Value: Impact of beneficials

Beneficial species operate in a fundamentally different way to other agents that control pest species, and that can make their value hard to quantify and recongize. If your goal is to reduce the frequency with which pest populations hit economic thresholds then management of beneficials is ideal. They reduce the risk of pest outbreaks but don’t eliminate them entirely. Furthermore, beneficials require some prey to be present in the landscape in order to survive (i.e. killing all your pests may not be desirable). There are many ways that scientists and growers or agronomists can tell if beneficials are having an impact on pest risk.

  • Reliability and magnitude of pest mortality across time/space (assessed through cage exclusion studies)  ​
  • Reduction in pest population growth across time (assessed through cage exclusion studies or augmentation of beneficials)  ​
  • Relative time of arrival in field of pest and beneficial species ​
  • Abundance and diversity of beneficial communities, or specific beneficial species, co-occurrence with pests in fields at the same time.
  • In cotton the beneficial to pest ratio has been used​​ as an indicator.

Lizzy Lowe (cesar Australia) from explains the challenges associated with measuring the impact of beneficials for individual growers.

We are interested in determining how we can get beneficials into canola fields and actively eating pests early in the season. So we are focussed on the early arrival of beneficials as a potential indicator of impact on pest populations.

What are we doing in 2024?

This year we are focussed on using cage studies to exclude beneficial species at certain points in time to evaluate what happens to pest risk when they are absent. Results to come soon.

Further reading:

Macfadyen S, Davies AP, Zalucki MP (2015) Assessing the impact of arthropod natural enemies on crop pests at the field scale. Insect Science 22:20–34. https://doi.org/10.1111/1744-7917.12174 ​

Chaplin-Kramer R, O’Rourke M, Schellhorn N, et al (2019) Measuring What Matters: Actionable Information for Conservation Biocontrol in Multifunctional Landscapes. Front Sustain Food Syst 3:60. https://doi.org/10.3389/fsufs.2019.00060​