Invasive weeds can ruin crop and grazing lands, choke waterways, and smother forests. In Texas, weeds have drawn the ire of the Department of Homeland Security (DHS). According to a report published in the current journal of Invasive Plant Science and Management, a giant reed is overrunning border roads and providing cover for illegal activities.
Mediterranean native Arundo donax or Carrizo cane looks like bamboo and can grow 32 feet tall. Like many invasive species, it was imported to solve a problem, erosion, yet created worse problems. Along the Rio Grande and other southern rivers, it harms the ecosystem as well as border security, according to the report. It consumes excessive water in the arid region, harming watersheds and squeezing out other, beneficial plants. “Giant reed is a relentless threat to riparian areas and watersheds in affected states of the United States,” according to the report.
DHS wants a plan to fight Carrizo cane.
The first step is to map the infestation, and researchers used aerial photography to map the area of infestation, for the first time. They could measure the way light reflects off the reeds to tell how much of it was growing in a certain area, including in remote and inaccessible rural areas. The reeds reflect light in a unique way.
The information will provide a baseline to track the results of eradication programs. “Mapping Giant Reed (Arundo donax) Infestations along the Texas–Mexico Portion of the Rio Grande with Aerial Photography” found that 558 miles along the river from San Ygnacio to Lajitas were infested. The reed was much heavier on the United States side of the border. Of the reed growth, 62 percent was on the U.S. side and 38 percent on the Mexican side.
Researchers corroborated the photo-based estimates with ground surveys. They think the study achieved 90 to 96 percent accuracy.
The next step will be developing a method to reduce the weed. Mechanical controls are impractical in the rough terrain along the river. Native insects and animals do not want to eat it, because it is toxic and unpalatable. According to a press release, the weed is “a good candidate for biological control methods. The eurytomid wasp has been tested in a small area of release and found to be a specific enemy to the giant reed, and unlikely to harm native plants.”
From Asian carp to zebra mussels, invasive exotic species of plants and animals are a costly problem. According to a report from Cornell University, they cost the country about $34.7 billion each year. “Invasive weeds can take over cattle grazing areas, as leafy spurge has done in the northern plain states or overrun crops, much like cocklebur in corn and soybean crops throughout North America,” said Dr. Alan Tasker, national noxious weed program manager for the USDA, quoted by the Weed Science Society of America. Exotic species infest about 3 million acres every year.
Carrizo cane seems to be the first invasive species identified as a homeland security risk.
