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Rust fungus proving value in battle against lantana

04 October, 2017

Rust fungus proving value in battle against lantana

A rust fungus introduced to New Zealand two years ago to wage biological war against ‘Lantana camara’ is starting to have a noticeable impact on the pest plant in Northland.

Entomologist Jenny Dymock says the Environmental Protection Authority (EPA) approved the release of two rust fungi – Puccinia lantanae andProspodium tuberculatum – to control lantana in April 2012, with both subsequently released in Northland in 2015.

Cable Bay-based Dr Dymock, who works with the Northland Regional Council (NRC), says the fungi were released in the Whangaroa, Doubtless Bay, Awanui and Kohukohu areas in autumn two years ago.

The rusts work by reducing the growth rate and fruit and leaf production of lantana plants, one of the world’s most invasive weeds.

While Puccinia lantanae (a blister rust) did not appear to have established itself in Northland yet, in contrast the leaf rust Prospodium tuberculatum was beginning to have a big impact on local lantana populations, as evidenced by the number of lantana with dead and dying branches.

Lantana is a serious problem in Northland, where it forms dense thickets that invade a wide variety of areas from native and exotic forests to domestic gardens, roadsides, sand dunes, quarries and wasteland.

Typically a low, scrambling shrub with small, colourful flowers, lantana can be poisonous to people and grazing stock. It has thorny stems, strong-smelling leaves, especially if they’re crushed, and produces fruit that’s attractive to birds, which then spread its seeds to uninfested sites.

Dr Dymock says the NRC was behind the original application to the EPA to import the rusts, part of a growing number of host-specific weapons in the council’s biocontrol arsenal.

She says it’s great to see the rust – a native of Brazil – making a noticeable dent in the local lantana population. Surprisingly, in Northland it appears to be damaging lantana especially well during late winter, something Dr Dymock attributes to the wetter conditions.

“Many people will be unaware that we have a range of more than two dozen biological control agents already in use in Northland, with even more likely to be available in the future.”

Biological control is the use of naturally-occurring enemies and diseases to control pests and weeds. A cost-effective and environmentally-friendly method of pest control, it’s not designed to eradicate a species; instead it aims to keep populations at low levels.

Dr Dymock says as well as fungi and bacteria, other biological control tools include an army of insects – including some which target other insects – and even tiny internal parasites.

However, she says the process from lowly insect or fungus to biological control agent is a painstaking, lengthy and initially costly one.

“The NRC typically spends at least $80,000 a year on biological control work and is part of a national group that collectively spends more than $600,000 on this annually.”

She says the first step in finding biocontrol agents is a survey of the natural enemies of the target weed or pest either here in New Zealand and/or overseas.

If no natural enemies of a target weed or pest are found in New Zealand then

potentially suitable overseas candidates from areas with a climate matching Northland’s must be extensively tested in a secure quarantine facility to determine whether they will attack any native New Zealand species or any species that is of economic value.

“Only when researchers are confident the potential biocontrol agent attacks just the target species alone, an application for release from quarantine is made to the EPA, followed by consultation with the public and stakeholders.”

Dr Dymock says it can take years from when an initial hunt for a biological control agent begins to when approval for its release is finally given.

She says those interested in learning more about biocontrol in Northland should visit www.nrc.govt.nz/biologicalcontrol

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Grand Forks, ND




The impact of dicamba drift on fields won’t be known until soybean harvest begins. (Michelle Rook/Special to Agweek)

Yield impact of dicamba injury unknown, label changes possible in SD

HURON, S.D. — The South Dakota Department of Agriculture fielded dozens of dicamba injury complaints from off-target drift this season, and they’re still taking input from farmers to determine the total number of acres hit. State officials are looking at possible label changes for spraying dicamba on Xtend soybeans next year, but a lot of that hinges on what farmers find in the fields this fall.

Farmers that had some or widespread cupping in soybeans this season may not know the full production impact until harvest.

 “The combine will tell, we don’t know,” says Reno Brueggeman, who farms near Miller, S.D. “Nobody knows. It’s one of those things that nobody’s seen before. Maybe nothing is going to come of it, maybe there won’t be any yield loss, but nobody knows.”

South Dakota Secretary of Agriculture Mike Jaspers agrees about the unknowns.

“For the most part I don’t think we’re going to know until harvest gets here,” he says. “Fortunately, we do have the technology of yield monitors and things on the majority of farms, so I think that will help.”

