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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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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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Southeast Farm Press

  • Soybeans were an effective trap crop, pheromone traps killed stink bugs in the trap crop, and buckwheat plants fed beneficial wasps that reduced stink bug numbers.
Agricultural Research Service

Cotton growers in the United States are concerned about native stink bugs that have attacked cotton and other crops for decades.

The green stink bug (Chinavia hilaris), southern green stink bug (Nezara viridula), and brown stink bug (Euschistus servus) continue to threaten cotton. But an Agricultural Research Service scientist in Georgia has found some environmentally friendly alternatives to insecticides.

“Cotton growers are increasingly interested in producing their crops in ways that have less impact on the environment,” says ARS entomologist Patricia Glynn Tillman, who is based in Tifton, Georgia.

The three native stink bugs are immune to the insect-killing toxins incorporated into most modern cotton varieties. Insecticides are effective, but they also kill the stink bug’s natural enemies, and they often require repeated use throughout the growing season. Organic growers can’t use conventional insecticides.

Stink bugs continue to pose a serious economic threat. Last year, they collectively infested roughly a million acres of cotton in Georgia alone, and growers there spent $12 million to control them. The bugs are a particular problem in the southeastern United States, where cotton is often grown alongside peanuts. Brown and southern green stink bugs develop in peanut fields and migrate into cotton. Green stink bugs move into cotton from nearby wooded areas.

Because of work by Tillman and others, some growers are planting “trap crops,” such as soybean and grain sorghum, to lure stink bugs away from cotton. Other options include pheromone-baited traps, which capture and kill stink bugs, and nectar-producing plants, such as milkweed and buckwheat, to feed native parasitoid wasps that attack stink bugs.

In previous work, Tillman showed the effectiveness of setting up plastic barriers between the cotton and peanut rows. Her recent study focused on whether combining a trap crop, a nectar-producing plant, and pheromone traps would control stink bugs where cotton and peanuts grow.

Tillman and her colleagues grew cotton and peanuts side by side for 2 years. In the first year, they planted soybeans as a trap crop (with and without pheromone traps), between the cotton and peanut plots. In other areas, they placed 6-foot-high plastic barriers between the plots.

In the second year of the study, they added nectar-producing buckwheat plants near the cotton. Each week of the May-to-October growing season, they counted stink bugs and stink bug eggs killed by wasps, and they documented damage to cotton bolls.

They found that the plastic barriers between peanut and cotton were the most effective tool, but the multipronged approach is an effective alternative if barriers are not feasible. Soybeans were an effective trap crop, pheromone traps killed stink bugs in the trap crop, and buckwheat plants fed beneficial wasps that reduced stink bug numbers.

“Protecting Cotton From Stink Bugs” was published in the July 2016 issue of AgResearch Magazine.

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ipm_in_8_principle_s_large

IPM in (8) principle(s)

August 05, 2015

An ENDURE team of 17 co-authors has just published a review paper on the European Union’s eight principles of Integrated Pest Management (IPM). The paper provides researchers, advisers and farmers with an approach for applying these legal requirements intelligently to promote local innovation while reducing reliance on pesticides and associated risks. The authors hope that interest in this approach may help garner support from European and national policy makers to set incentives promoting IPM extension work, demonstrations, research and implementation.

Rather than searching for a universally applicable silver-bullet solution, the authors argue in favour of a broad approach that takes local specificities into account and allows all farmers to engage in IPM at any point within the continuum. Their vision stems from the realistic acceptance that pesticide-based crop protection is simple and efficient in generating spectacular short-term results. More sustainable alternative strategies will inevitably be more complex and knowledge-intensive in their initial development stage.

The process envisioned therefore requires learning, adaptation, and tweaking of a number of farm management practices. It requires extending the challenge of crop protection to larger spatial and temporal scales, and generating more complex cropping systems better adapted to the local context. It also requires attention to non-technical aspects such as the social environment in which farmers operate, collective learning and farmers’ inclination for step-wise rather than drastic changes.

But the approach is viable, and the authors offer real-life examples of successful experiences with the types of tactics and strategies suggested.

The authors note that 70 years of reliance on chemical protection has led to the development of cropping systems that have become inherently vulnerable to pests. By emphasising Principle 1 on prevention, the authors offer concrete illustrations on how to modify cropping systems to make them more robust in the absence of pesticides. The authors also identify the limits and opportunities associated with Principles 2 to 7 – a logical sequence starting with observation and ending with using chemicals as a last resort. Last but not least, a new slant is given on the question of evaluation (Principle 8) regarding the need for the development of new performance criteria and their routine use among the farming community.

