Archive for the ‘Weeds’ Category


2 PPOresistant pigweeds confirmed in Arkansas Tennessee MidSouth weed specialists have been warning that pigweeds ndash already often resistant to multiple chemistries ndash were in danger of developing resistance to PPO chemistry Those warnings have proven prophetic

The resistance treadmill – how do we get off?

Weed scientists say we can’t keep replacing one resistant herbicide with another.

Forrest Laws | May 12, 2017

How long will it take Palmer amaranth to become resistant to the new formulations of dicamba and 2,4-D that have been approved to be applied over the top of dicamba- and 2,4-D-tolerant cotton and soybeans?

That depends on what growers do to protect the new technologies, according to Bob Scott, a University of Arkansas Extension weed scientist and a speaker at the Pigposium 3 herbicide resistance meeting in Forrest City, Ark.

“If we follow on the resistance path that we’ve been following, and we just come in here and add dicamba to take care of this problem (PPO inhibitor resistance), what do you think is going to happen?” Dr. Scott asked. “We’re just going to add to our list of resistant weeds. We’re going to add dicamba to the growing list of resistance.”

Dr. Scott traced the history of the development of herbicide resistance in Palmer amaranth or pigweed in soybeans, beginning with Prowl and Treflan in the 1980s, the ALS herbicides such as Scepter in the 1990s, glyphosate in the 2000s and

the PPO inhibitor herbicides such as Reflex and Flexstar since 2010.Extension weed scientists at the University of Arkansas have already demonstrated how quickly resistance could develop to dicamba, the active ingredient in the new Xtendimax, Engenia and FeXapan herbicide formulations.

Three generations

“We proved this in a laboratory where this particular population of pigweed in just three selections using sub-lethal doses was not controlled with 16 ounces of dicamba,” Dr. Scott noted. “So we just proved that it can happen if we don’t do something to address herbicide resistance, and we’re not proactive in managing this from Day one.”

He had some words of warning about glufosinate or Liberty, which is one of the few remaining herbicides that can be applied postemergence to control pigweed – in Liberty Link cotton and soybeans.

“The last herbicide that’s put on the field is where the selection pressure occurs,” he said. “I had somebody ask me the other day about planting Liberty Link beans and putting Prefix or Zidua down and using Liberty post. But that last application they’ve been putting out has always been Liberty post, right?

“So they said ‘Is that a good enough reason to rotate to Xtend beans?’ and I said ‘absolutely.’ It’s a good reason to rotate chemistry. If it’s been working, change it. We have to rotate to change that last selection pressure that goes on that field.”

Farmers in northeast Arkansas have about a 50 percent chance of encountering resistance to PPO inhibitor herbicides in their fields in 2017, according to Jason Norsworthy, professor of weed science at the University of Arkansas and one of the organizers of the Pigposium.

Multiple resistance

But some growers are having to deal with Palmer amaranth populations that are not only resistant to PPO inhibitors but to three other groups of herbicides, as well, said Dr. Norsworthy, who holds the Elms Farming Chair of Weed Science at the U of A.

“In 2015, this field near Gregory in Woodruff County was found to contain resistance not only to the PPO inhibitor or Group 14 herbicides, but also to the ALS chemistries (Group 2), the dinitroanilines, things like Treflan and Prowl (Group 3), and Roundup (glyphosate – Group 9,” he said, referring to a field overgrown with pigweed.

“This was actually a conventional soybean field. Bob Scott did research in this field in 2015. And when you take a look at this population, we’re unable to grow Roundup Ready or conventional soybeans in this field because there is no effective postemergence option for the control of a pigweed population that has PPO resistance as well as glyphosate resistance.”

Weed scientists have now documented resistance in Palmer amaranth to the PPO inhibitor class of herbicides in seven states – Arkansas, Mississippi, Tennessee, Missouri, Illinois, Kentucky and Indiana. Norsworthy said 19 counties in Arkansas have confirmed PPO resistance.

