Biological control of downey rose myrtle
Downey rose myrtle, Rhodomyrtus tomentosa (Myrtaceae) is native to Asia but is problematic in Florida and Hawaii, displacing native vegetation. Shrubs grow to 6 feet though plants can be up to 12 feet tall. After being introduced as an ornamental it has spread into native areas, particularly in the understorey of pine forests and sloughs. Infestations occur in central and southern Florida including Lee, Palm Beach, Broward, Dade and Pasco Counties. This plant is fire adapted and significantly resprouts after burning and herbicide application. Rhodomyrtus tomentosa can tolerate some frosts and low salinity. It flowers prolifically in spring, and regeneration occurs through seed drop but not vegetatively. The fruits are edible and seeds are therefore distributed by birds and animals. (Information provided by University of Florida, Center for Aquatic and Invasive Plants, http://plants.ifas.ufl.edu/node/364). In Southeast Asia, particularly Thailand and Hong Kong, downey rose myrtle is very common but not problematic, with many insect herbivores.
Downey rose myrtle in Florida, photos courtesy of ABCL
Beginning in 2001, the Thailand Department of Agriculture and ABCL conducted a one year survey of herbivores in Thailand, aimed at providing base information on which to build a future biological control project. Since then, additional opportunistic observations have been made in the region until 2008 when the U.S. Department of the Interior and more recently the Florida Wildlife and Conservation Commission funded further research. Initially, research has focused on two potential agents, a small moth, Agriothera sp., from Thailand and Hong Kong, whose larvae tunnel in flower buds and fruit and appear to tunnel in tips of stems resulting in their death, and a stem-boring weevil collected in Thailand, Sternuchopsis reticulatus, whose adults feed and larvae tunnel in stems resulting in death of young growing branches. These herbivores would be particularly suitable as biological control agents because they target growing stems, foliage and reproductive parts of the weed.
Agriothera larva, photo courtesy of ABCL
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