Dissemination and impacts of the fungal pathogen, Colletotrichum gloeosporioides f sp miconiae , on the invasive alien tree, Miconia calvescens , in Tahiti (South Pacific)

• Published in: Proceedings of the XII International Symposium on Biological Control of Weeds, La Grande Motte, France, 22-27 April, 2007 pp. 594 - 600
• Main Authors: Meyer, J. Y, Taputuarai, R, Killgore, E
• Format: Book Chapter
• Language: English
• Published: Wallingford, UK CAB International 2008
• Subjects: angiosperms; Ascomycota; biocontrol; biocontrol agents; biological control; biological control agents; biological control organisms; bush currant; death rate; Developing Countries; eudicots; eukaryotes; exotic organisms; exotic species; forests; France overseas; French Polynesia; fungi; fungus; Glomerella; Glomerella cingulata; Glomerellaceae; introduced organisms; introduced species; invasive organisms; invasive species; invasives; Melastomataceae; Miconia; Miconia calvescens; monitoring; mortality; Myrtales; natural enemies; non-indigenous organisms; non-indigenous species; non-native organisms; non-native species; nonindigenous organisms; nonindigenous species; Oceania; Pacific Islands; pathogens; Pezizomycotina; Phyllachoraceae; Phyllachorales; phytopathogenic fungi; phytopathogens; plant pathogenic fungi; plant pathogens; plants; Polynesia; rain forests; Society Islands; Sordariomycetes; Spermatophyta; surveillance systems; velvet tree; weed control; weed trees and shrubs; weeds; woody plants; woody weeds; Tahiti
• ISBN: 1845935063; 9781845935061
• DOI: 10.1079/9781845935061.0594

Long-term monitoring of biological control agents in their areas of introduction is essential to assess their effectiveness. There is a need to monitor and evaluate agent dispersal and impacts so that the degree of success can be quantified or reasons for failure can be clearly understood. A fungal pathogen, f. sp. Killgore & L. Sugiyama (Melanconiales, Coelomycetes, Deuteromycetinae), found in Brazil in 1997 was released in the tropical oceanic island of Tahiti (Society Islands, French Polynesia, South Pacific) to control miconia, DC (Melastomataceae), a small tree native to Tropical America, which has invaded native rainforests. The plant pathogen, proven to be highly specific to miconia, causes leaf spots, defoliation and eventually death of young seedlings in laboratory conditions. Two permanent plots in Tahiti (Taravao Plateau and Lake Vaihiria) were monitored for a period of 6 years to assess the pathogen's dispersal and impacts on miconia in the wild. Leaf spots were observed approximately 30 days after inoculation. Percentage of infected plants reached 100% after 3 months, and between 90% and 99% of leaves were infected. Subsequent re-infection occurred after 3 months at Vaihiria and 18 months at Taravao. Mortality rate for monitored plants was 15% and reached 30% for seedlings less than 50 cm tall. Within 3 years, the fungus had disseminated throughout the island of Tahiti and had infected nearly all the miconia plants up to 1400 m in montane rainforests. It was also found on the neighbouring island of Moorea without any intentional release there. Leaf damage on miconia canopy trees increased from 4% to 34% with elevation in permanent plots set up between 600 and 1020 m. Our study showed that rainfall and temperature were two limiting environmental factors that affected fungal spread and disease development. Although this plant pathogenic agent is successfully established, has spread efficiently and has caused significant impacts on seedlings, additional biocontrol agents are still needed to fully control the massive invasion by miconia in the Society Islands.