“If you had any Palmer amaranth in one of your fields at harvest in 2016, you have better than a 50 percent chance that you have PPO-resistant Palmer in your fields,” said Dr. Norsworthy. “Folks, this is spreading, and it is spreading no different than what we saw with glyphosate. We are quickly losing one of the mainstays, especially in soybeans, from a weed control standpoint.”

Better than 50 percent

He displayed a slide of a bench top containing plants from about 40 different populations of Palmer amaranth. The plants were sprayed with 1.5 pints of Flexstar when they were about 1-inch tall.

“Anything you see that is still alive on this bench top (40 to 50 percent of the plants) would be resistant to the PPO chemistry,” he said. “Research has been conducted that shows the resistance mechanism is very similar to what you see in waterhemp in the Midwest. However, there are other PPO resistance mechanisms in this population that are much more resistant to the PPO chemistry than in some of the other pigweeds out there like waterhemp.”

Dr. Scott said that once resistance occurs that herbicide is lost to producers whether it’s glyphosate, Treflan or Flexstar.

“There’s no fitness penalty for the most part,” he said. “Some resistances have fitness penalties – the weed is damaged by the herbicide so it’s less competitive – but in pigweed it just seems to make it stronger the more resistant it gets.”

The threat of multiple resistance or resistance to more than one class of chemistry is frightening, Scott says. “I’ve had people calling me wanting to know where they can buy a good hoe, and that’s not my idea of weed science.”

Change it if it’s working

He said overlapping residual herbicides, rotating chemistries – even when the current herbicide is working – and using cultural practices will all be needed to preserve any new chemistries or traits growers may get in the years ahead. And growers need to treat the new traits – Xtend, Enlist and the new Balance trait that is expected to be approved in the near future – as if they were new herbicide chemistries.

Dr., Scott also called on herbicide manufacturers to help growers “do the right thing” economically when it comes to helping growers avoid overusing the currently available herbicide tools.

To read more about herbicide resistance-fighting efforts, click on http://www.deltafarmpress.com/cotton/odds-not-arkansas-growers-favor-ppo-herbicides-2017

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Iowa farmer

2017-05-06T20:00:00Z Non-herbicide tactics help manage weeds Iowa Farmer Today
May 06, 2017 8:00 pm

Editor’s note: The following was written by Lizabeth Stahl, Jared Goplen and Lisa Behnken, University of Minnesota Extension educators, for the university’s Minnesota Crop News website.

Weed management tools can be divided into three main categories: mechanical, cultural and chemical. Historically in conventional systems, chemical control options, or herbicides, have been relied on heavily.

Herbicide-resistant weed populations, however, are limiting herbicide options and effectiveness in many fields. Implementing non-chemical options, such as cultural and mechanical control tactics, can help make weed management systems more effective and durable.

To develop a more robust weed management program, consider the following three key strategies:

Account for weed emergence patterns

Weed emergence is driven by a number of factors, including temperature, light, nitrogen and/or chilling period, depending on the species.

University of Minnesota trials at Waseca in 2016 showed that delaying soybean planting until May 19 resulted in pre-plant tillage removing nearly 49 percent of the giant ragweed that emerged over the season. Soybean yield potential was still around 94 percent of optimal at the May 19 planting date, based on long-term research results, and the benefit was a much lower population of giant ragweed to control post emergence.

Soybean yield potential of the early planting date averaged 99 percent of optimal, however, pre-plant tillage removed less than 8 percent of the giant ragweed emerged over the season.

Pre-plant tillage can be an effective weed control tool, especially when planting is delayed. Flushes of early-emerging weeds, such as giant ragweed, common lambsquarters and winter annuals, can be taken out with pre-plant tillage, but be sure tillage is aggressive enough to destroy the weeds, and not just uproot and transplant them.

In contrast, waterhemp emerges later in the season, typically emerging over an eight to 10 week time period. This is why residual herbicides or the layering of residual herbicides (e.g. an application at planting and then 30 days later) is recommended for control of waterhemp.