For more information:

Barzman M, Bàrberi P, Birch ANE, Boonekamp P, Dachbrodt-Saaydeh S, Graf B, Hommel B, Jensen JE, Kiss J, Kudsk P, Lamichhane JR, Messéan A, Moonen AC, Ratnadass A, Ricci P, Sarah JL, Sattin M. 2015. Eight principles of integrated pest management. Agronomy for Sustainable Development , online first. doi 10.1007/s13593-015-0327-9. It is available here

ANNEX III of Framework Directive 2009/128/EC

General principles of Integrated Pest Management. For ease of reference, the authors have added shorthand titles to each principle

Principle 1 – Prevention and suppression The prevention and/or suppression of harmful organisms should be achieved or supported among other options especially by:

  • Crop rotation
  • Use of adequate cultivation techniques (e.g. stale seedbed technique, sowing dates and densities, under-sowing, conservation tillage, pruning and direct sowing)
  • Use, where appropriate, of resistant/tolerant cultivars and standard/certified seed and planting material
  • Use of balanced fertilisation, liming and irrigation/drainage practices
  • Preventing the spreading of harmful organisms by hygiene measures (e.g. by regular cleansing of machinery and equipment)
  • Protection and enhancement of important beneficial organisms, e.g. by adequate plant protection measures or the utilisation of ecological infrastructures inside and outside production sites
Principle 2 – Monitoring Harmful organisms must be monitored by adequate methods and tools, where available. Such adequate tools should include observations in the field as well as scientifically sound warning, forecasting and early diagnosis systems, where feasible, as well as the use of advice from professionally qualified advisers.
Principle 3 – Decision-making Based on the results of the monitoring the professional user has to decide whether and when to apply plant protection measures. Robust and scientifically sound threshold values are essential components for decision-making. For harmful organisms, threshold levels defined for the region, specific areas, crops and particular climatic conditions must be taken into account before treatments, where feasible.
Principle 4 – Non-chemical methods Sustainable biological, physical and other non-chemical methods must be preferred to chemical methods if they provide satisfactory pest control.
Principle 5 – Pesticide selection The pesticides applied shall be as specific as possible for the target and shall have the least side effects on human health, non-target organisms and the environment.
Principle 6 – Reduced pesticide use The professional user should keep the use of pesticides and other forms of intervention to levels that are necessary, e.g. by reduced doses, reduced application frequency or partial applications, considering that the level of risk in vegetation is acceptable and they do not increase the risk for development of resistance in populations of harmful organisms.
Principle 7 – Anti-resistance strategies Where the risk of resistance against a plant protection measure is known and where the level of harmful organisms requires repeated application of pesticides to the crops, available anti-resistance strategies should be applied to maintain the effectiveness of the products. This may include the use of multiple pesticides with different modes of action.
Principle 8 – Evaluation Based on the records on the use of pesticides and on the monitoring of harmful organisms the professional user should check the success of the applied plant protection measures.

 

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Entomology Today

http://entomologytoday.org/2015/06/15/ipm-strategies-to-fight-the-colorado-potato-beetle/

leptinotarsa-decemlineata

Colorado potato beetle (Leptinotarsa decemlineata). Photo by Scott Bauer, USDA Agricultural Research Service, Bugwood.org.

By Harvey Black

As the effectiveness of the primary chemical weapon against the Colorado potato beetle (Leptinotarsa decemlineata) starts to wane, new ways to manage this pest are needed where potatoes are intensively grown, according to an article in the the Journal of Integrated Pest Management.

Harvey Black

The beetle is a major problem in areas such as Wisconsin, Michigan, New York, and Maine. It attacks the foliage of the potato, thus interfering with photosynthesis and reducing energy that helps the potato grow. Both chemical and non-chemical methods can be used to deal with the pest, according to two of the authors — Anders Huseth, a postdoctoral associate at North Carolina State University and Russell Groves, a professor of entomology at the University of Wisconsin-Madison.

Neconicotinoid insecticides have been successfully used since 1995 to fight the beetle, but their effectiveness has been waning in some areas. While resistance is increasing, Huseth notes that it may not spread to all areas where potatoes are grown. Areas where potatoes are not grown year after year on the same soil are less likely to see insecticide-resistant potato beetles.

But to ward off resistance where it may become an issue, the researchers advocate moving away from broad-spectrum pesticides toward more highly targeted ones, as well as using non-chemical methods.

The beetle “has a long and decorated history of developing resistance to most of the chemical classes that have been used against it,” Groves said.

Hence, the researchers have devised a strategy of rotating various pesticides with different modes of action over the years in order to prevent, or at least significantly delay, the development of resistance.

For example, one strategy calls for using benzoylureas — an insect growth regulator that interferes with chitin synthesis — early in the season, followed by a late-season application of spinosyn, which interferes with the nervous system. The second year would begin with an early-season application of diamide, which affects muscle contraction.

