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Successful Farming

MARCH OF THE ARMYWORMS

ENTOMOLOGIST TO WINTER WHEAT FARMERS: WAIT TO PLANT.By Bill Spiegel9/21/2021

Armyworm on soybean pods

Kansas State University

An entomologist at Kansas State University urges winter wheat farmers to hold off on planting the crop due to an unusual infestation of fall armyworm that can quickly wipe out lush green wheat.

Jeff Whitworth, Extension agronomist at KSU, says farmers in Kansas are seeding winter wheat now, or will begin soon. With fall armyworm populations thriving, young wheat plants could be eradicated as soon as they emerge, he says.

“I would delay wheat planting as long as possible,” Whitworth says. “If there is any green wheat, these worms have the potential to do a great deal of damage.”

Delaying wheat planting is advised because insecticide seed treatments do not work on armyworms, Whitworth says. “We have tested this several times and they simply don’t work,” he emphasizes. Therefore, growers have two options to prevent damage. One, delay planting until after the Hessian fly-free date. Option two is to plant wheat as planned and monitor for damage. When the threshold gets to five or six armyworms per square foot, spray an insecticide over the top of the wheat crop. Insecticide options include products with active ingredients including pyrethroids, alpha-cypermethrin, beta-cyfluthrin, cyfluthrin, gamma-cyhalothrin, lambda-cyhalothrin, permethrin and zeta cypermethrin, organophosphates, choloropyrifos and carbamates, carbaryl and methomyl.PAID CONTENThttps://api.sele.co/iframe/v4.html?id=3903e723-938c-49bc-878a-55414ad7721d&_sm_xdm=true&use_xdm=1&autoStart=true&auto_start=1&start_muted=true&start_paused=1&disable_tab=1#https://www.agriculture.com/march-of-the-armyworms

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For the latter option, “…there are insecticides that work for armyworms, but is it worth the cost when growers could just delay planting?” Whitworth says.

There are two types of armyworms:

  • Fall armyworms feed on a wide range of host plants, including soybeans, sorghum, alfalfa, and corn. They have four spots on the top of the last abdominal segment, forming a square. They do not overwinter in most High Plains states.
  • True armyworms feed mostly on grasses. They don’t have have the spots fall armyworms possess.

Both species will feed on any plant material if they are hungry enough; they also have the same life cycle.

“Armyworms may continue to cycle through another generation, or even two, as they overwinter in Kansas,” Whitworth says. “Ultimately it will probably take a hard frost or freeze to stop them.”

Bob Wright, Extension entomologist at UNL, agrees. “Given the populations of fall armyworms to the south of us, it is likely moths will continue to be present in southern Nebraska for a while. Fall armyworms have a broad host range and can feed on broadleaf and grassy crops. Be sure to get out and monitor newly seeded alfalfa and wheat as seedling plants can be killed rapidly by caterpillars feeding on them,” Wright says.

WHY NOW?

The 2021 armyworm infestations have been particularly brutal. From Texas north to Nebraska and as far east as Michigan, insects have marched through farm fields, chewing through tender growth of plants and leaving fields bare in their wake.

Armyworms infest primarily grasses (sorghum, corn, brome pastures, lawns, etc.) and often this time of year, wheat, but occasionally alfalfa. Thus, if armyworms are the problem, they could be around through another generation or maybe even two depending upon the weather. If armyworms are relatively small they will probably feed for another 10 to 14 days, then pupate (stop feeding). If they are relatively large, however, they will probably pupate in the next three to seven days. There will probably be at least one more generation of armyworms.

“Hopefully, they will be heading south after these larvae finish feeding and become moths,” Whitworth says.

Also, in the next 30 to 60 days, army cutworm moths should have returned from their summer Rocky Mountain retreat to deposit eggs throughout at least the western two/thirds of the state and thus, these tiny worms will start feeding on wheat and/or alfalfa all winter.Read more about Crops

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OPINION

Protecting Plants Will Protect People and the Planet

ISA Inerpress News Agency

By Barbara WellsReprint |         |  Print | Send by email

ROME, Jul 26 2021 (IPS) – Back-to-back droughts followed by plagues of locusts have pushed over a million people in southern Madagascar to the brink of starvation in recent months. In the worst famine in half a century, villagers have sold their possessions and are eating the locusts, raw cactus fruits, and wild leaves to survive.

