Carrizo cane might stem illegal crossings along the Rio Grande, but the “natural barrier” is unwelcome in Texas

By Angelle Bergeron

While the United States Department of Homeland Security is racing to complete construction of an imposing, 18-ft-tall fence designed to discourage entry of illegal immigrants, Mother Nature is fostering another barrier – Carrizo cane.

A non-indigenous species with no herbivores to keep it in check, Carrizo cane grows fast, thick and to a height of 3-10 meters along roughly 170 mi of the Rio Grande. The cane drains precious water from agricultural areas, destroys aquatic habitats and, because it is thick and tall enough to hide a pickup truck, provides a potentially life-threatening hazard to border patrol officers performing their duty.

This spring, two separate test projects will be conducted, each exploring different methods that advocates say will staunch the growth of the cane and create a safer environment for homeland security.

"This cane grows right up to the edge of the water," says Chuck Prichard, public affairs specialist with the Customs and Border Protection/ Border Patrol in Laredo. "It puts agents in harm's way."

That's why the CBP/BP in September asked the U.S. Army Corps of Engineers to help them figure out a way to control the growth of the cane, Prichard says.

(Courtesy of Michael Martin)

"The removal plan contemplated the various methods that have been employed to remove Carrizo cane in other areas," says Robert Hardbarger, corps project manager. "The design team evaluated those methods against several criteria to determine the methods most likely to achieve the desired results in Laredo."

The Laredo pilot project test area is located along a 1-mi, 300-ft-wide area of the Rio Grande near the Laredo Community College fence line. The project will employ three methods to remove the cane: aerial herbicide application, cut-stem herbicide application and mechanical.

The corps awarded CKY Inc. of San Pedro, Calif., a $1.1 million contract for removal, scheduled to begin in March. Aerial herbicide application was deemed most effective for large stands that are almost exclusively cane, Hardbarger says. "The contractor will employ a helicopter with spray nozzles to apply herbicide."

In areas where the cane is heavily mixed with plants the corps doesn't want to harm, the contractor will cut the cane with equipment or hand tools, leaving a stump only a few inches tall. Then the contractor will apply herbicide directly to the stumps.

In relatively flat, accessible areas, where the Carrizo cane dominates vegetation, the contractor "will employ various types of heavy equipment, such as shredders and excavators, to physically remove all biomass, above and below ground," Hardbarger says.
The corps has also awarded a $1 million contract to Gulf South Research Corp. of Baton Rouge, La., to re-vegetate the project area with native plant species.

"The pilot project is intended to evaluate the efficiency and effectiveness of various removal and long-term control strategies," Hardbarger says. "Carrizo cane will still persist, but with much reduced population density and smaller individual plant size."

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Meanwhile, the Department of Homeland Security has teamed up with the U.S. Department of Agriculture to develop its own method of controlling Carrizo cane. "The USDA had an interest in it because of its effects on agriculture and waterborne wildlife," says Mark Kaczmarek, DHS program manager on a pilot project to introduce a natural enemy of the cane. "As the cane grows, it displaces native vegetation and erodes riverbanks, adversely effecting waterborne wildlife. We are looking at it for safety and security."

This spring DHS hopes to introduce into certain areas the Tetramesa Arundo, a non-stinging variety of wasp that is so Carrizo cane diet specific that it would rather die than look for an alternate food source, Kaczmarek says. "The wasp bores holes in the cane to lay its eggs, and the larva causes the structural integrity of the stalk itself to be compromised," he says. "The larva will exit from the stalk and also eat leaves on the plants."

Tetramesa Arundo was found to control the growth of the cane in its native habitat, the Iberian Peninsula, where the cane is sparse and not as tall as that growing in the U.S.

"We've been working in quarantine with these plants and wasps to make sure the wasps won't transfer to native vegetation and crops," Kaczmarek says. In January, the DHS and USDA/ARS had received initial approval for release of the wasp and were working to develop a large enough population for a late March/early April release to an unspecified location. "Tests will continue through this year, with DHS monitoring, and then USDA will continue alone," Kaczmarek says. "Hopefully, by next year we will go to a large-scale release of the insect."

The $2 million project also has scientists looking at the Arundo fly, which likes to dine on new shoots of the cane, and the Arundo scale, a nymph that feeds on the roots of the cane. "Instead of going in there and ripping things up with bulldozers or using herbicides, we are using nature's own control mechanism," says John Verrico, a DHS spokesman with the department's Science & Technology Directorate. "We are using nature against nature."