The researchers also note that non-chemical, or cultural, means can be effective as well. For example, crop rotation can, in certain cases, be effective.

As Groves explained, the beetles are tired after emerging from under the ground after winter.

“It has used a lot of its energy to simply stay alive,” he said. “The vast majority have only enough energy reserves to walk about one quarter of a mile. If a grower can move the crop up to half a mile from last year’s [planting], it can have a significant effect.”

But that may be hard to do, given the location of farms and the nearby presence of housing, according to Amanda Gevens, assistant professor of plant pathology at the University of Wisconsin-Madison, who was not involved in the research.

One solution, said Groves, is what he calls area-wide pest management, in which various growers cooperate. But, he added, the “impetus to do that has never been great.”

Another non-chemical approach is called the spring trap crop, which is essentially a decoy for the beetle. According to Huseth, a small “trap” crop can be planted two weeks before the main commercial crop is planted.

“The idea is that the foliage is up and expanding before the primary crop emerges,” he said. “When the adults have colonized that trap crop, they are in a confined spot, so the crop can be destroyed with a mechanical method like a soil chopper (a device like a lawnmower) and you’re not using any insecticide, so there is no selection pressure, but you’re managing the adults before they get into the commercial crop, lay eggs, and attack the crop.”

However, Gevens cautions that this method may only be practical for small and moderate scale growers.

“When you move to larger fields that may be 80 acres or greater, fields are more highly concentrated and the trap crops won’t work as well, given the quantity of potato and attractive plant material for the insect pests,” she said.

While non-chemical means of controlling the beetle and other pests may be helpful, pesticides “used in a judicious way” will always be a factor in growing potatoes, according to Huseth.

“Pesticides in this system are important,” he said. “Pesticides are commonly used. That’s where growers are as far as their pest-management toolbox. A rapid transition away may not be in their best interests as far a profitable crop. To that end, we wanted to provide alternative recommendations that can help them manage resistance with cultural controls.”

Read more at:

Managing Colorado Potato Beetle Insecticide Resistance: New Tools and Strategies for the Next Decade of Pest Control in Potato


Harvey Black is a freelance science writer. A long-time resident of Madison, Wisconsin, he has written for numerous publications including Environmental Health Perspectives, Scientific American Mind, New Scientist, The Scientist, and the Milwaukee Journal Sentinel.

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FreshPlaza

Publication date: 3/23/2015

eight_col_064_IS09AL1QZFarmer with basket of organic potatoes.

New research shows a plastic mesh cover laid over potato crops could be the answer to fighting potato pests without using chemical sprays.

Scientists at the Future Farming Centre and Lincoln University say field trials of the mesh cover is showing exciting results in controlling the tomato potato psyllid as well as reducing potato blight.

The psyllid arrived in New Zealand in 2006 and can cause severe crop loss through its bacterium.

Researchers Dr Charles Merfield said the trials over two growing seasons in Canterbury showed potatoes under the mesh covers had reduced numbers of psyllids, increased tuber size and an increase in overall yield.

He says the covers were widely used in other countries and he expected them to become popular in New Zealand.

“These mesh crop covers have been in use in Europe for probably nearly two decades now, so they’re very widely used over there for pest control, particularly amongst organic growers, so these strike me as being an ideal way of controlling psyllids on potatoes on field crops.

“We did some initial trials at the Future Farming Centre and we’ve got some very good results in terms of controlling psyllid – and we also got the surprise effect of a dramatic reduction in potato blight as well.”

Dr Merfield said the mesh could also control a wide range of pests on many different field crops and was being used by organic growers in Hawke’s Bay to control root fly on carrots.

Source: radionz.co.nz

http://www.freshplaza.com/article/137097/NZ-Mesh-cover-to-fight-potato-pests?utm_campaign=newsletter&utm_medium=ed5&utm_source=s1

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Times of Oman

OMAN
BY SARAH MACDONALD | DECEMBER 15, 2014 , 9 : 57 PM GST

lime treesThere are some new lime trees planted nearby, but Al Zadjali predicts they will soon be infected, too, and die within a few years. –Photos, videos OK Mohammed Ali

Muscat: Since the 1970s Oman has lost more than one million lime trees to a disease with no known cure, but now a scientist from the Ministry of Agriculture and Fisheries has found a way to grow disease-free trees to rehabilitate the Sultanate’s lime production.

Dr Abdullah Dawood Al Zadjali, a plant pathology researcher, is a leading expert on Witches’ Broom Disease of Lime (WBDL), a disease which has devastated Omani citrus trees since it first emerged in the 1970s. But the tides may be turning for citrus farmers in Oman, as he has found a way to overcome the disease by growing tissue cultures from disease-free blossoms and grafting them onto new disease resistant root stocks.

