Pathogens as potential classical biological control agents for alligator weed, Alternanthera philoxeroides

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

La Grande Motte

Simposio; XII International Symposium on Biological Control of Weeds; 2007

CAB International

Alligator weed (Alternanthera philoxeroides) 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 Buenos Aires and northwestern and northeastern provinces in Argentina between November 2004 and May 2005. Thirty sites were surveyed, and at least 12 fungal species were collected. Colletotrichum orbiculare and Colletotrichum cf. capsici, associated with stem lesions and leaf spots, were widely distributed and showed a high incidence and impact in the plant populations. Fusarium sp., associated with concentric large leaf spots, also had high incidence. The white rust Albugo bliti was collected on A. philoxeroides and on the closely related Alternanthera aquatica, but its impact seems to be limited. Phoma sp., Phomopsis sp. and other fungi have also been identified. The fungi likely to be the most promising as candidates for classical biological control of alligator weed are Colletotrichum orbiculare, Colletotrichum capsici and Fusarium sp.