Biological Control of Perennial pepperweed, Lepidium latifolium

ESTHER GERBER; HARRIET L. HINZ; FALTLHAUSER, ANA C.; CORNELIA COLSCA

2014-02-28/2015-02-01

1-30

Biológica

Rec.Nat.Renov.-Conservacion y preservacion

SummaryPerennial pepperweed, Lepidium latifolium, (PPW), is a highly invasive mustard of Eurasian origin. This project to investigate the potential for biological control of PPW was started in 2004 in collaboration with Prof. Mark Schwarzländer (University of Idaho, USA). In 2005, we joined forces with the Biotechnology and Biological Control Agency (BBCA) in Italy.At present we are concentrating on three potential biological control organisms: the gall-forming weevil Ceutorhynchus marginellus, the root-mining weevil Melanobaris sp. near semistriata and the gall-forming eriophyid mite Metaculus lepidifolii.No-choice oviposition and development tests conducted with C. marginellus in quarantine at CABI have so far revealed that 33 other species support adult development. Several of these have already been tested in multiple-choice cage tests in southern Russia, and results in 2014 showed that the native North American Cardamine breweri was attacked. In simultaneously established openfield tests, galls were recorded on C. brewerii, but no larvae were found. Open-field tests further revealed a single dead larva in Lepidium crenatum and living C. marginellus larvae in L. huberi and L. virginicum. Since these results are of concern, and levels of funding will be reduced in 2015, we decided instead to concentrate our efforts on the mite M. lepidifolii. We will however continue population viability tests with L. eastwoodiae and L. virginicum and rearing of C. marginellus in 2015.Due to problems in obtaining a legal framework to work in Turkey, all tests scheduled for 2014 were suspended. Field surveys were carried out in two neighbouring countries, Georgia and Armenia, not yet covered in surveys in previous years. These surveys focused mainly on M. sp. n. pr. semistriata and M. lepidifolii, the two potential agents we previously worked with in Turkey. The presence of M. lepidifolii was confirmed at a site in Georgia. Plant parts with galls similar to the ones caused by M. lepidifolii were also collected from several sites in Armenia, but no mites could be extracted from this material. Root-mining weevil larvae were found in Armenia, but molecular analyses revealed that they belong to other species than M. sp. n. pr. semistriata. In December 2014, a co-operative agreement was signed with Erciyes University in Kayseri, Turkey,and preparations for an open-field test with M. lepidifolii were initiated. In parallel, a field trip is planned to collect mite infested material in Georgia in spring 2015, import it into the quarantine facility at CABI and try out methods for host-specificity tests developed by BBCA