If Roundup Ready alfalfa hits the market next year, as expected, and the tech fee isn't too high, Steve Orloff expects it to quickly become popular in California.

“It's exciting,” says Orloff, a farm advisor in northern California's Siskiyou County. “It will make weed control a lot simpler for farmers.”

Most alfalfa growers in that state routinely apply herbicides, both in the seeding year and on established stands. Their dairy and horse clients demand weed-free hay.

But in Wisconsin, chemical weed control is rarely used after the first year. Jerry Doll, University of Wisconsin weed control specialist, figures glyphosate's broad weed-control spectrum and low cost may convince more growers to spray for weeds.

Orloff and Doll are among the first university workers to test Roundup Ready alfalfa. So far they're impressed. They've found that one glyphosate treatment kills most broadleaf and grass weeds that invade alfalfa without damaging the crop, even at very high treatment rates. They like its wide application window, too.

Both planted Roundup Ready varieties developed by Forage Genetics, the company that licensed the technology from Monsanto. Doll started his research in 2000. Orloff, along with farm advisors in three other counties, first planted Roundup Ready seed in 2001.

For seeding-year weed control, the Californians compared two glyphosate rates — 1 and 2 qts/acre. Better than 95% control of nearly all weeds was achieved at all sites, Orloff reports. While the 2-qt rate killed weeds faster, it generally wasn't needed.

“One quart one time will do it,” he says.

The best time to spray is at alfalfa's three- to four-trifoliate-leaf stage, they found. Spraying at the six- to nine-trifoliate-leaf stage worked reasonably well, too. But a very early treatment — at the unifoliate stage before the crop had established much of a canopy — left it susceptible to weed reinfestation.

Glyphosate also performed well in the first year of testing on established stands.

“We didn't have high weed pressure, and we didn't have summer annual grasses come in because the stands are so young,” says Orloff. “But, on the weeds we did have, it gave excellent results.”

In Wisconsin, growers can get better seeding-year weed control with glyphosate than with current single-product alternatives, says Doll. Then it probably won't be needed again until the third or fourth year, when the stand begins to thin and weeds move back in.

“People basically live with whatever shows up in the third and subsequent years,” says Doll. With glyphosate, “it would be economical and effective to take them out, with no risk of crop injury.”

Current chemicals are effective on some weeds, but not others. Products that take out quackgrass, for example, aren't effective against dandelions. Glyphosate will control both. For best results on dandelions and other tough broadleaves, though, Doll will recommend that it be applied in fall instead of spring.

“If yellow rocket, white cockle and dandelions are the enemies, a fall application will lead to a definite boost in performance,” he says.

Doll and Orloff are concerned about potential weed shifts and weed resistance that could result from continued use of glyphosate. Orloff also wonders about customer acceptance of genetically modified hay, especially hay targeted for export.

Both believe seed costs will be a big factor in determining the popularity of Roundup Ready varieties. Alfalfa will be the first perennial agronomic crop with the herbicide-resistance gene. Monsanto won't be collecting a technology fee every year, as with annual crops, so the one for alfalfa will likely be higher.

“Alfalfa growers are very price-conscious,” Orloff points out. “Seed prices are a major consideration when they're selecting varieties. If the price of seed is twice what it is now, are they going to be willing to pay it?”