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.


 

Field Bindweed Control Requires Multiple Programs

Consistent Management Needed to Eradicate Bindweed

By Laurie Greene, Editor

Kassim Al-Khatib, professor, UC Davis Department of Plant Sciences and UCANR Cooperative Extension specialist in weed science, discussed field bindweed, a problematic weed that has the ability to regrow even with chemical and mechanical control.

“This is weed has been around for a long time,” Al-Khatib said. “It adapted pretty well to hot, dry land areas because it has a long root with a lot of reserve in it. Whatever you try to do, the plant still has reserve in the root and can regrow again.”

The weed scientist explained that bindweed is so problematic, it has to be assessed and managed every season in a variety of ways in order to control it. “If you do a mechanical control, the plant can come back. If you do chemical control, the plant will come back. If you think that you can control it with one shot or in one season, you’re going to be disappointed. This is a serious weed problem that requires a program with multiple approaches over multiple years,” he said.

Field bindweed (Photo by Jack Kelly Clark, UC Statewide IPM Program)
Field bindweed (Photo by Jack Kelly Clark, UC
Statewide IPM Program)

The weed is also difficult to eradicate, according to Al-Khatib, “because there’s a huge seed bank, plus these seeds have a hard coat, which means they can stay in the soil longer. If you try to germinate some of them this year, you’re going to have more seeds coming next year.”

Al-Khatib emphasized a multiple approach is still the best way to reach consistent, effective results. “The key point with field bindweed is to be consistent, have a program and envision what you can do over multiple years to get rid of it. Herbicide may suppress and weaken bindweed, but it is not going to control it or eradicate it. You need multiple approaches—chemical, mechanical, some biological.”

He offered that mites, if they can get established, have been found to feed on field bindweed, another example of using a multi-pronged eradication approach. Mildew can also weaken it. “The point I want to make,” Al-Khatib repeated, “is it takes a multiple approach, multiple tools, and multiple years before you get rid of it.”


Resources:

Field Bindweed, How to Manage Pests: Pests in Gardens and Landscapes, UC IPM

 

New UC IPM Program Director

Jim Farrar Named Director of UC Statewide IPM Management Program

By Pam Kan-Rice, UCANR Assistant Director, News and Information Outreach

Jim Farrar has been named director of the Statewide Integrated Pest Management Program for the University of California’s Division of Agriculture and Natural Resources. He will begin as new uc ipm program director on Oct. 1.

UC IPM works with growers and residents to protect human health and the environment by reducing risks caused by pests and pest management practices.

Farrar is currently director of the Western IPM Center, where he has served since 2013. He succeeds Kassim Al-Khatib, UC IPM director since 2009, who is transitioning to a UC Cooperative Extension specialist position located in the Department of Plant Sciences at UC Davis. There Al-Khatib will focus on his research in weed management.

“UC IPM is a widely recognized national leader in integrated pest management,” Farrar said. “I am excited to continue efforts to make IPM the standard practice for managing pests in agriculture, communities and natural areas in California.”

Prior to joining the Western IPM Center, Farrar was a professor of plant pathology in the Department of Plant Science at California State University, Fresno for 12 years.

At Fresno State, Farrar received three teaching awards. He taught courses in plant pathology, plant nematology, diagnosis and control of plant diseases, crop improvement, aspects of crop productivity, mycology, sustainable agriculture and advanced pest management. His research centered on fungal diseases of vegetable crops, including management strategies for cavity spot of carrot. During his Fresno State tenure, he served four years as chair of the Department of Plant Science and a year as interim chair of the Department of Food Science and Nutrition.

From 1995 to 1997, Farrar taught in the Botany Department at Weber State University in Ogden, Utah. At Weber State, he conducted research on rock cress plants infected with a rust fungus that causes false-flowers. This rust is closely related to a species that is a potential biological control agent for dyer’s woad (Isatis tinctoris), an invasive weed.

Farrar has published scientific papers, extension newsletter articles, and articles in agricultural industry magazines. He also wrote a chapter in the book Tomato Health Management and five disease descriptions in the book Compendium of Umbelliferous Crop Diseases. He recently completed a three-year term as senior editor for feature articles in the journal Plant Disease and was senior editor for the online journal Plant Health Progress for three years. Farrar is a member of the American Phytopathological Society and the Pacific Division of the American Phytopathological Society.

The Wisconsin native completed his Ph.D. in botany and B.S. in plant pathology at the University of Wisconsin, Madison, and his M.S. in plant pathology at UC Davis.

 

UC Davis Professor Suggests Update to Agricultural Cooperative Extension

There is a Growing Network of New Technology to Update Cooperative Extension and Help California’s Farmers

By Diane Nelson, Senior Writer, UC Davis Ag and Environmental Sciences

 

California’s growers and ranchers get their agricultural information from multiple sources in a variety of ways. Intuitively, most of us know that. But new research by UC Davis Professor Mark Lubell, Department of Environmental Science and Policy, provides empirical evidence that the state’s agriculture community relies on a network of people using new information technologies to make land-use and orchard-management decisions.

Mark Lubell, professor of Environmental Science and Policy at UC Davis (Source: UC Davis)
Mark Lubell, UC Davis Professor of Environmental Science and Policy (Source: UC Davis)

“Over the last century, agricultural knowledge systems have evolved into networks of widely distributed actors with a diversity of specializations and expertise,” said Lubell, lead author of, “Extension 3.0: Managing Agricultural Knowledge Systems in the Network Age,” research recently published in Society & Natural Resources.

