Summer Annual Weeds Need Control Now

Avoid Allowing Summer Annual Weeds Going to Seed

By Chris McDonald UCANR Inland and Desert Natural Resources Advisor, San Bernardino County

As the summer heat is finally nearing its end, and its officially fall on the calendar, there unfortunately is a new crop of weeds flowering right now. Some of our summer annuls have started to go to seed, others are just about ready, and others are already starting to senesce. In order to manage these weeds, managers must stop the plants from reproducing. With our summer annuals that means stopping the plants from producing seeds, right about now, (or maybe three weeks ago).

However, treating a giant tumbleweed right now isn’t really my favorite activity. I’d rather spend my time treating small tumbleweeds and working more effectively and also using less labor and/or herbicides to do it in the process. (Well I’d rather not have any tumbleweed in the first place.)

If treating the weeds when they are small is more efficient and uses less pesticides, when can we treat them at the smallest? To answer this, we need to know when our summer annuals germinate. When do our summer annuals germinate? There are several different germination periods for ‘summer’ annuals. Some of our summer annuals actually germinate in the winter to early spring from January to March, others germinate in the spring from March through May.

Weeds like yellow star thistle and stinkwort germinate in the winter from January to March. Tumbleweed and goat’s head germinate in the spring (March to May). Despite their different starting times, they will all grow during the late spring and summer as small plants hiding under a crop of larger weeds or in open areas, until they get large enough in the mid-summer to grow tall and more noticeable than our long dead winter weeds.

Other summer annual weeds, like spurges (such as spotted spurge,Euphorbia maculata, and also some other spurges), can germinate throughout the spring and summer as long as the soil is moist and warm. This summer annual can be much shorter lived than the other summer annuals mentioned above. In the desert, spurges might germinate after a monsoon, in other locations they might germinate in areas that have been irrigated or receive a little extra moisture or where the soil is moist.

The summer annuals on your property might be growing right now because of insufficient weed management in the winter and the spring! Other summer annuals might have germinated with the onset of high temperatures and need to be controlled in the early summer.

This pattern does not hold true for all species and all conditions, especially if irrigation continues throughout the spring and summer, or if there is a late spring storm or if summer monsoons deliver rains early. Sometimes even some of our winter annuals which should have flowered in February to April, germinate late in the season, and flower in June. It’s unusual and it does also happen.

If you can figure out what species of summer annual weed you have, then you may be able to figure out when it germinated and prioritize your weed treatments for that time period, in the winter and spring for some species and in the heat of summer for other species. Hopefully you will save yourself some time instead of letting them all grow into bigger and harder to treat summer annuals.

2021-05-12T11:01:46-07:00October 8th, 2019|

Field Bindweed is A Struggle to Control

Field Bindweed Difficult to Manage

By Jessica Theisman, Associate Editor

Field Bindweed is a struggle in the summer months. Scott Stoddard, UCANR Cooperative Extension Farm Advisor, Merced County, discussed with California Ag Today how to manage the weed during the summer in annual crops.

“Field Bindweed is predominantly a summer weed, so we are trying to manage it more in our summer annual crops such as cotton, corn, melons, and tomatoes,” Stoddard said.

This weed has been documented back 100 years but only recently has become more of a problem for farmers.

“It did not seem to be as universally impacting people as much as it does now,” Stoddard said.

Farmers are asking themselves what they are doing irrigation-wise that impacts the weeds.

“Does drip irrigation favor this weed? Does conservation tillage favor this weed? There are all kinds of unknowns,” Stoddard explained.

Stacking herbicides can help and control the Field Bindweed.

“Herbicides in the annual crop systems are marginal and you have to stack them. You have to combine the Roundup with something like a Treflan and then combine that maybe with some applications of other herbicides,” Stoddard said.

Even with stacking the herbicides, they are still marginal. On the herbicide angle, this is one of the things that makes weeds so challenging.

2021-05-12T11:01:46-07:00July 26th, 2019|

Study: Remote Sensing of Weeds on Vineyards Has Merit

Aerial Sensing Of Weeds Saves Time and Labor

By Jessica Theisman, Associate Editor

There is a potential use of remote sensing with drones and vineyard weed management. Working on that research is Cody Drake, a senior at California State University, Fresno. He’s working with Luca Brillante, an assistant professor in the Department of Viticulture and Enology. Anil Shrestha is chair and professor, also in the Department of Viticulture and Enology at Fresno State. Drake’s research is at a vineyard in Napa County.

“The goal of my research is to make weed management practices in vineyards a little more efficient,” Drake said.