Barbara WellsInstead of bringing relief, this year’s rains were accompanied by warm temperatures that created the ideal conditions for infestations of fall armyworm, which destroys mainly maize, one of the main food crops of sub-Saharan Africa.

Drought and famine are not strangers to southern Madagascar, and other areas of eastern Africa, but climate change bringing warmer temperatures is believed to be exacerbating this latest tragedy, according to The Deep South, a new report by the World Bank.

Up to 40% of global food output is lost each year through pests and diseases, according to FAO estimates, while up to 811 million people suffer from hunger. Climate change is one of several factors driving this threat, while trade and travel transport plant pests and pathogens around the world, and environmental degradation facilitates their establishment.

Crop pests and pathogens have threatened food supplies since agriculture began. The Irish potato famine of the late 1840s, caused by late blight disease, killed about one million people. The ancient Greeks and Romans were well familiar with wheat stem rust, which continues to destroy harvests in developing countries.

But recent research on the impact of temperature increases in the tropics caused by climate change has documented an expansion of some crop pests and diseases into more northern and southern latitudes at an average of about 2.7 km a year.

Prevention is critical to confronting such threats, as brutally demonstrated by the impact of the COVID-19 pandemic on humankind. It is far more cost-effective to protect plants from pests and diseases rather than tackling full-blown emergencies.

One way to protect food production is with pest- and disease-resistant crop varieties, meaning that the conservation, sharing, and use of crop biodiversity to breed resistant varieties is a key component of the global battle for food security.

CGIAR manages a network of publicly-held gene banks around the world that safeguard and share crop biodiversity and facilitate its use in breeding more resistant, climate-resilient and productive varieties. It is essential that this exchange doesn’t exacerbate the problem, so CGIAR works with international and national plant health authorities to ensure that material distributed is free of pests and pathogens, following the highest standards and protocols for sharing plant germplasm. The distribution and use of that germplasm for crop improvement is essential for cutting the estimated 540 billion US dollars of losses due to plant diseases annually.

Understanding the relationship between climate change and plant health is key to conserving biodiversity and boosting food production today and for future generations. Human-driven climate change is the challenge of our time. It poses grave threats to agriculture and is already affecting the food security and incomes of small-scale farming households across the developing world.

We need to improve the tools and innovations available to farmers. Rice production is both a driver and victim of climate change. Extreme weather events menace the livelihoods of 144 million smallholder rice farmers. Yet traditional cultivation methods such as flooded paddies contribute approximately 10% of global man-made methane, a potent greenhouse gas. By leveraging rice genetic diversity and improving cultivation techniques we can reduce greenhouse gas emissions, enhance efficiency, and help farmers adapt to future climates.

We also need to be cognizant that gender relationships matter in crop management. A lack of gender perspectives has hindered wider adoption of resistant varieties and practices such as integrated pest management. Collaboration between social and crop scientists to co-design inclusive innovations is essential.

Men and women often value different aspects of crops and technologies. Men may value high yielding disease-resistant varieties, whereas women prioritize traits related to food security, such as early maturity. Incorporating women’s preferences into a new variety is a question of gender equity and economic necessity. Women produce a significant proportion of the food grown globally. If they had the same access to productive resources as men, such as improved varieties, women could increase yields by 20-30%, which would generate up to a 4% increase in the total agricultural output of developing countries.

Practices to grow healthy crops also need to include environmental considerations. What is known as a One Health Approach starts from the recognition that life is not segmented. All is connected. Rooted in concerns over threats of zoonotic diseases spreading from animals, especially livestock, to humans, the concept has been broadened to encompass agriculture and the environment.

This ecosystem approach combines different strategies and practices, such as minimizing pesticide use. This helps protect pollinators, animals that eat crop pests, and other beneficial organisms.

