M. Grossrieder and I. P. Keary

The potential for the biological control of Rumex obtusifolius and Rumex crispus using insects in organic farming, with particular reference to Switzerland. BNI 25 (3)

Abstract:

Rumex obtusifolius and Rumex crispus are pernicious weeds throughout their native and introduced ranges. Infestation of grassland by R. obtusifolius is consistently cited by organic farmers as a particular cause for concern, although both species prove difficult to control even when chemical interventions are allowed. Established plants of both species possess a large and persistent taproot that contains a large reserve of resources. This allows individual plants to tolerate repeated defoliation. The history and growing importance of organic agriculture in Switzerland is outlined. Control methods compatible with organic agriculture are reviewed, including various weeding, mowing and cultivation strategies. The potential for limiting Rumex populations through sward management is discussed in relation to competition studies. Methods for depleting the seed bank and limiting seed production are also discussed. Classical and neo-classical, inundative and augmentative approaches to Rumex biological control are considered. Potential insect control agents, both native and non-native, are evaluated on the basis of studies carried out in Europe and elsewhere, and from the results of an Australian classical biological control programme. It is concluded that the augmentation of native natural enemies is the best approach for Rumex control for organic agriculture in Switzerland, although if the classical approach gains more acceptance in Europe, then non-native agents should also be considered for use in a neo-classical approach.