What is in this article?:
- Weed shifts causing more concern than glyphosate resistance
- Weed shifts causing Palmer spread
- Glyphosate resistance grabs headlines but not a major issue in California.
- Weed shifts from herbicide use more important.
- California cropping systems different from areas where herbicide resistance is a major issue.
Mark Twain once responded to inaccurate reports of his death as “greatly exaggerated.”
The same could be said for California about one of the hottest topics in U.S. agriculture today, the rapid growth of weeds resistant to the herbicide glyphosate. California has its share of glyphosate-resistance weeds (four of the nine identified so far); however, the problem is more hype than fact in the Golden State.
Although weed scientists have identified significantly more weeds resistant to far more herbicides that are now attributable to glyphosate, it is the rapid spread of Roundup-resistance that is the talk inside and outside of agriculture.
This “super weed” issue has captured headlines in California, Renee Pinel, president/CEO of Western Plant Health Association, told a meeting of the California Weed Science Society in Monterey.
“The perception of widespread resistance to glyphosate really isn’t an issue in California, even though we hear about it a lot,” she said. One reason is California’s different cropping systems allowing for more alternatives that other parts of the country. Although growers in the West are adopting minimum tillage systems more readily, cultivation is still more prevalent than in other areas of the U.S. And there is less reliance on a one-herbicide weed control strategy in California in most all crops.
Pinel said glyphosate resistance is “not a product issue” but more about growers not using sound, multiple weed control strategies. This has been compounded by overuse of cheap off-patent glyphosate, she added.
Nevertheless, the business of California weed control continues to evolve with shifts in dominant weed species and some weeds becoming more challenging to control at glyphosate label rates, says Tulare County Cooperative Extension Farm Advisor Steve Wright, who also spoke at CWSS.
“The Roundup resistance technology is outstanding, and California growers realize the economic benefit of it,” Wright said. “You hardly see fields with nutsedge any more, and it is due to the Roundup Ready technology.” It has also helped in controlling nightshade. Wright estimates California cotton growers have saved $200 per acre per year with this glyphosate-resistant technology.
Most cotton producing states except Texas and California grow virtually 100 percent herbicide-resistant cotton varieties. One reason California has not been that high is because there has not been a Roundup-Ready Pima, the dominant cotton planted in the San Joaquin Valley. That changed last year when the glyphosate-resistant technololgy was approved for California, and 50 percent of the crop was planted to Pima Flex. This year Pima Flex acreage will likely be a much higher percentage herbicide resistant.
About 85 percent of California upland varieties are glyphosate-resistant varieties.
Although documented weed resistance to glyphosate is spreading rapidly elsewhere, Wright is more concerned about weed shifts in California than resistance.