#New weapons on the way to battle wicked weedsa somber picture of the struggle against super-weeds emerged today as scientists described the relentless spread of herbicide-resistant menaces like pigweed
and horseweed that shrug off powerful herbicides and have forced farmers in some areas to return to the hand-held hoes that were a mainstay of weed control a century ago.
The reports on herbicide resistance and its challenges and how modern agriculture is coping were part of a symposium on the topic at the 246th National Meeting & Exposition of the American Chemical Society (ACS) the world's largest scientific society.
Costs of weed control have doubled or more in some areas and crop yields have suffered according to experts.
The problems associated with herbicide-resistant weeds are spreading and intensifying especially weed species resistant to multiple products including the mainstay of 21st century agriculture the herbicide glyphosate said Bryan Young Ph d. who spoke at the symposium.
More than 200 individual weed species have been confirmed resistant to at least a single herbicide with infestations covering millions of acres in the United states and 60 other countries.
Weed management in corn has become more and more difficult in recent years due to herbicide-resistant weeds.
or snow thistle that home gardeners visualize at the mention of weed. Rather the battle involves nightmares like Palmer amaranth pigweed
which has been termed the master blueprint for the perfect weed. Under good conditions Palmer amaranth grows an inch
Young said that growers are responding to such challenges by integrating alternative herbicides into their weed control programs herbicides that work a different way
They also are turning to herbicides that have residual activity in the soil preventing weed seeds from growing into a new generation of weeds.
When those measures fail farmers are turning to cover crops to block weed growth and tilling the soil to kill emerged weeds
or bury viable seeds deep below the soil surface. Herbicides however remain the most effective tools for managing weeds in terms of overall control and for cost efficiency Young emphasized.
They have other benefits such as reducing the need for plowing and other soil tillage --which is costly in terms of energy use
They include new herbicide formulations that work in ways that sidestep the resistance mechanisms in today's weeds.
or herbicide-resistant crop traits don't create herbicide-resistant weeds Young said. Rather the use and management of these technologies to gain control of weeds by practitioners determines the risk of herbicide-resistant weeds evolving.
We need to be better stewards of herbicides to reduce the impact of herbicide-resistant weed species. Story Source:
The above story is provided based on materials by American Chemical Society (ACS. Note: Materials may be edited for content and length h
#Weeds threaten carbon offset programsresearchers have identified gamba grass and other invasive weeds as a potential threat to landholder involvement in environmental offset programs such as the Carbon Farming Initiative.
Strategic savanna burning is one way to reduce Australia's carbon emissions and create new markets in northern Australia
but the increased fuel load and emissions from weed infestations could make it unfeasible. Dr Vanessa Adams says that late dry season wildfires in Australia's tropical north generate about 3%of the country's annual greenhouse gas emissions so strategic burning could be an important abatement activity.
But when native savannas are invaded by weeds such as gamba grass fuel loads are increased dramatically and fires can burn up to five times hotter than a native wildfire Dr Adams said.
--and the costs of managing gamba grass--$40 per hectare--meaning that much more savanna needs to be enrolled for carbon farming to cover the costs of weed eradication.
and that we strategically manage weeds so that they don't become an intractable problem in the future. Story Source:
and twice became a weed--and what it means for the futurethe evolutionary biologist Stephen Jay Gould once asked
For example the weeds carry the crop form of the loss-of-shattering gene which means that they branched off from the crops sometime after people selected for loss of shattering.
Weeds stealing crop genesthe most important part of this story Olsen says is that the genetic histories of the crops
and the weeds are intertwined closely. This means the weedy forms can draw on both ancestral genes
and pull weeds growing there But on industrialized farms rice is sprouted directly in the field so there's no opportunity to remove weeds.
Because the seedlings of both weedy and cultivated rice look alike farmers often don't realize they have a problem until the field is infested really.
But that places huge pressure on the weeds to acquire herbicide resistance by hook or by crook.
So it would be pretty easy for random mutations to confer resistance on the weeds.
The other possibility is that resistance genes will migrate from the crop to the weeds.
But the crop and the weeds--which are after all the same species--could easily hybridize
It's going to change the overall composition of the weeds in U s. rice fields and presumably elsewhere in the world as well.