The challenge is to produce enough food to feed a growing population without increasing agriculture’s negative impacts on the environment, particularly through greenhouse gas emissions and unsustainable farming practices that degrade vital soil and water resources, and threaten biodiversity.

Behavioral and policy change on the part of farmers, consumers, and governments will be just as important as technological innovation to achieve this.

The goal of zero hunger is unattainable without the vibrancy of healthy plants, the source of the food we eat and the air we breathe. The quest for a food secure future, enshrined in the UN Sustainable Development Goals, requires us to combine research and development with local and international cooperation so that efforts led by CGIAR to protect plant health, and increase agriculture’s benefits, reach the communities most in need.

Barbara H. Wells MSc, PhD is the Global Director of Genetic Innovation at the CGIAR and Director General of the International Potato Center. She has worked in senior-executive level in the agricultural and forestry sectors for over 30 years.https://platform.twitter.com/widgets/follow_button.f88235f49a156f8b4cab34c7bc1a0acc.en.html#dnt=false&id=twitter-widget-0&lang=en&screen_name=IPSNewsUNBureau&show_count=false&show_screen_name=true&size=l&time=1629524871809

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Fall armyworms eating rice leaves in a flooded field. Entomologists seek emergency-use exemption to help rice growers in ‘epic’ battle against armyworms.

Mary Hightower, U of A System Division of Agriculture | Jul 22, 2021SUGGESTED EVENT

Events Page - Farm Progress Show 2021

Farm Progress ShowAug 31, 2021 to Sep 02, 2021

University of Arkansas System Division of Agriculture entomologists are seeking an emergency exemption to allow for the use of Intrepid to help control armyworms that threaten the state’s 1.24 million acres of rice. 

“This is the biggest outbreak of fall armyworm situation that I’ve ever seen in my career,” Gus Lorenz, extension entomologist for the Division of Agriculture, said Wednesday. “They’re in pastures, rice, soybeans, grain sorghum. It’s epic.”https://d4100051ff2b64e2ac90e81feaf8c9c5.safeframe.googlesyndication.com/safeframe/1-0-38/html/container.html

Lorenz said the Section 18 request to enable use of Intrepid should be submitted to the Arkansas State Plant Board by Friday.

Intrepid is a growth regulator that’s approved for use in just about every other row crop but is not labeled for use in rice.

“This armyworm thing started about three to four weeks ago,” he said. “It’s continued to build from that time. It’s from the Boot heel of Missouri down to Louisiana.”

Eaten to the ground

Gus Lorenz51326207237_6519faedbd_o.png

Sweep net full of armyworms. Taken July 21, 2021.Lorenz said he received a call from a producer in “south Arkansas, that they’d eaten his bermudagrass pasture to the ground. It was a 30- to 40-acre pasture. And he wasn’t even calling about the pasture. He was calling about his rice crop. He said his rice was being eaten to the ground.”

“Fall armyworm is a particularly voracious caterpillar,” said Jarrod Hardke, extension rice agronomist for the Division of Agriculture. “They have a tendency to surprise us because adults lay very large egg masses but the earliest instar larvae eat very little. It’s not until they get older and start to spread out that they consume most of the food in their life cycle.

“This is why we go from zero to TREAT seemingly overnight,” Hardke said.

Why a Section 18?

51327145063_f633537f6a_o.jpgExtension entomologist Nick Bateman examines a rice field in Jefferson County on July 21, 2021 for fall armyworms. (U of A System Kurt Beaty)

Typically, armyworms can be managed well using pyrethroids, but Lorenz said “when this outbreak first started, we got reports out of Texas and Louisiana that they weren’t getting control. We’re getting failures.”

Lorenz said he and colleagues ran some quick tests, spraying this year’s armyworms with pyrethroids “and we got 48% control.”

In cattle-heavy parts of the state producers use another insect growth regulator called Dimilin to manage armyworms, but in row crop country, “they just don’t carry it. It’s just not available,” Lorenz said.

Fellow extension entomologist Nick Bateman said, “another problem with using Dimilin is the pre-harvest interval. The pre-harvest interval on Dimilin is 80 days which will lead to major harvest issues.”

