, 2020; DOI: 10.1111/1365-2664.13712

Nathan L. Haan, Yajun Zhang, Douglas A. Landis. Predicting Landscape Configuration Effects on Agricultural Pest Suppression. Trends in Ecology & Evolution, 2019; DOI: 10.1016/j.tree.2019.10.003

John E. Losey, Mace Vaughan, The Economic Value of Ecological Services Provided by Insects, BioScience, Volume 56, Issue 4, April 2006, Pages 311–323, https://doi.org/10.1641/0006-3568(2006)56[311:TEVOES]2.0.CO;2

Xueqing He, Lars Pødenphant Kiær, Per Moestrup Jensen, Lene Sigsgaard. The effect of floral resources on predator longevity and fecundity: A systematic review and meta-analysis. Biological Control, 2021; 153: 104476 DOI: 10.1016/j.biocontrol.2020.104476