The despised weed makes herbicide to kill neighboring plantscontrary to popular belief crabgrass does not thrive in lawns gardens and farm fields by simply crowding out other plants.
A new study in ACS'Journal of Agricultural and Food Chemistry has found that the much-despised weed actually produces its own herbicides that kill nearby plants.
but had a hard time proving that the weed thrived by allelopathy. From the Greek allelo-meaning other
and weed science at Virginia Tech said that William Hamilton a pioneer botanist who corresponded with William Bartram
In addition the National park service's Weeds Gone Wild site has a manageable list of factsheets for some of the most common invasives.
A weed that is spreading rapidly in the Mid-atlantic states this Asian native is dispersed by seed and grows prolifically in lawns.
Meanwhile farmers looking to avoid herbicides often have to combat weeds with tillage which causes erosion.
But no-till requires herbicides to control weeds and even after adoption of the practice by many farmers harmful algal blooms were still occurring in surface waters.
because the light tilling and in-row cultivation that was done kept weeds under control. Reduced-input rotations strike a medium between conventional tillage
We've also started exchanging ideas and information with scientists facing related challenges such as herbicide resistance in weeds and resistance to drugs in bacteria HIV and cancer.
the uglier a flower or weed the more allergy-inducing its pollen tends to be.
Ragweed mugwort plantain and pigweed have more than just their unappealing appearance in common--they're some of the worst offenders to allergy sufferers said Robert Valet M d. assistant professor of Medicine and an allergist at Vanderbilt University Medical center's Asthma
Ragweed can produce up to 1 billion pollen grains per plant throughout a pollen season according to the Asthma and Allergy Foundation of America.
Of those allergic to pollen-producing plants 75 percent are allergic to ragweed. The relationship between allergy-causing pollens and their flowers is something like a beauty pageant Valet said.
In late summer and fall the weeds make their presence known. Common weed allergens include ragweed lamb's quarter pigweed English plantain and mugwort.
This year the pollen count is proving to be high in Nashville according to Valet. The pollen count may change from day to day due to an event like rain
For the analysis researchers reviewed 104 studies that looked at exposure to weed fungus rodent or bug killers and solvents and the risk of developing Parkinson's disease.
which is a common herbicide used against weeds. Relyea and his Pitt collaborators exposed the tadpoles from each of the nine populations to environments containing either no pesticides chlorpyrifos or Roundup.
while nearly 5 percent are listed as federal or state noxious weeds. Despite being nonnative and potentially invasive however these plants are still valuable genetic resources for breeding Khoury says;
This was the assertion of Prof Niels Anten in his inaugural speech upon accepting the post of Professor of Crop and Weed Ecology at Wageningen University on Monday 22 april.
In both cases plants are surrounded by numerous organisms such as weeds pollinating insects fungi blights and diseases and their natural enemies all engaged in the struggle for existence.
and Weed Ecology he will be looking at the connections between these areas of study for the benefit of sustainable crops with high yields.
Alien neighbouring plants include weeds which pose an important threat to crop production. The use of herbicides is an important element of weed control
but also harmful to the environment while more and more weeds are becoming resistant to these agents.''We will need therefore also to look at other more ecological solutions'says Professor Anten.'
'In short in order to achieve a sustainable increase in food production we will need to deploy all the weapons in our arsenal;
'Our first task was to find so-called macrofossils such as old weed seeds or pieces of grain.
Hopefully we'll find some weed seeds as they may help confirm that fertilisers were used indeed
since the type of weeds found in a field can signal whether fertilisers or some other method was used'says Axelsson.
--and it's quickly become prominent in the rocky intertidal zone of the Gulf of Maine attached to common seaweeds like rockweed or Corallina officinalis also known as coral weed.
or federal noxious weed lists are regulated and those lists are biased often toward species that affect agricultural crops.
Quinn said that a more transparent listing process would be based on a scientific process developed by the USDA known as the weed risk assessment.
unless it's on the noxious weed list said U of I professor of agricultural law A. Bryan Endres.
For economic reasons the horticultural industry has a strong incentive to keep these new plants off of the noxious weed list
Quinn first noticed the discrepancies in the regulated noxious weed lists and the nonregulated invasive plant lists
In comparing the lists from all 50 states the researchers found that Montana has a noxious weeds law that is well enforced.
