Mass-emergence devices: a biocontrol technique for conservation and augmentation of parasitoids

  • Published source details Kehrli P., Lehmann M. & Bacher S. (2005) Mass-emergence devices: a biocontrol technique for conservation and augmentation of parasitoids. Biological Control, 32, 191-199.


This study is summarised as evidence for the following.

Action Category

Use mass-emergence devices to increase natural enemy populations

Action Link
Natural Pest Control
  1. Use mass-emergence devices to increase natural enemy populations

    A randomised, replicated, controlled study in 2003 at two urban sites in Bern, Switzerland (Kehrli et al. 2005) found higher parasitism of horse chestnut leafminers Cameraria ohridella in trees with mass-emergence devices (averaging 5-16% leafminers parasitised) than control trees without devices (3-10%) at one site and for a March (rather than May) application date. There was no effect of mass-emergence devices (or timing of application) at the second site (4-14% leafminers parasitised in treated trees vs. 5-15% in controls). Leaf loss caused by leafminers was similar in mass-emergence (3-54% defoliation) and control (3-63%) trees at both sites. Devices were placed in horse chestnut Aesculus hippocastanum trees to control leafminer damage using parasitoid wasps (Hymenoptera). Devices were 200 l plastic tubs with four openings covered in a tissue filter with 600 µm mesh size – allowing wasps (but not leafminers) to develop, emerge and disperse into the trees. Horse chestnut leaf litter containing leafminers and parasitoids was placed inside the tubs (10 kg/device). Ten blocks of horse chestnut trees were selected (five at each site) and devices were hung in three trees/block. Two trees had devices (1 device/tree, applied 20 March and 23 May, respectively) and a control tree had no device.

Output references
What Works 2021 cover

What Works in Conservation

What Works in Conservation provides expert assessments of the effectiveness of actions, based on summarised evidence, in synopses. Subjects covered so far include amphibians, birds, mammals, forests, peatland and control of freshwater invasive species. More are in progress.

More about What Works in Conservation

Download free PDF or purchase
The Conservation Evidence Journal

The Conservation Evidence Journal

An online, free to publish in, open-access journal publishing results from research and projects that test the effectiveness of conservation actions.

Read the latest volume: Volume 21

Go to the CE Journal

Discover more on our blog

Our blog contains the latest news and updates from the Conservation Evidence team, the Conservation Evidence Journal, and our global partners in evidence-based conservation.

Who uses Conservation Evidence?

Meet some of the evidence champions

Endangered Landscape ProgrammeRed List Champion - Arc Kent Wildlife Trust The Rufford Foundation Save the Frogs - Ghana Mauritian Wildlife Supporting Conservation Leaders
Sustainability Dashboard National Biodiversity Network Frog Life The international journey of Conservation - Oryx Cool Farm Alliance UNEP AWFA Bat Conservation InternationalPeople trust for endangered species Vincet Wildlife Trust