Lubell and his team hope their work will help agriculture cooperative extension programs harness the potential of these evolving personal and professional networks and make them explicit components of their outreach strategies.

Extension 3.0

Since land-grant universities were created in the late 19th century, University of California Cooperative Extension has been the state’s main campus-to-community connection that delivers sound, scientific data to growers and ranchers, landowners, environmental groups, and consumers to help develop practical solutions to real-world problems. In the early days, extension specialist shared information in person, meeting with farmers in fields or coffee shops or town halls.

The system has evolved over time, as farming has become more specialized. And the systems still works, said Lubell and coauthors Meredith Niles, UC Davis ecology alumna, and Matthew Hoffman, grower program coordinator with the Lodi Winegrape Commission. But, they argue, it could use an update. They outline a case for what Lubell calls “Extension 3.0,” a modern model for agriculture extension that capitalizes on social learning, information technology, and evolving networks of expertise.

Reviewing 10 years of surveys, Lubell’s team studied how California’s growers and ranchers make farming decisions and who they turn to for advice. They learned that Cooperative Extension specialists and farm advisers are still primary trusted sources, but respondents are also influenced by pest control advisors, local leaders, commodity groups, sales representatives, fellow farmers, and others.

“Our research provides an empirical layer to support what many Cooperative Extension specialists and advisors already do,” Hoffman said. “It’s about making sure information reaches the right people in the right way at the right place and time.”

The authors are not calling to eliminate traditional extension professionals nor suggesting all current outreach strategies be converted to more modern methods like social media, webinars and smartphone applications.

“Instead, Extension 3.0 seeks to understand how personal networks and new information and communication technologies can work together,” Lubell said.

The authors recognize social media is already a part of agricultural extension, and they know they aren’t the first to recognize its importance. But they encourage extension programs to formalize social media, information technology, and network science as part of their hiring, training and outreach strategies.

“Extension systems and professionals must be experimental, adaptive and creative with program design and implementation to maximize the synergy between experiential, technical and social learning,” Lubell said.

 

Encouraging conversation

Aubrey White, communications coordinator for the Agricultural Sustainability Institute at UC Davis, says she finds news she can use in “Extension 3.0.”

“Understanding key linkages in a community or area of research can dramatically shorten the distance between knowledge-seekers and knowledge-holders,” White said. “Lubell’s article reminds us that extension is not just delivering information, but creating conversation.”

Cooperative Extension specialist Ken Tate, rangeland watershed expert with the UC Davis Department of Plant Sciences, has been a longtime proponent of collaboration and conversation.

“For me, the study reaffirms that we shouldn’t abandon what works — face-to-face meetings, for example — but we have to keep building and adopting new components. Content is the key. We need to produce good science and provide practical solutions, and then use the best means possible to make sure that information reaches the people we serve, and helps meet society’s needs.”

You can read the full journal article on the Center for Environmental Policy and Behavior website.

Plant Scientist Urges Proactive Palmer Amaranth Prevention

By Colby Tibbet, Cal Ag Today reporter

Palmer amaranth, aka Amaranthus palmeri S. watson or carelessweed, is an annual herb of the pigweed species that is native to California where it thrives and poses a serious threat to farming.

Amaranth
Amaranthus palmeri S. Watson – carelessweed (Source on USDA Website: Britton, N.L., and A. Brown. 1913. An illustrated flora of the northern United States, Canada and the British Possessions.
 

Lynn Sosnoskie, a project scientist in the UC Davis Department of Plant Sciences who focuses on weed ecology and biology, says Palmer amaranth, spotted on the edge of fields in California, is remarkably aggressive both in growth rate and spread amidst field crops. It develops a lot of wind-blown seeds that spread rapidly.”

“I would suggest that growers in the state of California be particularly diligent about this plant,” said Sosnoskie. “It is a desert annual and is particularly well-adapted to dry environments where it can out-compete, create root growth and achieve stability well. And the recent drought has only escalated the problem.”

“Preventive measures are absolutely essential before this plant becomes established,” continued Sosnoskie. “We found out the hard way in the Southeastern U.S. that Palmer amaranth produces an exceptional number of seeds; if even one plant is missed by applications or escapes regular herbicide applications, that plant can essentially repopulate an entire field.”

“So its absolutely essential that growers here and everywhere become familiar with the weed and remove all plants quickly from a field before it hits reproductive maturity and forms seed,” she said.

Sosnoskie added that some cotton fields in the south have suffered up to 50 percent yield losses and worse. “Some growers have actually abandoned their fields and haven’t harvested their cotton for those years,” said Sosnoskie.

Sources and Resources:

Illustration Source: Amaranthus palmeri S. Watson – carelessweed (Source on USDA Website: Britton, N.L., and A. Brown. 1913. An illustrated flora of the northern United States, Canada and the British Possessions. 3 vols. Charles Scribner’s Sons, New York. Vol. 2: 2. Courtesy of Kentucky Native Plant Society. Scanned by Omnitek Inc. Usage Requirements.

USDA Natural Resources Conservation Service

Palmer Amaranth

Compensatory growth and seed production: A tale of two weeds