Sub soil and above soil processes

To get insight in the effects of soil disturbance on the control of herbivore thrips by predacious mites. We focus on the moment of weeding and tarring and the effect on predation of onion thrips on leek.


  • Short overview of the literature found (and communication to the SPADE project)
  • Report on the effect of the predatory mite Macrocheles in the presence and absence of straw mulch.
  • A method for quantification of the relation between predacious mites and herbivore onion thrips in a field experiment at Nergena 2010.
  • Data of  a field experiment of the effects of Microcheles species on onion thrips on leek.
  • Article for Biological control.

Timeline approach

Interactions between sub soil and above soil processes on predation of thrips

To reduce the input of chemicals for pest control an increase of the natural pest suppression qualities of the soil is necessary. At a higher resistance of the soil, the presence of pests organism will cause none or little damage to the crop. Soil tillage for and during the cultivation, soil type, addition of organic manure and other organic additives may have an impact on soil resistance. The soil organism can suppress soil born  pests in many ways: for example by means of predation. It is therefore the best to have as much as possible of such favorable organisms in the soil. An important question is how soil communities change as a result of changing cultivation techniques and what the impact will be on above soil pest organism. This project aims to result in recommendations for farmers with regard to reduction of soil tillage activities and best period in which these activities can be done and the effect of the predatory mite Macrocheles sp.

From the combined results of the microcosm experiments, we found that the presence of 30 predatory mites in the soil resulted in a corrected onion thrips mortality of 25%. When the predator density was doubled, the mortality increased significantly by 53%, reaching almost 40%. In the final microcosm experiment (the introduction of second instar larvae instead of first instar larvae of onion thrips) corrected onion thrips mortality reached almost 80% when 60 predatory mites of Melanomys Robustulus were released.

This year the results of one additional microcosm experiment will be worked out in which the effect of the predatory mite in the presence and absence of strawmulch has been measured in a microcosm set up.

And a field experiment wil be performed at Nergena in which the effects of the predatory mite Macrocheles robustulus on onion trips  will be tested.