Herbicides to be used to attack hydrilla - U.S. Army Corps of Engineers, Comision Internacional de Aguas in Mexico are funding the Rio Grande effort

(Note: But ... but ... but -- what about all the Invasive Species legislation being 'fast-tracked' through Congress? Didn't the person quoted here know about that? " ... recommends releasing a Crete-native beetle to eat the salt cedar.")

May 19, 2003

By Sandra Billingsley

The Monitor

To submit a Letter to the Editor: randyd@valleystar.com

Herbicides should help reduce non-indigenous weeds choking the lower Rio Grande.

Diquat, glyphosate and Komeen will soon be applied to attack hydrilla and water hyacinth in the river, said Dr. Earl Chilton, Texas Parks and Wildlife aquatic habitat enhancement program director.

The U.S. Army Corps of Engineers and Comisi Internacional de Aguas in Mexico are funding the effort.

Both countries have contributed a total of $100,000 to battle the aquatic weeds and increase the river flow.

The herbicides, which are U.S. Environmental Protection Agency approved for use in waterways, remained a sticking point for Comision Internacional de Aguas until last week.

Although hydrilla and water hyacinth can be found in long stretches along the lower Rio Grande, the researchers will tackle the most congested areas first.

About 30 acres of hydrilla at river mile 60 near the Brownsville pump station will be attacked with Komeen and diquat. A mechanical shredder also will be used to clear a route through the matted weed.

Water hyacinth is most congested between river miles 35, near Southmost Ranch, to 75 near the Rancho Viejo floodway. Glyphosate will be used on about 150 acres of water hyacinth in this area.

An official with the Comision Internacional de Aguas representative, said the Mexican government wants to make sure the herbicides are safe and would not adversely affect humans, wildlife or livestock.

"We're insistent that the herbicides are very safe," the official said. "I want to insist that more parity is given to mechanical removal in front of the cities. The less chemical, the better."

Researchers this month released 4,000 Asian grass carp into the lower Rio Grande to eat hydrilla weeds.

The two agencies agreed on using brand name herbicides containing diquat and glyphosate and copper-based Komeen. The herbicide recommendations had been specified in a National Water Commission in Mexico letter sent last year to the U.S. sector of the International Water and Boundary Commission.

Chilton said Texas Parks and Wildlife wouldn't use any herbicides not approved by the EPA or by Mexico's EPA equivalent.

"We don't want a fish kill in international waters," he said. "So, I ordered the brand names that Mexico had mentioned in the letter."

The Komeen and diquat applications will be applied in a pilot plot in the river, away from the municipal water intake pumps. The pilot plot is to determine the appropriate treatment rate, Chilton said.

Hydrilla also is beginning to become a concern in the stretch of river between Falcon Lake and Amistad National Recreation Area, where it has been prolific for about a decade.

Although hydrilla and water hyacinth are most problematic, they aren't the only non-indigenous plants affecting the river's water flow.

Salt cedar and river cane also are causing problems in the western part of the state, said Dr. Jack DeLoach, research entomologist with the U.S. Department of Agriculture Grassland, Soil and Water Research Laboratory in Temple.

The hydrilla plants act like straws, drawing water out of the river to create their own bank structures.

"The salt cedar has taken over native nesting areas," he said. "They've taken the place of willow and cottonwoods."

Above Candelaria in Presidio County, the salt cedar has stands as much as a mile wide, said Carlos Marin, IBWC deputy commissioner.

Currently, the river is not flowing in sections just upstream from Candelaria.

"The section at Candelaria, about 200 miles downstream from El Paso, is known as the "Forgotten River." Any water from the El Paso area is absorbed and doesn't get to Presidio."

Spraying herbicides on the salt cedar could affect the stands, DeLoach said, but reapplications would have to be conducted to prevent re-invasion.

Instead, DeLoach recommends releasing a Crete-native beetle to eat the salt cedar.

Once a beetle colony is established, then herbicidal treatments could be reduced.

Test plots near Zapata and Candelaria have been selected to release the beetle, but DeLoach is seeking permission and participation from Mexican environmental officials along the eastern part of the Rio Grande.

"I've already met with park managers from northwestern Mexico about biological control," DeLoach said.

"They're excited about it because they want salt cedar control. The salt cedar is causing environmental and water problems."