If a noxious weed is found on private property it's the responsibility of the landowner to eradicate it Quinn said.
They don't want individuals to be able to go to their local weed commissioner and complain'my neighbor is going to plant Miscanthus
'and it gets added to the state's noxious weed list. That's not a good way to do business and to develop a new industrial model.
During their research and development phase they would petition the invasive species council to do the weed risk assessment on the plant that they're proposing.
I attorneys who specialize in agricultural law and Jacob Barney a weed scientist at Virginia Tech.
However some plants that are ideal for bioenergy production come with a drawback--they can potentially become invasive weeds that can cause billions of dollars in economic damage.
We did this analysis to draw attention to state noxious weed lists and to suggest ways to help prevent additional plants from escaping cultivation
Barney is an assistant professor of plant pathology physiology and weed science in the College of Agriculture and Life sciences.
According to our analysis current noxious weed laws do not provide adequate protection to prevent invasions in natural areas
This will help take the expense of noxious weed control away from taxpayers while protecting conscientious biofuels developers some of
and cultivation of 111 species of terrestrial aquatic and parasitic plants included on the Federal Noxious Weed List.
Noxious weeds on federal or state lists and invasive weeds are defined generally as plants with adverse social economic or ecological effects.
or federal noxious weed lists are subject to regulation. Since state departments of agriculture have responsibility for most regulatory bodies occasionally sharing responsibility with environmental agencies fewer plants that invade forests pastureland
The authors analyzed noxious and invasive weed species reports from each state and determined that official noxious plant lists contain on average only 19.6%of the species considered invasive by the IPCS and EPCS.
since funding for weed control is funneled generally into formally listed noxious plants. Because control is easiest in the early stages of infestation
when the political process involved in listing a weed may not have begun even the financial effects of this gap can be massive.
and more inclusive if revamped regulatory boards with input from invasive and exotic weed councils evaluated plants based on criteria such as the plant's history ecology reproductive potential and the potential for rapid spreading.
Barney earned his bachelor's degree in chemistry at the University of Kentucky and his master's and doctorate degrees in weed ecology at Cornell University.
He is a member of the Weed Science Society of America and the Ecological Society of America.
#Assembling the transcriptome of a noxious weed: New resources for studying how plants invadein order to build
Pankaj Jaiswal Assistant professor of Botany and Plant pathology at Oregon State university Samuel Fox a Postdoctoral Associate in Jaiswal's laboratory and colleagues assembled transcriptomes of a noxious weed Brachypodium sylvaticum
and is listed as a noxious weed along the West Coast of the United states. It is aggressively invasive within its current range--near monocultures of this grass occupy thousands of hectares of mixed coniferous understory
A leafy plant related to a common weed known as lamb's quarter was infected also with a virus that caused a local infection.
Seeding rates can influence a cover crop's ability to smother weeds. During lettuce and broccoli production Brennan ensured all systems received the same fertilizer and irrigation inputs and pest management.
But effectively suppressing weeds with the legume-rye crops required seeding at three times the typical rate
while rye and mustard crops appeared to suppress weeds adequately with typical seeding rates. The long-term study also provided Brennan with more data about year-to-year yield variations in the legume-rye mix including why legumes
#Clove oil tested for weed control in organic Vidalia sweet onionweed control is one of the most challenging aspects of organic crop production.
Most growers of certified organic crops rely heavily on proven cultural and mechanical weed control methods while limiting the use of approved herbicides.
A new study of herbicides derived from clove oil tested the natural products'effectiveness in controlling weeds in Vidaliaâ sweet onion crops.
Cultivation with a tine weeder and hand weeding are the primary tools currently used for weed control in organic sweet onion (Allium ceps) explained scientist W. Carroll Johnson III.
weeds that emerge during the delay are controlled not effectively by cultivation. Johnson tested herbicides derived from natural products as a way to control these emerged weeds in organic Vidaliaâ sweet onion production.
Johnson said that although these types of herbicide have been studied previously the majority of the studies were performed on warm-season crops and weeds.
Vidaliaâ sweet onion is a dry bulb onion grown in Georgia as a cool-season (winter) crop.
