Sami Budhathoki Finds Palmer Amaranth Can Adapt to Saline Soils
By Jessica Theisman, Associate Editor
Sami Budhathoki is in the last semester of her undergrad degree at Fresno State. She spoke with California Ag Today recently about her research on how the Palmer Amaranth can adapt to saline soils in the San Joaquin Valley. Palmer amaranth as among the most troublesome weeds in agriculture because it is a very prolific seed producer and very tough to control due to widespread glyphosate escapes. It is found throughout California.
Her major advisor is Anil Shrestha, a professor in weed science at Fresno State. Budhathoki presented her research at a recent California Weed Science Society Meeting in Sacramento.
“I treated soils with five different salt levels, and I found out that the weed likes that higher salt levels, and they did fine, and they all germinated,” Budhathoki said.
Based on the pictures on Budhathoki’s poster, the Amaranth grew better in soils with higher salinities.
“That gives us the hint that Fresno is more resistant for the Palmer Amaranth plants because the west side has a lot of salt in its soil,” she said.
That is why it is hard to control in those areas, especially because they propagate so easily.
Budhathoki gave California Ag Today more insight on her research.
“Before treating the soil with salt, the plants were all the same height and same size. After the treatment, you can see the differences in how each plant reacted to the salt,” she said.
We asked Budhathoki what it was like working with such a troublesome weed in the ag industry.
“It was my first time working with Palmer Amaranth; it was a good experience,” she said.
Budhathoki says that she thinks there will be more research on this weed in the future so that farmers can find out how to better control it.
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.
“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.
Consistent Management Needed to Eradicate Bindweed
By Laurie Greene, Editor
Kassim Al-Khatib, professor, UCDavis 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.
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.”
A team of four Fresno State plant science students took first place in the weed identification category at the 58th annual Weed Day seminar hosted by University of California, Davis.
Seniors Sarah Parry of Sonora, Isaac Giron of Terra Bella and Mala Tu of Cambodia and graduate student Rama Paudel of Nepal correctly identified 17 of 20 weeds to win the contest among almost 200 students on July 10.
Students were asked to identify different types of weeds during a tour of current weed research plots at UC Davis. The plots involved herbicide research in annual fruit and vegetables crops, crop safety and herbicide symptomology demonstrations, aquatic weeds and grassland weed invasion and restoration research.
The students were invited to a dinner after the seminar for one-on-one interaction with UC Davis weed science graduate and post-doctoral students, extension specialists and professors.
“It was a great experience that opened my eyes to new opportunities in weed science and it has encouraged me to pursue my master’s degree,” Perry said. “I’m excited to see what the future has in store.”
Each year, Weed Day brings together pest control advisors, farm advisors, chemical company cooperators, college faculty and students and regulatory officials to learn about current weed science research at UC Davis.
For more information, contact Steve Wright, farm advisor at email@example.com or 559.684.3315.