Walking through a farm in Al Rumais, a few kilometres from his research lab, he looks at some lime trees that are infected by the disease.

“The tree will die completely in four to five years. This part was green before, but if it dies, the limes will die, too,” he says, examining of a lime tree that has some normal branches and others that are dry and leafless, much like the witches’ broomstick the disease was named after.

Al Zadjali, who has a PhD from the Tokyo University of Agriculture and Technology, points to a part of the tree with small, bushy leaves that look similar to flowers, and explains that this is another symptom of WBDL, which is caused by a microorganism bacteria called ‘phytoplasmas.’

The ‘phytoplasmas’ are carried from plant to plant by insects, usually leaf-hoppers. They cause leaf-like structures to grow in place of flowers, yellowing leaves, and dead branches that look like witches’ brooms. The fruits that grow are small. Eventually, the disease causes the tree to die.

The ‘phytoplasmas’ are an obligate parasite, which means they can only survive if they are inside the host plant or the vector, which is the insect that carries the disease from tree to tree. They can’t live in the soil or in the air.

There are some new lime trees planted nearby, but Al Zadjali predicts they will soon be infected, too, and die within a few years. As the trees die off from the disease, new ones are planted. But these, too, soon die as they are in the same area as infected ones and the disease is easily transferred. Many of the new trees live just four to six years before dying.

“Annually, we’re losing a lot of trees. The Ministry is distributing new trees to the farmers but those trees, in two to six years, die, too. Once the farmer sees the tree showing some symptoms he should eradicate the tree, even the roots, so as not to transfer the disease to other trees,” he advises.

One way to control the plant is to control the vector, in this the leaf-hoppers, but Al Zadjali says this is much too difficult. “We found the only way to overcome the disease is to grow clean material, disease-free, and distribute those to the farmers so we can reduce the disease in the environment. Or we can clean the areas of citrus plants and replant the area with 100% certified, clean material, free from diseases,” explains Al Zadjali.

Back in his lab he has thousands of disease-free trees which are growing at different stages. Some are still new tissue cultures growing in test tubes; others are new seedlings measuring a 10 or 20 centimetres, while some are even producing fruit.

The success rate for the technique he and his team uses and is incredibly low, no more than 5%, but slowly they are making progress and now have about 1,500 mother plants from which more trees can be grown.

Mother plant
“We are so proud and so happy we succeeded to get the mother plants and also to find good results in the field where we’re using the resistant root stocks,” he mentions.

Now they are moving on to the mass production of seedlings. By the end of 2015 the aim is 15,000 seedlings, and another 20,000 by the end of 2016.

“The project is aiming to protect disease-free mother plants. Phase two is the mass production of seedlings. We need to produce at least 10,000 seedlings annually. Now we have here more almost 15,000 root stock seedlings,” he says, wandering through a green house which has row after row of young trees.

Not only have Al Zadjali and his assistants managed to grow of Omani limes, they have been successful in growing other varieties of disease-free citrus including oranges, grapefruits, lemons and others fruits from Oman in the past four years, as well as some international varieties.

“We’re very proud because our target was Omani lime, but we’ve succeeded to produce over 15 different varieties,” he comments.

Al Zadjali says it’s important to use Omani specimens for growing clean trees, because they save Oman’s agricultural history and identity that way.

“If we import disease-free plants from other countries it costs us too much money and we will lose our indigenous species,” he says.

Now, Al Zadjali hopes the Ministry of Agriculture will be able to provide farmers with disease-free limes and teach private nurseries how to grow and sell clean trees, too.

His project, which started in 2010 and is funded by the Agriculture and Fisheries Development Fund, aims to produce enough disease-free trees to replenish the lime crops in Oman, bringing the industry back to its former glory days before WBDL appeared in the Sultanate.

“This is the kind of solution that helps us get our lime industry back, and be part of the income for the farmers. Economically it will be important,” he says.

For generations many Omani farmers depended on limes as a major part of their livelihoods. According to Al Zadjali’s research, in 1973, Port Sultan Qaboos alone exported OMR36 million worth of limes. The export of limes was the third largest part of the national income after oil and dates, he says.

“If we have a big number of lime trees we can make not just a fruit industry, but we can produce factories for producing concentrating juices. We can have incense, perfumes, soaps. We can use limes for many purposes, so that will create a lot of job opportunities for Omani people,” he says.

For Al Zadjali, who has been studying WBDL since the early 1990s and make it the subject of both his Master’s degree and PhD, finding a way to tackle the disease and help Omani farmers and national economy has become more than a job. It has become a personal passion and mission.

http://www.timesofoman.com/News/44336/Article-Omani-scientist-battles-%E2%80%98Witches%E2%80%99-Broom%E2%80%99#

To get in touch with the reporter: sarah@timesofoman.com

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