All against one: first results of a newly formed foreign exploration consortium for the biological control of perennial pepperweed

摘要

Perennial pepperweed (PPW), Lepidium latifolium L., is a mustard of central Asian origin that is invading natural and cultivated habitats in North America and is difficult to control with conventional means. Biological control of PPW is hampered by the fact that it is relatively uncommon in its native range and that it has more than 30 native North American congeners. In addition, detailed information on phytophagous organisms and diseases associated with PPW in its native range is sparse. In 2005, aforeign exploration consortium was formed, and in 2006, five field trips were conducted: three to Turkey, one to Kazakhstan and one to Romania and Bulgaria. A total of 28 field sites of PPW were sampled. Based on identifications available thus far and combined with data of previous opportunistic surveys, we reared or sampled 67 phytophagous organisms, only seven of which have previously been recorded from PPW. Although plants in Kazakhstan showed more obvious signs of damage than in Turkey, a similar number of phytophagous organisms were collected. Only three species were found in both countries, indicating two distinct herbivore communities. At least six potential biological control agents were found during these first surveys: one root-mining weevil, Melanobaris sp. pr. semistriata Boheman, and an eriophyid mite, Aculops sp., in Turkey; one gall-forming weevil, Ceutorhynchus marginellus Schultze, a shoot-mining flea beetle, Phyllotreta reitteri Heikertinger, and a fungal leafspot pathogen, Septorialepidii Desmazieres, in Kazakhstan; and a shoot-mining chloropid fly, Lasiosina deviata Nartshuk, in both countries. The shoot-mining flea beetle in particular was found to be very damaging, causing the die-back of shoots. For M. sp. pr semistriata andP. reitteri, we have established a colony in quarantine at CABI and have started to investigate their biology.