Invasive Carrizo cane on a Border Patrol access road near Eagle Pass

Several hundred years ago, a particularly noxious weed from Europe’s Iberian Peninsula hitched a ride to the U.S.-Mexican border, and there it has flourished very well indeed ever since. Variously known as Carrizo cane, elephant grass, giant reed, or—scientifically—Arundo donax L., wherever it is prevalent, this ubiquitous, determined weed chokes waterways, erodes banks and canals, damages bridges, inhibits biodiversity, and affords potentially dangerous illegal aliens the cover they need to slip into the United States across the Rio Grande.

Homeland Security Department officials have called for an immediate operational plan to control Carrizo cane—and no wonder. This weed is very good at what it does. It is dense and seemingly impenetrable, spreading itself quickly with underground rhizomes and shooting upwards of 18 feet. Carrizo cane is a major impediment to Homeland Security Department, Customs and Border Protection, and Border Patrol operations on the international border between Laredo and Del Rio Texas, overrunning border access roads, reducing visibility, and providing dense cover for illegal activities.

“Worst of all, it has no natural enemies in the U.S.,” says Merv Leavitt, Division Director for Border and Maritime Security, DHS Science & Technology Directorate.

But all that is about to change—perhaps with a fly, perhaps with a wasp, perhaps with a scale.

Researchers sponsored by the DHS Science & Technology Directorate have identified natural predators of the Carrizo reed in Europe, and they hope to introduce them here to do battle. Three biological control agents are being considered: Tetramesa romana, known as Arundo wasp, lays its eggs in the cane stem, where the larva cause galls to form in the stem and kill the cane. Larva of Cryptonevra sp., known as Arundo fly, kill new plant shoots. Rhizaspidiotus donacis, known as Arundo scale, feeds on the plant rhizomes.

The biological control program of the Carrizo reed has many components, including quarantine evaluation of agents to make sure our own native ecology is protected, as well as mass rearing and application of agents. The goal is to properly evaluate these agents, select and gain approval for them, and conduct a pilot release program on the Rio Grande near Laredo, Texas. If the pilot test is effective, the U.S. Department of Agriculture will initiate a larger mass-rearing and mass-application program.

“There are some risks,” says Leavitt. “We might find it difficult to rear these agents year-round for study, for instance. Or, range tests might show they are not suitable for release, or the impact might show they are too slow for our operational needs. But biological control of weeds has an excellent safety record both in the U.S. and worldwide, so we remain optimistic.”

For more information on this program, please contact Chris Kelly, Science & Technology Media Liaison, at (202) 447-3477 or via email at christopher.kelly@hq.dhs.gov.

Tetramesa romana Arundo wasp Hymenoptera: Eurytomidae Larva form galls and kill canes	Cryptonevra sp. Arundo fly Diptera: Chloropidae Larva kill new shoots	Rhizaspidiotus donacis Arundo scale Homoptera: Diaspidae Nymphs feed on rhizomes