Agronomists are looking at past research on the yield impact of dicamba on soybeans for clues. “The real key was, as long as the growing point wasn’t hurt, it was felt that beans will be fine and recover,” says Paul Johnson, South Dakota State University Extension weed specialist.

 However, he says most of the research was done 40 years ago and the application timing was different then. “The difference is now we are spraying it a month later than we did before, and we really don’t know how those effects will compare the same or not,” Johnson says. “In a lot of cases, maybe we were pushing the window on the application timing, because once we go past the last week of June, we’re going to start flowering and it is just labeled for R1.”


Once more is known on yield impact, then state officials in South Dakota can determine label changes for 2018.

“I think we definitely will see changes in the labeling,” Jaspers says. “In South Dakota we did a one-year, restricted label which will expire in December, so virtually it’s done as the application season is done for this year, so we would have to reassess that label anyway. I’m looking at maybe restricting the time of day to try to get away from those inversion issues, or maybe have a restriction as far as growth stage or calendar date, so we don’t get into the hotter portions of the growing season.”

Jaspers encourages farmers to report damage and yield results to help them with that decision-making process.

“We’re definitely hoping that people will continue to report to the Department of Ag,” he says. “Right on our website there’s a link to a dicamba reporting page.”

Jaspers is also confident they’ll require the product manufacturers to do more education with farmers and applicators before the next growing season.

“In South Dakota we required a lot of education on their part — to come and do a lot of training and education of the applicators. I’m pretty confident that will be one of the key issues right there,” he says.

On the federal level, the Environmental Protection Agency is working with herbicide companies and manufacturers to decide if they will impose other label or application changes.

“I’d be surprised if we won’t see some modifications on the state level,” says Johnson.

The other lingering question is if a farmer proves there was a yield loss, will crop insurance cover that loss? Brueggeman, who is also an agent, says no.

“Crop insurance has to be a natural loss, natural cause of disaster. Your farm liability insurance is going to have to step in on this,” he says.

Despite that, Brueggeman says a large number of farmers are gearing up to plant Xtend soybeans again in 2018 because of the excellent weed control they get, especially on resistant weeds like kochia and waterhemp. He says the technology is not going away.

“There’s a lot of people who are mad and it’s understandable, but I hope they have an open mind. We can get through this point,” he says.

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Cornell Chronicle

Beneficial soil bacteria face a weed-killing threat from above

Blaine Friedlander

Media Contact

Lindsey Hadlock

As farmers battle in their above-ground war on weeds, they may inadvertently create underground casualties – unintentionally attacking the beneficial bacteria that help crops guard against enemy fungus.

Cornell researchers have found an agricultural conflict: negative consequences of the weed-killing herbicide glyphosate on Pseudomonas, a soil-friendly bacteria.

“Beneficial Pseudomonas in the soil can help crops thrive. They can produce plant-stimulating hormones to promote plant growth and antifungals to defeat problematic fungi – such as Pythium and Fusarium – found in agricultural soil, but previous studies reported that the abundance of beneficial bacteria decreased when the herbicide glyphosate seeps underground,” said Ludmilla Aristilde, assistant professor of biological and environmental engineering. “Our study seeks to understand why this happens.”

Soil bacteria require their proteins – composed of amino acids – and their metabolism to support cellular growth and the production of important metabolites to sustain their underground fight. But glyphosate applied to crops can drain into the soil and disrupt the molecular factories in the bacterial cells in some species, interfering with their metabolic and amino acid machinery.

The new findings show that glyphosate does not target the amino acid production and metabolic gadgetry equally among the Pseudomonas species. For example, when Pseudomonas protegens, a bacteria used as a biocontrol agent for cereal crops, and Pseudomonas fluorescens, used as a fungus biocontrol for fruit trees, were exposed to varying glyphosate concentrations, the researchers noted no ill effects. However, in two species of Pseudomonas putida, used in soil fungus control for corn and other crops, the bacteria had notably stunted growth, said Aristilde, who is a faculty fellow at Cornell’s Atkinson Center for a Sustainable Future.

“Thus, if a farmer is using Pseudomonas fluorescens as a biocontrol, then it is probably okay to use glyphosate,” Aristilde said. “But if the farmer uses Pseudomonas putida to control the fungus in the soil, then glyphosate is more likely to prevent the bacteria from doing its job.”

