Overview

          Arundo donax (giant reed) is a member of the grass family (Poaceae) and is native to tropical and sub-tropical regions of Asia and Europe where it grows in freshwater habitats. Arundo was introduced into may regions of the new world as an economic crop plant for the production of wind intruments and thatching for roofs, and for erosion control. However, it has become highly invasive in riparian systems of the southwestern United States and into Mexico. The dynamic flooding nature of rivers in the southwest facilitates the dispersal and rapid invasion of Arundo in these systems. Currently, Arundo is one of the top 5 invasive species degrading natural ecosystems in California (Cal-IPC 2004) and was recently declared a Noxious Weed by the California Department of Food and Agriculture.

      
Bridge damaged by Arundo debris (left). Arundo recovery after an Arundo fueled fire (right).

Arundo has many purported environmental and socio-economic impacts, including:

1) displacing native riparian plants and reducing wildlife habitat quality for protected species
2) reducing water availability by transpiring large quantities of water
3) choking watercourses, exacerbating flooding and promoting channel erosion
4) providing fuel for wildfires, especially near urban areas
5) contributing massive debris to riverbanks and beach areas
6) interfering with recreational use of river corridors by the public

          
Arundo litter accumulation along the California (Ventura Co.) coastline (left). Arundo debris accumulating on the bethos in the Santa Barbara Channel near Santa Cruz Island (right).

Research Objectives

1) Document the impacts of Arundo invasion on riparian ecosystem biodiversity, nutrient cycles, hydrology, and fire cycles.
2) Evaluate restoration potential and strategies in a whole ecosystem context (as many invasive species are present in these systems).
3) Evaluate host-specific biological control agents.


Insects and insect damage

Tetramesa romana
          We recently found an herbivorous wasp (Tetramesa romana Walker) feeding in Arundo stems in Santa Barbara and Ventura Counties. This wasp is the same species being evaluated by the USDA, but has been unintentionally introduced into southern California. We are currently evaluating T. romana distribution and population densities in Arundo stands in California, determining how long the wasps have been here, and potential loss in biomass caused by larval feeding.


Female T. romana ovipositing into new Arundo shoots.

Exit holes caused by emerging wasps.

Herbivorous stem-feeding wasp collected from Arundo stems in the Santa Clara River (CA). Adult wasp (left). Wasp pupae (center). Arundo stems kill by larval feeding (Santa Clara River) (left).

Wasp damage: Gallaries formed by larvae feeding inside stem walls (left). Multiple exit holes from newly eclosed adults (center). Exit hole and damage from wasp feeding (right).

Melanaphis donacis

        
Aphids infesting leaves and growing tip of Arundo.


Collaborators

Alan Kirk, USDA-EBCL, Montpellier, France
John Goolsby, USDA, Weslaco, TX
Gretchen Coffman, UCLA
Dave Kazmer, USDA, Sidney, MT

© 2007 Tom Dudley