The field experiments showed that weed control was improved not consistently by applying clove oil (10%by volume) with a sprayer calibrated at 50 gallons/acre compared with sprayer calibrated at 25 gallons/acre Johnson said adding that occasional improvements in weed control did not affect onion yield
and that adjuvants provided minimal improvement in weed control from clove oil and did not consistently improve onion yield.
and suggests another disadvantage to using clove oil for weed control in certified organic crop production Johnson noted.
Given the lack of weed response and onion yields to clove oil applied in higher sprayer output volumes
and thistles but less likely to use some common herbaceous flowers. The results are the first evidence that in its new range in the UK the Tree Bumblebee is associated with built-up areas such as towns and villages and that these areas form a large part of its habitat use.
The importance of this adaptation for biological control of problematic weeds in rice fields and the biology of the moth on new host plant have been described in the open access journal Nota Lepidopterologica.
and European yellow-rattle which are weeds commonly present across Europe and Asia. A new study of the populations in northern Iran however has revealed a new host--Sagittaria trifolia commonly known as arrowhead.
Arrowheads are groups of problematic perennial broadleaf weeds that thrive in rice fields and waterways.
The economic importance of this weed has prompted researchers from the Rice Research Institute of Iran to seek for possible solutions for the management of arrowhead.
and seeds of the problematic weed can lead to a dramatic decrease of its germination potential.
#Speckled beetle key to saving crops in Ethiopia, researchers sayan invasive weed poses a serious and frightening threat to farming families in Ethiopia
The weed called parthenium is so destructive that farmers in the east African nation have given despairingly it the nickname faramsissa in Amharic
Farmers have doused the weed in pesticides and ripped it out with their hands but it has only spread further.
Parthenium is native to The americas where a suite of natural enemies that includes the Zygogramma beetle keeps the weed in check.
In the past three decades parthenium has become the second most common weed in Ethiopia suppressing the growth of all other plants
Kamas said those interested in growing olives must keep weeds out of the orchard. What do weeds compete for?
Light nutrients and water he said. Weed control is critical for the establishment of any perennial crop.
Cotton root rot a long-established disease in much of the state has been a problem for young trees according to Stein.
It is shown that far from being serious agricultural weeds all the New zealand Kunzea are important keystone species either forming their own distinct forest types
and fungi--a far cry indeed from their past much undeserved'weed'status. This paper is also a brilliant showcase of how useful is the brand new Phytokeys publishing platform for the advancement of taxonomy.
The finding by Jim Westwood a professor of plant pathology physiology and weed science in the College of Agriculture and Life sciences throws open the door to a new arena of science that explores how plants communicate with each other on a molecular level.
It also gives scientists new insight into ways to fight parasitic weeds that wreak havoc on food crops in some of the poorest parts of the world.
Some of the biofeedstocks currently being examined by the EPA for approval like pennycress have a high risk for invasion Quinn said.
The list was developed using an existing weed risk assessment protocol which includes 49 questions that must be asked about a particular species based on its biology ecology
A cross-disciplinary research team studied the impacts of groundcover management systems and nutrient source on soil characteristics tree health and productivity and insect disease and weed management.
and the growth of weeds including couch grass can be prevented. Paper is also superior to plastics from the viewpoint of plant gas metabolism.
Weedy but Not a Weeds. cordicitum and the varieties that are elevated newly to species belong to section Androceras
The most widespread Androceras species is S. rostratum known as buffalo bur prickly nightshade and Kansas thistle.
While S. cordicitum belongs to a weedy group within the spiny solanums technically it isn't a weed
because weeds are more common and spread easily Bohs says. Like other plants in Androceras the new species and its five-petaled flowers are bilaterally symmetrical (like a mirror image down a vertical line)
Because cover crops can provide weed and erosion control determining the best method for establishing a uniform and dense cover crop stand as soon as possible after planting is a critical first step.
and reduce light penetration to weeds should be a primary focus. Eric Brennan and Jim Leap from the U s. Department of agriculture Agricultural research service (ARS) coauthored the study published in the April 2014 issue of Hortscience.
and weed-suppressive cover crops on beds the authors said. Both drilling and broadcasting methods are used commonly to plant cover crops.
and faster emergence characteristics that would likely increase their ability to suppress weeds that emerge with the cover crop.
