Information Needed on A New Plant Called Alkaliweed
By James Schaeffer, Kurt Hembree, and Anil Shrestha, Graduate Student CSU, Fresno, UCCE, Fresno County, and Professor, CSU, Fresno
Pistachio growers and consultants in the southern San Joaquin Valley have recently reported an invasion of a new plant (alkaliweed) along irrigation ditches, roadsides, and into their orchards. Alkaliweed is a California native perennial plant that seems to be rapidly spreading throughout the region.
In some cases, this weed has completely taken over pistachio orchards in a matter of a couple of years after first being spotted. Thus far, repeated applications of postemergence herbicides have only yielded minimal control effects.
Unfortunately, little information is known to date about specific biological and ecological characteristics of this weedy plant, so we are asking for your assistance to help us identify where specifically it has become a problem for you. With this information, we will better be able to understand its growth characteristics and hopefully develop control measures to mitigate the problem.
Studies are currently under way to look at some of these growth characteristics (such as response to salinity, light, and moisture). Your input of where it has become a problem for you and your growers is critical for us to be successful.
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.
Subsurface drip irrigation, a more efficient form of water delivery, is growing in popularity and utilized on a widening range of crops. Claude James Phene, a research consultant for the UC Cooperative Extension, said subsurface drip efficiency is evident with both water and nitrogen in pomegranates.
Using a lysimeter, a big box on a calibrated truck scale that measures evapotranspiration, Phene can calculate the precise water requirement for pomegranates according to the soil moisture feedback indicated by the machine. Based on these calculations, Phene can make clear water recommendations to growers so they can accommodate the needs of their plants without exceeding them.
Because it is buried and targeted, subsurface drip irrigation also helps control weeds and reduce animal and traffic disturbances.
This six-year study has also demonstrated these drip lines prevent leaching—the loss of nutrients in the soil—that occurs with other types of irrigation systems. Phene explained, “The lysimeters are equipped with a drop-tube at the bottom so we can measure the nitrogen in any output to determine how much leaching occurs and to make recommendations on fertilizer.”