Manage the weed seedbank

Seed production of weeds can vary significantly by species. Giant ragweed, for example, has been found to produce from 1,800 to 10,000 seeds per plant, while waterhemp can average over 350,000. Although competition with other plants can reduce seed production, dense weed populations have the potential to produce tremendous amounts of weed seed.

Common lambsquarter is a long-term survivor in the weed seedbank, and according to the University of Michigan, it takes an estimated 78 years to see a 99 percent depletion of the seedbank.

In contrast, University of Minnesota research demonstrated the giant ragweed seedbank could be depleted 97 percent in two years. University of Illinois research found the waterhemp seedbank could be depleted by more than 99 percent in 4 years.

Burial of seed by tillage can increase longevity in the seedbank, while seed left on the soil surface can be lost to predation and decay. For this reason, delaying tillage as long as possible in areas where weeds went to seed could help reduce long-term weed management challenges. Avoid deep tillage, which enhances seed longevity.

Not running the combine through a weed patch will help limit the spreading of weed seeds throughout the field. Also, manage weeds along field edges to help prevent buildup of the weed seedbank.

Incorporate sound agronomic tactics

Ensuring the crop is as competitive as possible (e.g. adequate fertility, planting population and disease and pest control) can help enhance weed control. Narrow rows, expanding crop rotations and cover crops have the potential to aid in weed control as well.

Cultivation is another effective tool, allowing you to remove weeds without setting back the canopy as some postemergence herbicides can, leading to faster canopy closure and a more competitive environment for weeds.

Cultivation was evaluated in Minnesota research trials in 2015 and 2016. A preemergence application of Boundary was followed by either Liberty or mechanical cultivation. In 2016, final waterhemp control was significantly better with the Boundary/Cultivation treatment (98 percent) compared to the Boundary/Liberty program at 89 percent.

Copyright 2017 Iowa Farmer Today. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.

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USAID logo                                            IPM IL Logo

Parthenium hysterophorus L. is a native plant of tropical and sub-tropical South and North America that adversely affects food security, biodiversity, and the health of both humans and livestock in East Africa. In East Africa, Parthenium reduces the yield of many major crops such as sorghum and corn, competes with preferred pasture species, and, when consumed by domestic animals, taints their milk and meat, thereby reducing their value. It also causes human health problems such as severe contact dermatitis and respiratory problems. In addition, because of its ability to release toxic chemicals, Parthenium can replace natural vegetation, thus adversely affecting plant biodi­versity.


Zygogramma bicolorata, a leaf-eating beetle on Parthenium

In July, Zygogramma bicolorata, a leaf-eating beetle that feeds on Parthenium, was released at several sites around Wollenchiti, Ethiopia. The sites included a farmer`s field, a big uncultivated and a fenced area nearby a railway. The released Zygogramma, especially the second generation, has begun causing damage to Parthenium in cultivated as well as in non-cultivated areas. We are encouraged by the rapid establishment and spread of Zygogramma. Wollenchiti this year received heavy rain and that resulted in lush growth of Parthenium, which is ideal for the bioagent. Fencing the release plots also allowed Zygogramma to have adequate time to build its population before spreading to surrounding fields.

Zygo release site Site 4 Sept. 7 2016.jpg

Zygogramma defoliated Parthenium in foreground. Near Wollenchiti, Ethiopia, September 7, 2016.


Zygogramma defoliated Parthenium  (brownish plants beside fence)

This release was done through the “Biological control of the invasive weed Parthenium hysterophorus in East Africa” project led by Virginia State University, which has been awarded a grant of $748,465 by USAID through the Integrated Pest Management Innovation Lab managed by Virginia Tech. The goal of the project is to build on the accomplishments of the two previous USAID IPM IL-funded Parthenium projects to abate the spread and impact of the weed in east Africa. One of the objectives of the project is to scale-up the rearing and release of approved biocontrol agents, Zygogramma along with the stem boring Listronotus setosipennis in Ethiopia.

Wondi Mersie, Ph.D.