The study offers molecular details for why glyphosate adverse effects on Pseudomonas are species-specific. “That’s actually good news because – as a society – we will likely not stop using herbicide completely,” said Aristilde. “If that is the case, farmers need to know which beneficial soil biocontrol they’re using can be susceptible. If they’re using a strain that is susceptible and conflicting with their herbicide application, then it is a problem. That’s the bottom line.”

Aristilde will present this research to farmers and agricultural professionals Nov. 14 at the Agriculture, Food & Environmental Systems In-Service training hosted in Ithaca by Cornell Cooperative Extension.

Glyphosate-Induced Specific and Widespread Perturbations in the Metabolome of Soil Pseudomonas Species” was published in Frontiers of Environmental Science in June 2017. Co-authors are Michael Reed ’17; graduate student Rebecca Wilkes; Tracy Youngster, M.S. ’17; Matthew Kukurugya, M.S. ’17; Valerie Katz ’18; and Clayton Sasaki ’18. The research was funded by the U.S. Department of Agriculture’s National Institute of Food and Agriculture; the National Science Foundation; and the Academic Venture Fund at Cornell’s Atkinson Center for a Sustainable Future.

Story Contacts

Blaine Friedlander

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KMA land

Monarch migration set to pass through KMAland

Monarch Butterfly
U.S. Fish & Wildlife Service

(Omaha) — As millions of monarch butterflies prepare to migrate through the heart of the United States, scientists remain concerned about the species’ dwindling population.

At their peak, over one billion monarchs made the 3,000-mile trek through KMAland to a forest in Mexico for the winter. As recently as four years ago, the monarch population making that trek had fallen to an estimated 30 million, although that number has rebounded slightly in the last few years. Creighton University Entomologist Dr. Theodore Burk has been studying the butterfly for nearly 20 years. He says it’s truly a unique species.

“The monarch has an absolutely unique biology,” said Burk. “It’s the only species of insect that makes this kind of migration. They’re beautiful; everybody grew up in school raising monarch caterpillars. They are a tremendous poster child.”

  Monarch’s primary food source is milkweed, which typically grows in the Corn Belt. In addition to food, monarchs use milkweed as a place to lay eggs. One of the reasons for a decline in the population has been an increase in pesticide and insecticides that reduce milkweed plants. Burk says education is key to re-establishing milkweed.

“Something over half of all the food base of monarchs has been eliminated just because of this change in American agricultural,” said Burk. “A lot of the efforts that people have been engaged in during the last few years has been to plant more milkweed.”

While on their migration, monarchs also rely on thistle flowers to get them through until Mexico. Burk says some species of thistle are required to be removed by law because they are a noxious weed, further decreasing food for the monarch.

  “Where I study the monarchs on the prairies, I have records of about 1,500 flower visits by monarchs to flowers and more than half of them are to one particular species of tall thistle,” says Burk. “In our part of the world — at least the few hundred miles that they pass through here — that is a really key resource to help get them to Mexico.”

Burk has been studying the butterfly since 1998. He spends 20 weeks each year at Glacier Creek Preserve northwest of Omaha studying and documenting monarchs and their plant preferences


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FTF logo

Large tracts of farmlands and pastures in the Amhara Regional State of Ethiopia are infested by the invasive weed parthenium (Parthenium hysterophorus). Parthenium reduces yields of major crops and replaces valuable pasture species, decreasing livestock productivity. Parthenium also makes many people sick, causing both skin and respiratory allergies, and displaces native plant species, damaging the region’s biodiversity.

In order to combat this weed, a project led by Virginia State University and funded by USAID through the Integrated Pest Management Innovation Lab at Virginia Tech has released two bioagents, the leaf-feeding beetle (Zygogramma bicolorata) and stem-boring weevil (Listronotus setosipennis). On June 20, 2017, thousands of adult Zygogramma and hundreds of Listronotus were released at several parthenium-infested sites around the town of Finote Selam.

 Parthenium at the time of Listronotus release on June 20 2017_

Parthenium at time of Listronotus release, June 20, 2017


 Parthenium at 2 the time of Zygogramma release on June 20 2017

 Parthenium at time of Zygogramma release, June 20, 2017

By mid-August 2017, the bioagents were thriving and damaging parthenium. The Zygogramma kills parthenium by defoliating its leaves while Listronotus inflicts damage to the weed from inside by burrowing its stem. Native vegetation is starting to make a comeback as parthenium is weakened.