Currently, there is a lot of manpower, money, and time going into scouting for weeds and spraying.

“What we did with the drone is we wanted to map high-pressure weed zones to target spray in the field instead of spraying the entire field,” Drake explained.

This aerial scouting is hoping to become more efficient for time and labor.

“It’s all based on imagery. The drone gives us waypoints as to the areas where we need to spray. We have a company that’s called Drone Deploy, and they go through, and they stitch all the photos together,” Drake said.

Drake’s research has only been on vineyards so far, and his research has been proven to work.

“We did a 30-meter flight and a 10-meter flight, and that just shows the difference in how close you can get to identifying weeds species on the ground at a 30 meter height,” he said.

At 30 meters, it was very hard to tell which species was which. At 10 meters, the weeds were more identifiable.

“We would prefer to do another trial with a higher resolution camera. That way we can see the species, identify them a little easier and a little more efficiently,” Drake said.

By doing this, Drake and his team can pinpoint where the heavyweights are and just go spray that one area. For future research, they are going to try a camera with higher resolution to see if it can see through a denser vineyard.

2021-05-12T11:05:04-07:00April 1st, 2019|

Alkaliweed Alert! Your Help is Needed!

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.

Alkaliweed in the field.

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.

Please follow the link https://survey123.arcgis.com/share/1f4753edfd7347ce84cc81f35e65dc02     to take a quick survey on alkaliweed in your area. Your help on this important weed issue is greatly appreciated!

2021-05-12T11:05:05-07:00March 22nd, 2019|

Fresno State Student Studies Palmer Amaranth

Sami Budhathoki Finds Palmer Amaranth Can Adapt to Saline Soils

By Jessica Theisman, Associate Editor

Palmer Amaranth

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.

2021-05-12T11:05:05-07:00February 25th, 2019|

Cover Crops in Almonds Can Displace Annual Winter Weeds

Steve Haring Working With UC Davis on Cover Crops

By Mikenzi Meyers, Associate Editor

Depending on your location, cover crops can have a big impact on your fields. Steve Haring, second-year Ph.D. student in the Department of Plant Sciences at UC Davis, has been collecting research on how different climates influence the effectiveness of cover crops.

Almond Cover Crop Displacing Weeds

“As we try to design cover crops, there are a lot of different paths we can take, and it’s important to test these different things out and see what is best for the specific things we can use cover crops for in the Central Valley,” Haring said.

He further mentioned that for optimum weed control in the Valley, growers should plant in the early winter months in order to prevent annual winter weeds.

Haring worked with the UC Davis Cooperative Extension on three different sites across both the Central Valley and northern Sacramento Valley collecting data on growth rates for cover crops. He found that because the northern valley had more direct sunlight hit the ground, cover crops thrived, and as a result, weeds were minimized.

The research will not stop there, though, Haring ensured. “The study I’m working on is funded by the Almond Board, and it’s continuing for a second year and maybe a third, so we’re trying to repeat it and validate and then also sort and synthesize information because there are people working on weeds but also working on water, insect pests, pollinator health, nematodes, and call sorts of ecosystem services,” he concluded.

2021-05-12T11:05:06-07:00February 20th, 2019|

Rice Weed Meeting Taking Place on Sept. 15

Second Annual UC Rice Weed Course Scheduled For Sept. 15

News Release

This year will mark the second annual rice-specific weed course at the Hamilton Road Field and the Rice Experiment Station in Biggs, CA, on Friday, Sept. 15. The day will begin with an interactive field tour of the research plots (Hamilton Road Field), where attendees can get up close to the weeds and rice (bring your boots)! The course will include a hands-on weed identification session on emerging and mature weeds. In the afternoon, speakers will address several pertinent topics in California rice, including weedy red rice, regulatory update and how to constructor a weed management program.

The course is a collaborative effort between UC Cooperative Extension (UCCE), UC Davis and the California Cooperative Rice Research Foundation (CCRRF.)

Whitney Brim-Deforest

“Weed management in California rice is becoming increasingly complex. This course provides growers and pest control advisers with the latest research and management strategies for the California rice system” said Whitney Brim-DeForest, UCCE Rice Farm Advisor. The event is a great opportunity for pest control advisers, growers, industry, extension and interested students to gain a deeper understanding of topics that affect rice weed management.

The cost is $70 if received by 8/1/2017, $80 if received by 9/1/2017, and $90 if received after 9/1/2017 (if there is space.) The cost for students with a valid student ID is $40/$45/$50. For more details or to register, visit http://wric.ucdavis.edu and click on RICE WEED COURSE.

