Invasive whitetop is on the menu for woolly grazers in northern Nevada
Dirty cap sheltering his sun-reddened face, Wayne Jesco, 32, whistles for attention.
“Come on, girls.”
One of the black-faced Suffolk ewes, age 2, moseys his way.
Jesco’s trimmed blond moustache curves around his mouth and trails down to his chin. This pasture on the University of Nevada Main Station Farm, he explains, was the testing ground for the first livestock weed control experiment in Nevada four years ago.
Soon the herd follows the first ewe, stirring a dust cloud in its wake. Through the haze, they munch on the pasture’s greenery. These ruminant mammals are the latest weapons in Nevada’s battle against imported weeds.
Tall whitetop, also known as perennial pepperweed, is the new component of their diet. It is clustered in islands amid a sea of ruddy dirt. The pesky weed is one of 47 species in Nevada considered invasive by the Department of Conservation and Natural Resources.
Because of deep taproots and high tolerance to saline conditions, tall whitetop and other invasive weeds threaten such native plants as greasewood and sagebrush by bereaving them of water, says Lori Bellis, Nevada Department of Agriculture weed management coordinator. The weeds destroy natural habitats for indigenous animals and can upset an ecosystem’s balance.
“We have a horrible problem with tall whitetop in the Truckee Meadows,” says Becky Stock, communications manager for the Nevada Land Conservancy. “It creates a monoculture—nothing else can grow where it grows.”
Though it flourishes near water, the weed does not stabilize riverbanks. It also provides minimal nutrition for animals compared to other vegetation.
There’s no upside to the whitetop invasion.
People created the problem; now people must correct it.
Tall whitetop seeds were probably mixed in with sugar beet seeds transported to the United States from Eurasia more than 100 years ago, says Dawn Rafferty, an invasive-weed specialist.
Prior to the 1997 flood in northern Nevada, only 10 or 20 acres around the Truckee Meadows were infested with tall whitetop, says Hudson Glimp, 65, a UNR agriculture professor and co-leader of the first tall-whitetop grazing experiment. Now the weed covers more than 25,000 acres. One of the consequences, he says, is that agricultural production is down by half on Indian reservations.
Chemicals can be used to control tall whitetop. “But then nothing will grow for two or three years,” Glimp says. “You’re, in effect, sterilizing the ground.”
Moreover, he says, chemicals are sometimes forbidden because of endangered or threatened species in the area, such as the cui-ui sucker fish or the Lahontan cutthroat trout.
The best way to control tall whitetop, Glimp says, is to never let it go to seed. He stresses allowing livestock to graze the weed three or four times a growing season.
“Sheep will get fat off it,” he says. Sheep and other ruminants render seeds unviable. In fall, when weeds begin storing nutrients in their roots, a mild herbicide can be used to kill the remaining plants.
But is anyone following Glimp’s advice?
“We’ve got a disaster on our hands,” he says, “and no one seems willing to face up to it. Some of the greatest villains in this are the city, the county and developers.”
For example, he says, what used to be the Double D Ranch sold out of bankruptcy to a private developer, who paved over and built on the land. The 2,000 acres that were left unpaved are now filled with tall whitetop.
What Nevada needs, Glimp says, is enforcement of its weed-control statute. Similar to laws in many states, Nevada Revised Statute 555 declares it illegal for any person to permit an invasive weed to propagate or go to seed on his land.
"[Without enforcement,] it is nearly futile for farmers downstream to try to control tall whitetop because developers are putting seed upstream,” Glimp says.
The use of livestock to control weed infestation is promising, but there is a hitch.
“Animals will not eat [tall whitetop] unless they’re starving or trained to eat it,” Bellis says while driving east of Reno. “They probably could not survive on tall whitetop alone.”
She parks her teal Chevy Cavalier at a field near a Sierra Pacific Power Co. plant. The field is an inert dried-out monoculture of the weed. In mid-June, a new year’s growth will blossom like a blanket of snow.
Depending on the purpose of the land, duration and size of infestation, money and manpower, she says, the situation will dictate the solution.
“A whole toolbox of options” is available, she says.
“I’m not against herbicides, grazing, burning, cultivation, bio-controls, anything,” Bellis says. “I think we need to look at all the options we have and combine them in a way that’s the most environmentally friendly to get rid of an invasive species.”
Bio-control is a last resort for controlling an invasive weed—to be deployed when every other method has failed. It’s being considered for tall whitetop, Bellis says. The method involves importing the organisms that kept a weed in check in its native country—"usually a suite of herbivores, insects and pathogens,” she says.
However, bio-control for tall whitetop probably won’t be approved by the United States Dairy Association for at least 10 more years. Since the weed is in the same family as broccoli and cauliflower, high crops just over the hill in California, the USDA must be certain that whatever eats the tall whitetop will not eat the crops.
Of the remaining options, grazing seems the safest and most sensible.
In Las Vegas, goats rather than sheep are controlling weeds, says Mark Hill, who works for the Nevada Division of Forestry. Rather than going after tall whitetop, the goats’ purpose is to mow down Russian knapweed. As described by Glimp and Bellis, the animals are part of an overall program. They eat the bulk of the Russian knapweed, Hill says, after which less potent and smaller amounts of herbicide are required.
Goats have a diverse palate. Whereas sheep prefer grasses, goats will eat brush, leaves—just about anything. They also strip bark from the tamarisk tree, or salt cedar—considered invasive because of its abundant root system that absorbs more than its share of water for a desert region.
The disadvantage of goats is that a herder must be present to prevent the animals from destroying everything in sight. That increases the cost of goat use.
Whether goats or sheep, livestock are now being used for weed control throughout the United States.
“Sheep are amazing on kudzu,” Stock remarks, referring to a weed that infests the Southeast.
Perhaps Jesco has a place in his heart for goats, but for the time being, he devotes his attention to the Suffolks. Back at Main Station Farm, they crowd around as he spoils them with alfalfa pellets.
“Watch it," he says. "They might maul you from friendliness."