“We’re limited on the options in control for rice,” he said. “It’s not just a problem of row rice. We are also seeing them in flooded rice, all through the field. They are eating rice all the way down to the waterline.”

Lorenz said rice growers in California sought and received a Section 18 exemptions over the last three years. “We felt like that was our best option.”

Arkansas farmers who managed to replant after the floods and heavy rain in June have young, tender plants that are highly attractive to armyworms.

“Those crops are extremely susceptible to damage from armyworms,” Lorenz said.

What’s next

“My concern is that if we get another generation of them, the next wave could be unbelievable,” he said.

The first generation of armyworms matured into moths in Texas and Louisiana and flew northward. Now that they’re in Arkansas, “We’re making our own generation, which is what makes it so dangerous,” Lorenz said.

There’s also a chance that, depending on the environment, “the population could collapse,” he said. “There are some natural controls out there. When you get a big buildup a lot of things can happen. There are a lot of naturally occurring pathogens that can help control them.”

Some agents in southwest Arkansas found armyworms that had fallen victim to a naturally occurring virus. Lorenz is hoping that virus may provide another option for control in the future.

Arkansas is the nation’s leading rice producer. 

Use of product names does not imply endorsement.Source: University of Arkansas System Division of Agriculture, which is solely responsible for the information provided and is wholly owned by the source. Informa Business Media and all its subsidiaries are not responsible for any of the content contained in this information asset.

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NEWS RELEASE 21-JUN-2021

Butterflies cross the Sahara in longest-known insect migration

EurekAlert!

Weather conditions shown to have big influence on migration numbers

UNIVERSITY OF READING

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IMAGE: A PAINTED LADY BUTTERFLY IN MOROCCO view more CREDIT: ORIO MASSANA

A species of butterfly found in Sub-Saharan Africa is able to migrate thousands of miles to Europe, crossing the Saharan Desert, in years when weather conditions are favourable, scientists have found.

The striking Painted Lady (Vanessa cardui) butterfly has been shown for the first time to be capable of making the 12,000-14,000km round trip – the longest insect migration known so far – in greater numbers, when wetter conditions in the desert help the plants on which it lays eggs.

The international research team’s findings increase understanding of how insects, including pollinators, pests and the diseases they carry could spread between continents in future as climate change alters seasonal conditions.

Professor Tom Oliver, an ecologist at the University of Reading and co-author of the study, said: “We know that the number of Painted Lady butterflies in Europe varies wildly, sometimes with 100 times more from one year to the next. However, the conditions that caused this were unknown, and the suggestion the butterflies could cross the Sahara desert and oceans to reach Europe was not proven.

“This research shows this unlikely journey is possible, and that certain climate conditions leading up to migration season have a big influence on the numbers that make it. It demonstrates how the wildlife we see in the UK can transcend national boundaries, and protecting such species requires strong international cooperation”.

As well as answering long-asked questions about butterfly migrations, the findings could help predictions of the movements of other insects that affect people, such as the locusts currently plaguing East Africa, or by malaria-carrying mosquitoes.

Professor Oliver said: “We enjoy seeing the beautiful Painted Lady butterflies in our gardens in Europe, but climate change will also lead to shifts in invasive species that are crop pests or those that spread diseases. Food shortages in East Africa are a reminder that the impacts of climate change can be much more dramatic than a few degrees of warming might first seem.”

The Painted Lady migrates during the spring, following a winter breeding season. Researchers used long-term monitoring data from thousands of trained volunteer recorders, along with climate and atmospheric data in regions of Sub-Saharan Africa and Europe to learn about their movement.

The study, published in the Proceedings of the National Academy of Sciences journal, found that increased vegetation in the African Savanna during the winter and in North Africa in the spring, combined with favourable tail winds, are the three most important factors in the number that migrate to Europe.

Painted Lady caterpillars feed on the leaves of plants that thrive in wetter winter conditions in the Savannah and Sahel regions of sub-Saharan Africa, causing population numbers to explode. They migrate across the Sahara, and when there are also wet and green spring conditions in North Africa these allow further breeding and swell the numbers that cross the Mediterranean Sea to reach Europe.

