While those attributes are highly desirable, they also could be a recipe for glyphosate-resistant weeds. But that does not need to be so, according to Putnam.

“If you do not spray anything for weed control but glyphosate for 10 years, it is a recipe for weed resistance,” agreed Putnam, cautioning growers that they must be aware from the beginning of that potential. There are a host of non-glyphosate herbicides that can be used to preclude Roundup resistance.

“We know how to prevent weed resistance. The question is will growers adopt management schemes to prevent it?” he said.

Some growers will have to rely on non-glyphosate herbicides, since Roundup does not control or has limited activity on several problematic weeds like burning nettle, henbit, malva and filaree, said Putnam.

On the other hand, glyphosate is very good in controlling weeds like Dodder, nutsedges, quackgrass and dandelion that existing herbicides do not control.

Putnam indicated there could be plenty of tank mixes being used to control weeds in RR alfalfa. And since Roundup is a contact herbicide, Putnam expects growers to still use pre-plant herbicides like Treflan to establish stands.

There are no silver bullets in agriculture, and this new technology may not be for every grower, especially those who are satisfied with their current weed management program.

About 300,000 acres of Roundup Ready alfalfa were planted nationwide before the sales ban went into effect. About 80,000 of those were in California. Retired UC Farm Advisor Mick Canavari surveyed 24 growers about their experiences with GE alfalfa.

They all rated the technology very high in many areas, especially in situations where the RR alfalfa was planted in heavily weed-infested fields or after a crop like processing tomatoes where weeds like annual morningglory can be a major issue.

Since Roundup is a non-restricted material, RR alfalfa was selected by growers to plant where there was the potential for groundwater or surface water contamination. Surveyed growers said there were no major disadvantages to RR alfalfa.