SKULL VALLEY, Utah — The black spears, no longer than a baby’s eyelashes, protruded in a row from the seeds that nodded on the end of the grass stalk. Susan Meyer held the cheatgrass stem with one hand and pointed them out with the other.

“These little marching armies of toothpicks here, that’s it,” Meyer said, “That’s the black fingers of death.”

Her work these days is centered on figuring out how this fungus, which looks like a miniature mohawk haircut, does its lethal work on cheatgrass — perhaps the most disruptive invasive plant in the country — and how to help the tiny spears do more of it.

Black fingers, the fungus with the horror-movie handle, is the new artillery being fired at cheatgrass, a weed that has remade the landscape of the Intermountain West. It has eliminated large concentrations of sagebrush and other native shrubs and perennial grasses by always being first.

It germinates first, uses available moisture first, burns first and is the first to reappear in damaged landscapes.

“Cheatgrass is a very insidious kind of biotic virus,” said Stephen Pyne, a Western fire historian at Arizona State University. “It takes over and rewrites the operating system. Because it grows earlier, it can burn earlier,” then in its regrowth “drive off all the other competitors. That makes for a complete overthrow of the system.”

Mike Styler, head of the Utah Department of Natural Resources, said simply: “It’s changed the entire ecology of the West.”

But the black fingers of death — Pyrenophora semeniperda — might help restoration ecologists reclaim some beachheads in the vast swath of land conquered by cheatgrass.

How much territory has become home to only a monoculture of cheatgrass, or is at least dominated by it? Estimates have been as high as 60 million acres, though most scientists now put the total at perhaps one-third of that. What is of greater concern is how much it could spread, and how fire cycles have changed since cheatgrass made its way here from Europe, probably carried in bags of wheat seeds. No one is certain when it arrived, but farmers were complaining about it more than 100 years ago.

An unpublished paper by Jennifer K. Balch of the Penn State geography department shows that fires occurred four times as often in cheatgrass landscapes in the West as in all other types of ground cover combined. The paper, which has been accepted by the journal Global Change, says that cheatgrass was a factor in nearly 25 percent of the 50 largest Western fires in the 1990s.

For decades, scientists have been trying to stop its advance, to little effect. Now Meyer and a few other scientists are exploring biological warfare. The new weapons, all fungi, are being tested in Skull Valley, a place so thick with cheatgrass that a stubbly, bleached-blond carpet of it stretches to the hills on all sides.

The experiments depend on a fine-grained knowledge of the weed’s behavior. James McIver, an Oregon State University scientist who heads an interagency federal research effort on restoring sagebrush ecosystems, explained that cheatgrass — so called by farmers whose wheat yields dropped when it gained a foothold — “gets into interstices in the sagebrush plant, grows right under the sagebrush.”

Cattle, McIver said, prefer native perennial grasses, eating them when possible and leaving cheatgrass alone. In addition, said Rory Reynolds of Utah’s natural resources department, the plant’s natural rhythms give it an advantage in arid regions. Its seeds germinate in the fall instead of spring, and it begins to grow as the snows melt, getting to the precious moisture long before native plants and shrubs.

This is a crucial advantage in the high desert areas of Idaho, Nevada, Oregon, Utah and Washington, where native plants depend on scarce water resources later in the spring. It is less of a factor in moisture-rich areas to the east. Cheatgrass grows throughout the contiguous United States but poses no threat to native vegetation outside the arid West.

The black fingers fungus, which like cheatgrass is native to the Eurasian steppe, attacks the cheatgrass seeds before they germinate. Robust cheatgrass plants can cover a square yard with as many as 25,000 seeds. “If we can get that down to 300 seeds, we consider that a successful bio-control,” Meyer said.

The black fingers fungus does its work in early spring, before the plants’ seeds are spread. That gives scientists a fighting chance in trying to restore native bunchgrasses, such as crested wheatgrass, and sagebrush and shadscale, the bristly ground cover of most of the high deserts in the 1800s.

After a successful application of the fungus, Meyer said, “crested wheatgrass seedings do not revert to cheatgrass.”

But black fungus is not uniformly lethal to cheatgrass seeds. Like a lion preying on antelope herds in the savanna, it eats the laggards — in this case, seeds that are slow to germinate or remain dormant into the spring.

Financial support for the fungus research has come from the Joint Fire Science Program of the National Interagency Fire Center in Boise, which just increased its support of Meyer, to a total of $777,000. That is part of at least $5.2 million in federal research dollars spent on cheatgrass control since 2007.

“I think we can get a biocontrol plan going in the next five to 10 years,” Meyer said. “But there are a lot of other questions.” Chief among them: Will private industry want to collaborate with government and academic scientists, and will there be enough of a market for such an effort to be worth the trouble?

The pressure to control cheatgrass is increasing. Creatures that depend on the sagebrush habitat are severely stressed; helping them could mean curbs on ranching and drilling from Arizona to Oregon.