Rhaponticum repens (L.) Hidalgo is a clonal Asteraceae plant native to Asia and highly invasive in North America. We conducted open-field experiments in Iran to assess the impact of the biological control candidate, Aceria acroptiloni Shevchenko & Kovalev (Acari, Eriophyidae), on the target weed. Using three different experimental approaches, we found that mite attack reduced the biomass of R. repens shoots by 40-75 %. Except for the initial year of artificial infestation by A. acroptiloni of R. repens shoots, the number of seed heads was reduced by 60-80 % and the number of seeds by 95-98 %. Morphological investigations of the mite complex attacking R. repens at the experimental field site revealed that A. acroptiloni was by far the dominant mite species. We conclude that the mite A. acroptiloni is a promising biological control candidate inflicting significant impact on the above-ground biomass and reproductive output of the invasive plant R. repens. © 2014 International Organization for Biological Control (IOBC).

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