Parthenium on August 13 2017 after it was defoliated by Zygogramma. The native vegetation started to recover soon after parthenium was weakend by Zygogramma_

Parthenium on August 13, 2017 after being defoliated by Zygogramma. The mature vegetation soon started to recover after parthenium was defoliated by Zygogramma

 Parthenium on August 13 2017 after it was killed by Listronotus. Other broadleaf plants started to thrive once parthenium was severely damaged by Listronotus_

 Parthenium on August 13, 2017after it was killed by Listronotus. Other broadleaved plants started to thrive once parthenium was severely damaged by Listronotus      

 Zygogramma has also moved from the release site to nearby parthenium-infested fields and started to feed on the weed. Listronotus also started to damage nearby parthenium plants once it finished damaging the ones it was released on. At the new sites, staff observed larvae and newly emerged adults of Zygogramma, indicating that the bioagent is reproducing and new generations are acting against the invasive weed.

The effect of Zygogramma on parthenium as seen at Finote Selam (altitude 6000 ft) is similar to what was observed in Wollenchiti (altitude 4700 ft) after the release of this bioagent in 2016. In Wollenchiti, Zygogramma fed on parthenium on the spot it was released near a railway track and then moved to nearby bean and teff fields that were infested by the weed. Zygogramma defoliated parthenium without touching bean and teff, showing it only attacks the weed and it is safe to other plants. Biological control of parthenium using these two bioagents and others have been successful in reducing the damage caused by this weed in Australia and India.

However, this is just the beginning of the effort to manage parthenium using natural enemies in Amhara and other regions of Ethiopia where this weed is inflicting damage to food crops and livestock. It will require releasing large number of adults of the bioagents at multiple sites in different parts of the country over several years to reach the level of control achieved in Australia and India. It is unlikely that the bioagents will establish from one or two years of release because of predation by birds, ants, and other general feeders. Their numbers will also be negatively affected by extended dry season due to drought and other unfavorable weather conditions.

The time it takes for the bioagents to establish at a particular locality also affects how long the initial release spot remains undisturbed from ploughing and slashing of the parthenium. The bioagents need sites where they can remain undisturbed as adults in the soil during the dry season. They can only self-perpetuate from season to season if they can remain untouched in the soil, especially during the first few years immediately after release. This biocontrol program will require patience and effort over several years to be successful, but the potential for sustained control of parthenium in Ethiopia is very promising.

Wondi Mersie, Ph.D.

Associate Dean and Director of Research

Agricultural Research

Box 9061

Virginia State University

Petersburg, VA 23806


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Farming Online



New study looks at tilling for effective weed management

25 Jul 2017
Categories: Arable

With herbicide resistance on the rise, there is a renewed emphasis on soil tillage as a critical component of integrated weed management.

Although tillage is the subject of an ongoing debate – with studies released this month by NASA and the European Conservation Agriculture Federation emphasising the role minimising soil disturbance and building up soil carbon can play in reducing greenhouse gas emissions from farming – a newly published paper by researchers from the U.S. has backed tillage as a major means of suppressing weeds. The study stresses that, when it comes to weeds, timing matters and when tillage occurs can significantly impact both weed density and the composition of the weed community that emerges from seeds in the soil.

The paper, published in the journal Weed Science, looks at the impact of tillage on four sites in the northeastern U.S. that were tilled every two weeks during the growing season. Six weeks after each tillage cycle, researchers sampled random plots – 196 in total – to measure the density and species of weed seedlings.

They found that total weed density tended to be greatest when soil was tilled early in the growing season. In fact, more than 50 percent fewer weeds emerged after late-season tillage than after early-season tillage.

The composition of the weed communities in the test fields was also impacted by tillage timing. After early-season tillage there was greater unevenness among various weed species, with some species clearly dominating. After late-season tillage, the distribution among weed species tended to be much more even.

“Our results suggest that farmers may be able to better manage weed communities and to mitigate the impact of weeds on crop yields by adjusting the timing of their tillage, crop rotation and other cultural management practices,” says Matthew Ryan of Cornell University, a member of the research team.

Full text of the article can be read here.

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Plantwise Blog

Five invasive pests cost African economy $1 billion every year

New research by CABI reveals that just five invasive alien species are causing US$0.9 – 1.1 billion in economic losses to smallholder farmers across six eastern African countries each year, equating to 1.8% – 2.2% of total agricultural GDP for the region. These losses are expected to grow to $1.0 – 1.2 billion per year over the next 5-10 years, highlighting the urgent need for coordinated responses at regional, national and international levels.

