Archive for the ‘Weeds’ Category

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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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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LSU AgCenter weed scientist Daniel Stephenson holds a ragweed parthenium plant Photo by Olivia McClure/LSU AgCenter
LSU AgCenter weed scientist Daniel Stephenson holds a ragweed parthenium plant at the annual field day at the Dean Lee Research and Extension Center in Alexandria on July 13, 2017.

False ragweed becoming major row-crop pest in Louisiana

Ragweed parthenium (also know as false ragweed) has gone from a nuisance in pastures to a major pest in Louisiana row crops.

Bruce Schultz 1, Olivia McClure | Jul 18, 2017

An LSU AgCenter weed scientist speaking at a field day on July 13 at the Dean Lee Research and Extension Center warned farmers about ragweed infestations in their fields.

The scientist, Daniel Stephenson, said ragweed parthenium has gone from a nuisance in pastures to a major pest in Louisiana row crops. Ragweed parthenium is also known as false ragweed.

 The weed can become a major problem quickly if it is not controlled early. Ragweed parthenium often germinates after spring burndown herbicide applications and is not discovered until after crops have emerged, Stephenson said.

Applications of certain herbicides prior to or at planting can provide control of an existing population, he said.

Current research shows that after crop emergence, control options are limited, but Stephenson recommended sequential applications of either Liberty, Liberty plus Roundup PowerMax, or Roundup PowerMax plus a half pound per acre of dicamba.

Stephenson said it’s likely the weed has been spread by equipment.“Ragweed parthenium is a very troublesome weed that is difficult to control with herbicides,” he said. “If a producer sees it in their field, they need to remove it.”

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July 13, 2017

The photo is from https://doi.org/10.1017/wsc.2017.14. It shows one of the plants that come from a population that apparently adapted to taller crops and is GR and another that comes from a population adapted to smaller crops and is GS. Additionally, below you can see a few examples of the great diversity in morphology that we found among Palmer amaranth populations. – Credit: Photo by Ramon Leon

Palmer amaranth is widely considered to be one of the most damaging and difficult to control agricultural weeds in North America. A lot of time and attention has been devoted to herbicide-resistant Palmer amaranth and the significant yield losses it can produce. Research featured in the journal Weed Science, though, shows other “life history” traits may be contributing to crop losses by making Palmer amaranth more aggressive and difficult to control.

Researchers from the University of Florida collected samples of Palmer amaranth from 10 fields in Florida and Georgia. The sites had widely divergent cropping histories – from short-statured vegetables and peanut crops to tall corn and cotton crops. The fields also varied in herbicide use. Some were devoted to organic production, while others had a history of intensive herbicide use.

Significant differences were observed in the traits of the Palmer amaranth from the various fields, such as fresh and dry weight, days to flowering, plant height, leaf shape and canopy. Researchers say these differences could not be explained by whether the Palmer amaranth population was glyphosate resistant or glyphosate susceptible. Instead, crop rotation and crop canopy better explained the many variations found. For example, the tallest populations of Palmer amaranth came from corn fields, while the shortest came from fields planted with the shortest crops.

“It appears Palmer amaranth can evolve life-history traits that increase its potential to grow and reproduce in various cropping systems,” says Ramon Leon, Ph.D., a member of the research team. “To avoid the development of more aggressive weed biotypes, it is important to consider these evolutionary consequences when designing crop rotation systems and weed management strategies.”

Full text of the article “Differentiation of Life-History Traits Among Palmer Amaranth Populations (Amaranthus palmeri) and its Relation to Cropping Systems and Glyphosate Sensitivity” is now available in Weed Science Vol. 65, Issue 3, July-September, 2017.


More news from: Cambridge University


Website: http://www.cam.ac.uk

Published: June 13, 2017

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