Vigilant Seed Bank Reduction for Weed Control

Vigilant Seed Bank Reduction: Whatever it takes, don’t let weeds set seed.

By Patrick Cavanaugh, Farm News Director

 

For the past 15 years, Robert Norris, professor emeritus and vegetable crops weed specialist, UC Davis Department of Plant Sciences, has continued to attend Weed Day each year at UC Davis and to contribute weed photography for CalPhotos, a UC Berkeley Digital Library Project photo database of world-wide plants, animals, landscapes, and other natural history subjects developed to provide a testbed of digital images for computer science researchers to study digital image retrieval techniques. Norris was involved with initiating the Plant Protection and Pest Management Graduate Program at UC Davis.

 

“I’ve been a botanist since I was 14 years old,” Norris said, “and I still have a lot of passion regarding weed control.” Norris has a strong and steady philosophy on weed control and it all comes down to seeds. “The last 25 years of my work, I looked at population dynamics of weeds, like seed longevity in the soil and what we call the size of the seed bank also known as the seed production by weeds. That’s really where I spent most of my time.

Field Bindweed
Field Bindweed

 

“I found that most people have a very poor idea of how many seeds are produced by a weed. This led me to question some of our current management philosophies; namely, the one that comes out of entomology—the use of thresholds (or how many weeds need to be present before treating them),” noted Norris. “I felt that for weed science, thresholds were not the way to go, and my position has been vindicated by the problems we’ve run into using thresholds.”

 

Norris offered the example, “Barnyard grasses are probably one of our most serious summer grass weeds. A small plant can produce 100,000 seeds; while a big plant, well over a million. I can remember going put in a tomato field years ago and looking at one barnyard grass plant. Because I had been working with it, I can say that plant probably put out 50,000 seeds. If you spread those seeds around an acre, that’s enough to give you serious yield loss the next year,” Norris explained. “Again, that’s one plant, spread out over an acre. Obviously its seeds wouldn’t spread over an acre [on their own], but with our tillage equipment we would move it around quite a bit.”

 

“My bottom line for about 30 years now is: Don’t let the weeds set seed. Whatever it takes, don’t let them set seed,” Norris said. If you follow that philosophy, Norris said after a while you drive the seed bank down.

 

“Many people don’t realize this, but some of our really big growers got on to it a long time ago. One farming operation I worked with for years, J. G. Boswell Co., with most of its land in Kings County. “I knew the manager in the late ’50s, into the ’70s. He now is retired now, but he came to this conclusion himself back in the late ’50s,” Norris said. “I haven’t been on Boswell’s property now for 20 years, because I retired. However, if you go down there, you will not see a weed problem, at least not like most growers.”

 

“The difficulty really is, in order to carry out this philosophy, you need to use hand labor for weed management and it is becoming less and less easy to find,” explained Norris. “Most weed management is done on a one-year one-crop basis; whereas, the type of management we’re talking about where we’re really thinking seed bank dynamics, has to be done over multiple years. Another big problem that I still see is if you miss one year, you can undo 5 to 10 years of what you’ve just been doing, because of this high seed output,” he said.


NEVER LET ‘EM SET SEED, by Robert Norris, Weed Science Society of America.


 

USDA to Help Farmers Diversify Weed Control Efforts

USDA Addresses Herbicide Resistant Weed Control

Edited by California Ag Today

 

Agriculture Secretary Tom Vilsack announced TODAY the U.S. Department of Agriculture (USDA) is taking steps to address the increase of herbicide resistant weeds in the country’s agricultural systems.

In California, glyphosate resistant weeds are found throughout the state, and growers are warned to minimize using the material back-to-back during weed control. More information can be found http://info.ucanr.org/weed_sept/.

“Weed control in major crops is almost entirely accomplished with herbicides today,” said Vilsack. “USDA, working in collaboration with the Environmental Protection Agency, must continue to identify ways to encourage producers to adopt diverse tactics for weed management in addition to herbicide control. The actions we are taking today are part of this effort.”

To help farmers manage their herbicide-resistant weeds more holistically and sustainably:

  • USDA’s Natural Resource Conservation Service (NRCS) will offer financial assistance under its Environmental Quality Incentives Program (EQIP) for herbicide resistant weed control practices that utilize Integrated Pest Management plans and practices.
  • Later this year NRCS will be soliciting proposals under the Conservation Innovation Grants (CIG) Program for innovative conservation systems that address herbicide resistant weeds.
  • USDA’s Animal and Plant Health Inspection Service (APHIS) will actively promote use of best management practices (BMPs) in design protocols for regulated authorized releases of genetically engineered (GE) crops and will include recommendations for BMPs with the authorization of field trials of HR crops.
  • USDA is partnering with the Weed Science Society of America (WSSA) and is providing funds to develop education and outreach materials for various stakeholders on managing herbicide resistant weeds. The Secretary has directed Dr. Sheryl Kunickis, Director of the USDA Office of Pest Management Policy, as the point person leading this effort with the USDA.

 

USDA works with the EPA

The issue of herbicide resistant weeds has become one of increasing importance for agriculture. When herbicides are repeatedly used to control weeds, the weeds that survive herbicide treatment can multiply and spread.

With EPA’s announcement TODAY on the registration of new uses for herbicide mixtures containing the herbicides 2,4-D and glyphosate (in the Enlist® formulation) in conjunction with new genetically-engineered crop varieties, farmers have more tools for improved management of emerging populations of herbicide-resistant weeds in corn and soybeans crops. In its decision for 2,4-D use on genetically modified corn and soybean, EPA has outlined new requirements for registrants as part of a product stewardship program.

The USDA Office of Pest Management Policy worked with EPA to address the issue of herbicide resistance through appropriate label language that will require registrants to develop a stewardship program for the herbicide, develop training and education on proper use of the product that includes diversifying weed management, investigate and report nonperformance, and develop and implement a remediation plan for suspected herbicide resistant weeds.

EPA intends to require the same stewardship plans for all new applications for product registration on genetically modified crops with the goal being to encourage effective resistance management while maintaining needed flexibility for growers.

USDA recognizes that the problem of herbicide resistant weed control will not be solved solely through the application of new herbicides. USDA has worked with the Weed Science Society of America for a number of years on identifying best management practices for farmers and on addressing impediments to adoption of those practices.

USDA will continue to work to ensure that growers have the diverse tools they need to address the management of herbicide resistant weeds.

Sources: USDA, CDFA