Surveys on Alligator Weed (Alternanthera philoxeroides) in Argentina and Bolivia: Rust and other Fungal Pathogens as Possible Biological Control Agents

M.G. TRAVERSA; A.J. SOSA; M. KIEHR; R. DELHEY; M.H. JULIEN

Vancouver

Congreso; 5th International Weed Science Congress; 2008

Alligator weed (Alternanthera philoxeroides, Amaranthaceae) is an evergreen species native of South America. It is an invasive plant in Australia, USA, China and other countries. To identify possible candidates for the biological control of this plant, surveys of fungal pathogens were carried out in Argentina (November 2004 to May 2005) and Bolivia (August 2007). In Argentina, many sites were explored and several pathogens have been found in Buenos Aires, in the northwest and northeast provinces. Colletotrichumorbiculare, Colletotrichum cf. capsici and Fusarium sp. have been found associated with stem lesions and leaf spots; Albugo bliti (on A. philoxeroides and A. aquatica), Phoma sp. and Phomopsis sp. have also been identified. Uredo pacensis Lindq. is a rust described in 1957 on A. philoxeroides in the yungas formation near La Paz, Bolivia. We rediscovered and collected this rust at several sites near Coroico, La Paz Province. Cinnamon-coloureduredinia were found on leaves. The very thick apical wall of the urediniospores identifies our collections as similar to the original U. pacensis. A high incidence in and an important impact on the host populations were observed. Our field surveys will concentrate on some places of north-west of Argentina where the environmental conditions are similar to the sub-tropical Bolivian yungas. Finding the rust in Argentina would facilitate further studies on its biology, specificity and impact. Future research should consider surveys for other pathogens in different regions and seasons in Argentina.