When it comes to controlling hay fever-triggering ragweed plants on Detroit vacant lots occasional mowing is worse than no mowing at all
Those are the findings of a new University of Michigan study that surveyed vacant lots in several Detroit neighborhoods for ragweed counting the number of ragweed plants
The researchers found that ragweed was significantly more likely to be present in vacant lots mowed once a year or once every two years--a common practice in Detroit
which ragweed plants thrive. Katz's co-authors on the vegetation study are SNRE's Benjamin Connor Barrie and Tiffany Carey of the U-M Program in the Environment.
The U-M studies found that vacant lots are the main habitat for ragweed in Detroit:
Ragweed densities were six times higher in vacant lots than at locations around occupied homes in the city.
Vacant lots contained up to 42 ragweed plants per square meter. When you consider that the tiny drab flowers of a single ragweed plant can produce up to a billion pollen grains annually it's clear that Detroit vacant lots are pollen factories churning out a noxious product that afflicts thousands of city residents.
The vegetation survey looked at 62 vacant lots in several neighborhoods including Mexicantown Kettering and Core City.
They found that 28 percent of the unmowed lots contained ragweed plants while 63 percent of the annually mowed lots
and 70 percent of the biennially mowed lots contained the weed. Vacant lots mowed at least once a month during the growing season had no ragweed plants.
When these lots are left alone completely other plants rapidly outcompete ragweed Katz said. When the lots are left unmowed the common perennial plants that replace ragweed include goldenrod milkweed Kentucky bluegrass chicory and aster.
When a vacant lot is mowed not for several years the young trees that can encroach include the Norway maple silver maple box elder cottonwood and tree of heaven.
To determine whether ragweed populations are associated with a particular land-use type in Detroit Katz and Carey documented the amount of ragweed found in vacant lots around occupied residences and in city parks.
They also set up pollen collectors at 34 sites and analyzed the concentration of ragweed pollen grains collected at each location.
They found that the amount of ragweed pollen in the air at a collection site was determined both by the abundance of ragweed plants within 10 meters (33 feet) of the collector and by the number of vacant lots within 1 kilometer (0. 62 miles) of the site.
That result drives home the point that pollen is mainly a local and neighborhood-level problem even though public health officials have treated for decades it as a regional problem Katz said.
John Jelesko an associate professor of plant pathology physiology and weed science began studying the plant after experiencing a nasty poison ivy rash himself
Some sites may have been burned more frequently she noted to control weeds. We've got a sneak peek of
The drones also may be deployed in the battle against Palmer amaranth an invasive weed that is spreading across the Midwest
Before the soybean rows close or if we get a different spectrum response from some of these weeds as they break through the canopy we may see some of those weeds show up in the imagery as well to identify where there are hot spots
researchers reportan invasive weed that has put some southern cotton farmers out of business is now finding its way across the Midwest
and grows faster than other weeds and is seed a prolific producer Hager said. It can tolerate drought
As a seedling Palmer amaranth looks a lot like waterhemp another problematic weed that is difficult to control.
and in many areas especially in Georgia it was not uncommon to see cotton fields literally mowed down to prevent this weed from producing seed Hager said.
In 2010 for example Southeast Farm Press reported that the cost of weed control efforts on Georgia farms had risen from $25 per acre to $60 to $100 an acre in response to Palmer amaranth invasions.
--or failing to properly fight--this weed Hager said. If you think about the value of agronomic row crops in this state that's why we're very very concerned about how devastating this could be to us he said.
In about half of those counties the weed is already resistant to glyphosate the most commonly used herbicide on Midwest farms Hager said.
Many farmers think they can use the same techniques that tend to work against other common weeds--a onetime application of glyphosate herbicide for example--to control Palmer amaranth Hager said.
And if the weed gains a foothold in planted fields corn and soybean growers in Illinois should take a tip from Georgia cotton farmers
It's hard to imagine another weed species that would be more injurious to crop production than
which produced tubers but were thought more often of as a weed than a vegetable crop.
New nasty weeds sometimes evolve directly from natural crosses between domesticated species and their wild relatives.
Surely these couldn't be fathers from outside of our wild radish populations--hundreds of meters away?
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