Associate Dean and Director of Research

Virginia State University

Petersburg, VA 23806





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Diversity disrupts evolution: The future of global weed management


 More services15
  Updated 14 Sep 2016, 3:38am

With a declining amount of chemical innovation in the weed management industry, it is expected a mix of technology, farming practices, and herbicides will be the keys to the future of weed management.

Diversification was the message at the 20th Australasian Weeds Conference in Perth this week, with growers facing increasing weed resistance to herbicides, and an industry that has not been able to keep up.

There has been a decrease in patent filings and product launches, and no new modes of action for over 20 years in the herbicide industry — but this does not discourage head of weed control research for Bayer Crop Science, Dr Marco Busch.

“I’m really excited about the opportunities,” Dr Busch said.

“If you identify the issue, you can do something about it.”

And for Bayer Crop Science, that means the development of new products — a process which can take up to 10 years.

So what can be done to tackle herbicide resistance in the meantime, and for the future?


“Herbicides are not the only tool the farmers have at their hand, there are all those agronomical tools,” Dr Busch said.


With technology advancing, new tactics are required to provide longevity to the current and future herbicides on the market.

General manager of crop protection for the Grains Research and Development Corporation, Dr Ken Young, believes the Australian grains industry is “at the beginning of a new dawn” where growers are becoming more receptive to incorporating new tactics into their farm plan.

“That can be crop cultivation, through to cultural management through row spacing, row orientation, through to the new technologies that are coming through where they can use microwaves or targeted tillage to control their weeds,” Dr Young said.

Dr Young believed the increasing cost of weed management in the Australian grains industry was the catalyst for this “new dawn”.

“In the past, herbicides have worked extremely well, and been very cost effective, very cheap relatively,” he said.

“And it’s only until that system’s not working we have to look for other answers, and that’s what the case is.”

Earlier this year the GRDC commissioned a report into the cost of weeds, and found there had been a “huge increase of the costs of managing resistant weeds”, to $3.3 billion annually in expenditure and yield loss, costing Australian grain growers an average of $146 per hectare.

“Growers look at that additional cost and say ‘what else can I use to manage that? And if I’ve got to pay an extra $60 a hectare to manage my weeds, what can I use that $60 for? Is it best of using a herbicide? Or is it best of using harvest weed seed management to do it, and getting longevity of my herbicides as well?’,” Dr Young said.

Australian innovations competing internationally

Compared to our overseas counterparts, Australia is thought to shape up relatively well when it comes to innovation in weed management.


Director of the Australian Herbicide Resistance Initiative (AHRI), Professor Stephen Powles, believes this comes down to necessity: where there are issues, there is innovation.

“We’ve had to be [leaders], because of the massive herbicide resistance problems we’ve had,” Professor Powles said.

“And as a result, we’ve developed some technologies in Australia that have not been developed elsewhere.

“Especially what we call ‘harvest weed seed control’ (HWSC).”

Professor Powles said most Western Australian farmers were using a form of HWSC, which targeted weed seeds during harvest to minimise the seed bank.

“We all should be proud of that work that’s been home grown Australian research,” he said.

“Our agronomists are very good, our farmers are very, very good, our farmers are excellent farmers, so we’ve got a lot to be proud of in the area.”

However despite home-grown developments such as HWSC, Professor Powles believes Australia will remain reliant on technology developed overseas.

“The herbicides that are used here are not developed here, they’re developed by the small number of corporations because of the huge research effort that’s required,” he said.

“It’s a combination of international technology and how to make it work in Australia.”

Topics: weeds, crop-harvesting, agricultural-chemicals, agricultural-crops, perth-6000

First posted 14 Sep 2016, 3:06am

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July 26, 2016 4.52pm EDT

The mesquite tree was introduced into South Africa to aid farmers and local communities. It is now invasive in most parts of the country. Shutterstock

One such tree genus, Prosopis, or mesquite, originally from the Americas, has been introduced to more than 100 countries. It was introduced into the arid parts of South Africa to aid farmers and local communities with fodder production, provide shade for livestock and produce firewood.