New research published in the open-access journal Global Food Security estimates the alarming level of economic losses suffered by smallholder farmers each year in eastern Africa, to a handful of species that have become damaging crop pests since their introduction to the region. These few invasive species can have devastating impacts on important staples such as maize, but also high-value crops including tomatoes, peas and green beans.

CABI researchers carried out the study to quantify the impacts of five important invasive alien species on mixed maize farming in economic terms. The countries included in the study were Ethiopia, Kenya, Malawi, Rwanda, Tanzania and Uganda, all of which have large rural communities dependent on small-scale farming for food security and income.

Invasive alien species can have a variety of effects on farming, livestock, pastures and forests, as well as human and animal health. Accelerating global trade is increasing the rate of invasive species introduction and establishment, with developing regions some of the worst affected.

CABI invasive species expert, Dr Sean Murphy, said, “Invasive species can have a devastating impact on smallholder livelihoods, and poorly regulated trade and movement of produce can contribute to the spread and establishment of pest species. Invasive species are a growing threat to food security in Africa and the results of this study highlight the need to take action. We urgently require a coordinated response at regional, national and international levels.”

Five important invasive species

The study reports that maize, the most important staple crop in eastern Africa, is affected by several invasive species:

1.As much as $450 million is lost to smallholders each year to the spotted stem borer, Chilo partellus, a caterpillar which feeds inside the growing maize plant, reducing its yield. This pest also attacks other important crops such as sorghum. A biological control agent (Cotesia flavipes) released against this pest is playing an important role in reducing the crop losses suffered by smallholder farmers.

2. Maize Lethal Necrosis Disease (MLND) is caused by a dual viral infection and leads to the production of deformed maize ears which can result in total crop loss. Current smallholder losses to this disease are estimated to be up to $339.3 million each year, but are likely to increase significantly with the ongoing spread of the disease.

3.The invasive ‘famine weed’, Parthenium hysterophorus, affects farmland and pasture, reducing production levels in a variety of crops and having human and animal health impacts. The weed is most widespread in Ethiopia, but is increasing its range in Kenya, Tanzania and Uganda. Current smallholder losses in maize for the region are estimated to be as high as $81.9 million annually, but can be expected to rise with the ongoing march of this damaging weed.

4. Horticultural crops, often grown along with staples such as maize are valuable nutritionally, but also as cash crops that can be an important route out of poverty for smallholder growers. A number of invasive species affect horticultural crops and this study included three species of Liriomyza leaf-mining flies, which attack a variety of important crop families including ornamental plant species and vegetables. In this study, impacts on beans and peas were considered, with total annual losses up to $149.1 million. Climate change is likely to result in a range increase for damaging Liriomyza species.

5. The South American tomato leaf miner, Tuta absoluta, has had a devastating impact since its recent introduction to Africa, frequently causing total crop loss and leading to three-fold increases in tomato prices. Losses to eastern African smallholders are estimated at up to $79.4 million per year at present, but this figure is expected to grow substantially with the rapid spread of this pest.

Taking action

The CABI study clearly highlights the need to improve the outlook for smallholders in developing countries, who are resource-poor and susceptible to invasive species impacts.

Collaboration at national, regional and international levels, analysis of invasion pathways, and implementation of effective monitoring and rapid management responses to new invasive species arrivals are priority areas for follow-up to the study. Where invasive species are widespread, integrated approaches, including biological control, should be considered.

Dr Sean Murphy said, “In carrying out this research, CABI has taken the first step in highlighting the vast scale of losses being suffered by resource-poor smallholders to invasive alien species. This data illustrates that the issue is both critical and pressing. With such a large scale of economic losses to just five invasive species across six countries alone, we need to consider the big picture: a long-term invasive species management policy in Africa with full policy support is needed urgently.”

The recent invasion of Fall armyworm (Spodoptera frugiperda) will add significantly to these losses as it is known to cause great damage to maize and other crops in its native range.

CABI’s global invasive species programme aims to improve the livelihoods of the 50 million poor rural households that are impacted by damaging invasive species. The programme will contribute to improved food security and trade, and will aid the protection of agricultural and natural ecosystems. See the website http://www.invasive-species.org/.


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