Submitted to: International Symposium on Biological Control of Weeds
Publication Type: Abstract Only
Publication Acceptance Date: March 1, 2007
Publication Date: April 22, 2007
Citation: Rayamajhi, M.B., Pratt, P.D., Van, T.K., Center, T.D. 2007. Dynamics of invasive plant monocultures following the establishment of natural enemies: an example from the Melaleuca quinquenervia system in Florida. International Symposium on Biological Control of Weeds. Interpretive Summary: Melaleuca is one of the most invasive plants in Florida. It has colonized and replaced native plants from a large portion of natural areas. Host specific natural enemies such as herbivores and pathogens can damage and kill melaleuca trees without damaging other native plants in the area. Currently, several natural enemies (insects and a pathogen) are established on melaleuca trees of Florida. These insects attack and pathogens cause disease on substantial amount of melaleuca leaves. As a result, melaleuca trees slowly but steadily become weaker and gradually die overtime. The surviving trees on the other hand produce fewer seeds. Less seedling recruitment and more death of melaleuca has gradually opened up canopy and forest-floor space for other plants to come in. As a result, many native plant species have occupied the spaces vacated by dead melaleuca trees. Natural enemies are predicted to continue to damage and kill melaleuca trees and eventually create more space for native plants in melaleuca stands of Florida.
Technical Abstract: Melaleuca quinquenervia (melaleuca), a native tree of Australian origin has become one of the most invasive plants in Florida. Biological control was implemented as a long-term solution to melaleuca control in Florida. Now several natural enemies (insects and a pathogen) of melaleuca are well established in Florida. Their impact on melaleuca populations is being monitored for several years. Insect-fungus integration in field conditions showed significant impact on stump-regrowth control of melaleuca. During the period when natural enemies prevailed, melaleuca stand density and basal area declined at a greater rate across study sites. Myrtaceae (represented by melaleuca) and Cyperaceae (represented by sawgrass, Cladium jamaicense) were the first and second most important families during 1997. Their family importance values were reduced significantly during 2004/2005 with the increase of the importance values of other families in the stand. Overall richness and diversity (compared to 1997) of plant species was higher in 2004/2005. Within stands, plant species richness and diversity indices were relatively higher at interior than at peripheral sections. Melaleuca vacated spaces in the stands were colonized mostly by native plant species. This phenomenon is predicted to intensify as the natural enemies continue to impact melaleuca monocultures in Florida.