It has now invaded large parts of the country and has become the second most widespread invasive tree after Australian acacias. It has had a negative impact on biodiversity, livestock production, land value, human health, infrastructure and water supply. These are all crucial factors for the economy and for local people’s livelihoods.

The negative effects of these invasions have led to the initiation of programmes to manage them across the world. In South Africa the Working for Water programme drives management on state and private land along with input from private landowners. Without active management these invasive plants would become more widespread and their impact on people and the environment would be more pronounced.

Reducing the impact

Management initiatives, such as Working for Water, aim to reduce the impact and spread of invasive plants. In South Africa the initiative also aims to create jobs and drive rural development.

We recently conducted a study to assess the barriers that impede the effective management of widespread Prosopis invasion. More than 100 barriers were identified in the study, which tried to identify the problems that hinder current management operations. The results could be used to come up with solutions about how to overcome these problems.

Prosopis invasions in South Africa: a blessing or curse?

The key barriers identified were:

  • Using versus removing the tree and control options. Some parties wanted to continue using Prosopis for fodder and fuelwood and did not want them removed. Others pointed to the serious negative impact they have. There was also controversy about labour-intensive management, which is time consuming and makes progress slow. Mechanical and biological control approaches are obviously faster but employ fewer people.
  • The ecology of the species. It is hard to control because it grows very fast and spreads rapidly. It is also capable of regrowing from cut stumps if herbicide is not applied correctly.
  • Poor planning and prioritisation. Often no systematic control strategy is followed.
  • Coordination and cooperation, which is linked to poor planning, inefficient management, corruption and lack of collaboration between different government departments and farmers.

There were differences in how the importance of some barriers were perceived. Most farmers – 80% – placed high importance on a lack of planning and poor management as important barriers. Few managers – 20% – regarded these as important. This reflects different views about the context in which management projects operate.

Adaptation responses

Many of the barriers can be overcome and ways to do this were identified in some instances. But not all were conducive to simple solutions.

Key adaption responses include the adoption of more effective clearing methods. These include:

  1. Mechanised options and biological control. These are more time and cost effective but can still allow for job creation.
  2. Raising awareness and building partnerships to ensure that different actors work together to control the problem.
  3. Ensuring landowner follow-up control. This will ensure state investment is not wasted and long-term control is guaranteed. It is also legally binding but not enforced.
  4. Improved monitoring to get an understanding if control is working and of its benefits. This can also help to reduce inefficient management.
  5. Incorporating systematic strategic planning at various levels to ensure the limited funds available are spent wisely and in a way that has the most benefit.

All of this will improve the effectiveness of control programmes with the funding available.

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Solving the weed problem: Farmers use multipronged approach to fight pests’ herbicide resistance

With “bulletproof” weeds like palmer amaranth and kochia becoming ever more resistant across the Great Plains, farmers must focus on rotating modes of action, using pre-emergent herbicides and following the label when mixing products, experts say.

For 25 years, kochia and other weeds were successfully controlled by glyphosate, a broad-spectrum herbicide initially sold under the brand name Roundup. Now, these weeds are showing resistance to the herbicide in fields from Texas to Canada, according to Kansas State University.

“We were in the honeymoon period of weed control in the late 1990s and early 2000s when glyphosate was working,” said K-State weed scientist Curtis Thompson.


Some farmers are pulling out the tillage equipment, said Thompson. But if they can, there are more advantages to sticking with a no-till system.

Research conducted by Dr. Alan Schlegel at K-State Southwest Research and Extension Center at Tribune shows 13-year average yields of wheat/sorghum/fallow benefit from a straight no-till system, Thompson said. The research compares three systems: conventional, reduced tillage (ground is only tilled as needed between sorghum harvest and wheat planting), and complete no-till. Sorghum hybrid, soil fertility and in-crop weed control remain the same in all three systems.

The results: the 13-year average yield of wheat that was conventional – 13 bushels an acre; reduced tillage – 16 bushels an acre; and no-till – 21 bushels an acre. The 13-year average yield for sorghum was: conventional – 18 bushels an acre; reduced till – 30 bushels an acre; and no-till – 58 bushels an acre.

