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Title: Evaluation of biogeographical factors in the native range to improve the success of biological control agents in the introduced range

item Goolsby, John
item RACELIS, ALEX - Texas-Pan American University
item GOOLSBY, JULIA - Texas-Pan American University
item KIRK, ALAN - European Biological Control Laboratory (EBCL)
item MASSIMO, CRISTOFARO - Biotechnology And Biological Control Agency
item Grusak, Michael
item Perez De Leon, Adalberto - Beto

Submitted to: Biocontrol Science and Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/3/2013
Publication Date: 9/19/2013
Citation: Goolsby, J., Racelis, A., Goolsby, J.B., Kirk, A., Massimo, C., Grusak, M.A., Perez De Leon, A.A. 2013. Evaluation of biogeographical factors in the native range to improve the success of biological control agents in the introduced range. Biocontrol Science and Technology. 23(10):1213-1230.

Interpretive Summary: Arundo donax, also known as giant reed, or carrizo cane is a large (up to 25 ft tall) perennial grass from Mediterranean Europe, northern Africa, the Middle East, and India that was introduced to North America by Spanish colonists hundreds of years ago for use in roofing and fences. However, giant reed has become a damaging invader in the southern U.S., especially in the Rio Grande Basin of Texas and Mexico, as well as in California. Giant reed forms dense thickets along rivers, canals and reservoirs, removing water that is needed for agriculture in regions where rainfall is scarce, and giant reed also promotes wildfires, displaces native plants and animals, and hinders access and visibility for law enforcement and cattle fever tick eradication personnel along the international border with Mexico. Several insects have been imported from Mediterranean Europe for evaluation and possible release for biological control of giant reed. One of these insects is a tiny 'armored scale,' which attacks the below ground roots of giant reed. Field experiments were done in the native range of the scale to determine which conditions allowed it to flourish and which caused the most damage to the plant. We found that the scale did best in locations that were warm (similar to the Rio Grande Basin) and where the giant reed was the least disturbed by cutting, fires, or other human disturbance. In addition, we predict that the scale would have little or no effect on giant reed grown as a crop due to frequent harvesting and other farm practices that would not favor growth of the scale insect. Lessons learned from these studies have been applied to the research program to help with rearing of the scale and accelerate field impacts where giant reed is invasive.

Technical Abstract: Biogeographical factors associated with Arundo donax in its native range were evaluated in reference to its key herbivore, an armored scale, Rhizaspidiotus donacis. Climate modeling from location data in Spain and France accurately predicted the native range of the scale in the warmer, drier parts of Italy and Greece. Presence of the scale was not associated with soil type or characteristics, but was correlated with a higher percentage of dead stems. Density of the scale on the rhizomes was significantly correlated with increased visibility through the stand of A. donax. Micronutrient sampling using leaf material found that sulfur was negatively correlated with scale density with aluminum and boron positively correlated. Disturbance of field sites by cutting and/or addition of supplemental irrigation during summer appeared to disrupt the synchronized seasonal phenology of A. donax and R. donacis leading to more robust stands. These biogeographical factors from the native range indicate that R. donacis will have the greatest impact in warm, dry climates in the introduced range where A. donax is undisturbed.