If you have questions, contact Whitney Brim-DeForest [wbrimdeforest@ucanr.edu or (530) 822-7515.]

2021-05-12T11:01:59-07:00May 7th, 2017|

Weedy Rice Challenges Some Rice Growers

Weedy Rice Crops Ups Again in Northern Calif. Rice Fields

 

By Patrick Cavanaugh, Farm News Director

 

In Northern California, rice growers typically prepare to start harvesting in mid-September, but some growers have endured a lot of weed pressure from weedy rice (Oryza), also known as red rice, according to Whitney Brim-DeForest, a UC Cooperative Extension Rice Farm Advisor in Sutter, Yuba, Placer, and Sacramento Counties who focuses particularly on weeds. Red rice is actually the same species as cultivated rice, but it produces far fewer grains per plant and is therefore considered a pest.

 

Brim-DeForest said weedy rice is common in the Southeast, but not in California. “We’ve been pretty lucky in California in that we actually don’t have a big problem with it,” she said. “It’s a big problem down in the southern U.S. and they have been dealing with it in for a long time; but we have had it crop up. I think the last time was in 2006, and we managed to deal with it. It somehow popped up again in the last couple of years, so we’re dealing with it again.”

 

How weedy rice reached California is apparently a mystery. “We don’t really know the source of it, to be honest,” said Brim-DeForest. “We’re investigating that through research, hopefully starting this fall,” she said.

 

Brim-DeForest said growers have few choices to control weedy rice. “Growers that have it will either have to rogue¹ it out, pull it out by hand or sacrifice that field and spray it with Roundup,” she said, “which would kill the rice as well. And, if the rice grower doesn’t know he has weedy rice in the field, it could hurt him later at the rice mill,” explained Brim-DeForest.

 

“Once harvested, the rice goes to the mill. If a certain amount of red rice bran (the outer layer surrounding the rice grain) is discovered, the mill will not accept it and could reject the entire load,” she said.


¹rogue (verb) to remove inferior or unwanted plants

2021-05-12T11:05:48-07:00September 2nd, 2016|

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.


 

2021-05-12T11:05:50-07:00August 8th, 2016|

Jasieniuk on Weed Evolution

Tracking Herbicide Resistance in Weed Evolution  

By Emily McKay Johnson, Associate Editor

 

Marie Jasieniuk, professor and weed scientist at UC Davis College of Agricultural and Environmental Sciences, discussed her groundbreaking research, “I work on the population genetics and evolution of agricultural weeds and invasive plants,” she said. “We use molecular tools to look at the origins and spread of weeds. We also use molecular tools and genetic studies to understand the evolution of herbicide resistance in weeds,” Jasieniuk added, “to be able to propose management approaches that reduce the likelihood of further evolution and spread of resistant weeds.”

UC Davis Annual Weed Day 2016

UC Davis Annual Weed Day 2016

Jasieniuk and her team identify the origins of invasive plants, and determine how they were introduced. “We study how they were introduced, how they have spread and whether they have been introduced multiple times. Again, if we understand how they’re spreading, we can do something to try to stop the spread,” she said.

Italian rye grass, a weed Jasieniuk is currently studying, is problematic because it is resistant to Roundup, a popularly used weed and grass killer by growers. “UC ANR Cooperative Extension specialist, now emeritus, Tom Lanini, and I sampled over 100 locations of Italian rye grass and tested them for resistance to Roundup ten years ago,” she said about the project, funded by USDA. “Last year, we re-sampled all of those sites, and we’re re-testing to see if there’s been an increase or a decrease or no change in resistance to glyphosate, to Roundup,” she said.

Roundup isn’t the only weed and grass killer available on the market. “We’re looking at resistance to three other herbicides,” she said. Working with growers to determine the most efficacious weed treatments that also reduce the likelihood of wood resistance to herbicides,” Jasieniuk explained, “We interview growers about their herbicide use, non-chemical approaches, and integrated management techniques to identify management practices that correlate highly with low or no resistance,” she explained.

Resistance management is found to be more effective with a rotation of various herbicides. “What you want to do is rotate different types of herbicides with different modes of action,” Jasieniuk said. “Perhaps do tank mixes and incorporate non-chemical approaches as well,” she added.

Eliminating weeds can be as simple as disking and digging them out with a shovel when there are only a few. “I think, in many cases, this would have done a lot to prevent new weeds from coming in and certainly resistant weeds from spreading,” she noted.

2021-05-12T11:05:53-07:00July 11th, 2016|
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