“I do think it is going to require a higher level of management in all phases of crop production,” he said of sticking with no-till. “I think it can be done.”

“Timeliness of effective herbicide applications is key so successful control,” he added. “It may mean that we apply herbicides in late fall or in January or February to control a severe kochia population, or perhaps fall applications to manage marestail.”

Crop rotation is also a key component, which allows the use of multiple modes of action of herbicides and different timings of application based on the crop planted, Thompson said.

“We aren’t ready to throw out the no-till technology and go back to the moldboard plow,” he said.

Pre-emergent herbicides

Terry Faurot, a Scott County farmer and chemical applicator, said his business has been busier due to the growing resistant-weed problem – and he’s busier earlier in the season.

“Farmers are jumping in early,” he said. “In the January to March range, I’m putting on pre-emergents.”

He advises farmers to follow a course of action that catches the weeds before they come out of the ground.

“What farmers are doing, they are coming in February and March and putting something like Dicamba and Atrazine, and creating a barrier. So, when the ground warms, it blocks (the weeds).”

Then, he said, as the herbicide wears out and it gets closer to planting, farmers can come back with another pre-emergent herbicide.

“The whole thing is to keep it from seeding out,” he said. “The biggest thing is to not let those weeds go to seed.”

Killing a growing weed crop

If kochia does emerge, don’t wait until the weeds are tall to try to kill it, he said. “Then they are really hard to kill.”

The best time to kill growing kochia is when it’s between 3 and 8 inches in height. Once it gets too tall, the stem gets woody and the plant won’t take in the chemical.

For palmer amaranth – or any weed – the earlier farmers catch them, the better.

Other modes of action

Faurot also recommends that farmers change up their mode of action.

“I usually spray with three modes of action to attack weeds,” he said, adding many farmers use a combination of 2,4-D, Dicamba and glyphosate.

But there are others. For instance, mixing atrazine and paraquat is a good combination for controlling weeds in the fall. Paraquat is a potent chemical and it defoliates the plant, Faurot said.

“I wouldn’t go with the same stuff all the time,” he said.

He also recommends mixing in ammonium sulfate to the tank mix, as well as surfactant, an additive that will help farmers get better coverage.

Also, don’t cut back on chemical. Follow the label. Once you damage the weed, it becomes even tougher to kill.

“You just can’t skimp on chemicals,” Faurot said. “You have to kill those weeds the first time around. If you damage it, you won’t kill it the second time around.”

Sometimes it is better to invest in more expensive chemical, he said.

“Sometimes it it is cheaper to put on the expensive stuff the first time than come in and do a rescue treatment later,” he said.

What other producers are doing

In Reno County, farmer Jud Hornbaker is using different mixes of chemicals to combat weeds. That includes the herbicide Sharpen for pre-plant burndown. For post emergence, he uses Anthem and Roundup.

Next year he will have Liberty in the tank mix, another post-emergent herbicide. He also uses Warrant, 2,4-D and Dicamba. He uses about 17 to 20 gallons of water an acre.

“The main thing is to get the weeds small, not wait until they are 3 feet high,” he said.

McPherson County farmer Monte Dossett also has several different modes of action to combat Palmer amaranth pigweed, including pre-emergent herbicide Authority and Zidua.

He has also used Fierce and Warrant. The chemicals work best when he can maintain soil moisture. The water in the soil helps make them work.

He applies a pre-emergent a month before planting and right after planting – along with Roundup once the plants emerge.

Some chemicals have gone up considerably, Dossett said.

“Before the weed resistance, I’d do one pre-emergent, and a lot of people wouldn’t do any,” he said.

Kansas Agland Editor Amy Bickel’s agriculture roots started in Gypsum. She has been covering Kansas agriculture for more than 15 years. Email her with news, photos and other information at abickel@hutchnews.com or by calling (800) 766-3311 Ext. 320.



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Green Invasion: Destroying Livelihoods in Africa [Video]

To see videohttps://cabiinvasives.wordpress.com/category/ecosystem-services/

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