Host range of Brachycaudus rumexicolens (Patch), an aphid associated with the Polygonaceae
1998
The aphid Brachycaudus rumexicolens is a recent arrival in Australia where the weeds Emex australis, E. spinosa, and Rumex species are its recorded hosts. Host range on 114 species representing 42 plant families was assessed in the laboratory to determine the aphid species' potential as a biological control agent against E. australis. Survival and reproductive success were measured in clip and/or dialysis-tube cages. B. rumexicolens developed most successfully on Emex spp. and Rumex spp. and to a lesser extent on other Polygonaceae. Lupinus albus (white lupin) and Triticum aestivum (wheat) were the only non-Polygonaceae plants on which B. rumexicolens developed to a degree similar to its usual hosts. At a field site in Western Australia, E. australis and Polygonum aviculare were the only Polygonaceae present and the primary host species of B. rumexicolens. At peak abundance, it was found on other pasture and crop species, but at considerably lower numbers than on its Polygonaceae hosts. It was concluded that this was due to local migration and that populations would not be sustained on non-Polygonaceae plants. It was also concluded that the risk of virus transmission would not be increased by the presence of B. rumexicolens on nonhosts. B. rumexicolens is considered sufficiently safe to use in programs aimed at augmenting the impact of biological control agents on the weed E. australis.
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