Simulations by the scientists also showed that there are regularly favourable tailwinds between Africa and Western Europe, offering insects opportunities for transcontinental travel.

The team calculated that the butterflies must fly non-stop during the day and rest during night to cross the Sahara, making stops to feed on nectar. This is similar to the pattern in which night-flying songbirds migrate.

They concluded the butterflies must fly up to 1-3km above sea level to take advantage of favourable tailwinds, as their maximum self-powered flying speed of around 6 metres per second would make a Sahara crossing extremely difficult.

The researchers used observations of similar butterfly species to calculate that Painted Ladies have enough body fat after metamorphosis to sustain 40 hours of non-stop flying, and keep this topped up by feeding on nectar whenever possible in order to cross the Sahara.

The findings may help improve predictions of which insect species might be found in different regions in future due to climate change, and the numbers they could arrive in.

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Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.

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Iran’s battle against migratory desert locusts successful

Mehr News Agency

Iran's battle against migratory desert locusts successful

TEHRAN, May 23 (MNA) – Director of the Plant Protection Organization of Iran, has said that the country has successfully repelled two swarms of desert locusts so far through taking necessary measures.

“So far, there have been two attacks by deserts locusts invading the country, which have been repelled and the country’s farms have not been damaged,” the head of the Plant Protection Organization of the I.R. Iran, Keikhosrow Changlvaei, said. 

He added, “Of course, the danger has not been eliminated yet and according to the reports of international organizations, in July and November of this year, the country will be exposed to the swarms of desert locusts again.”

“Desert locusts are originated from Saudi Arabia, the Indian subcontinent, and the Horn of Africa, and from these areas they move towards other countries, including Iran, in order to find suitable food and soil,” said Changlvaei.

The Chairman of the Plant Protection Organization added that these locusts have been fought well in the countries of their origin and the sizes of their dangers have been lowered.

Changlvaei added that Iran has prepared for fighting this pest, underlining that “We are ready in terms of facilities, pesticide, and well-trained personnel.”

He also said that his organization also receives help from the country’s military in the fight against migratory desert locusts.

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New crop-destroying locust swarms hitting East Africa ‘nearly every day,’ UN warns in renewed call to fight major food security threat

United Nations | January 21, 2021

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Credit: AP
Credit: AP

This article or excerpt is included in the GLP’s daily curated selection of ideologically diverse news, opinion and analysis of biotechnology innovation.

Dominique Burgeon, FAO’s [the UN’s Food and Agriculture Organization] Director of Emergencies and Resilience, said the huge [African] desert locust swarms in 2020, some as wide as 60 kilometers, had not been seen in decades, threatening food security in a region where many were already going hungry. 

Surveillance and response led to 1.6 million hectares of land being treated.  As a result, more than three million tonnes of cereals, valued at approximately $940 million, were protected: enough to feed 21 million people for a year. 

“We can say that huge progress has been made, capacities of the countries have been tremendously augmented…but yet the situation is not over”, he told journalists. “We have made a huge effort, we are much better prepared, but we should not be complacent. We should not relax.”  

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With neighboring countries battling crop-ravaging locusts, Zimbabwe readies itself for potential outbreak

Sifelani Tsiko | Zimbabwe Herald | January 22, 2021

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Credit: National Geographic
Credit: National Geographic

This article or excerpt is included in the GLP’s daily curated selection of ideologically diverse news, opinion and analysis of biotechnology innovation.

Shingirai Nyamutukwa, head of the [Zimbabwe] Plant Quarantine and Plant Protection Research Services Institute [January 17] said there was an alert following reports of a new round of locust outbreaks.

“Yes, it’s true that Namibia and Botswana are battling another wave of locust outbreaks. The locusts are in all stages from nymphs to adults. We’re keeping check on their control efforts so as to assess risks of invasion into Zimbabwe,” he said.

Last year, locust outbreaks in Zimbabwe, Botswana, Namibia and Zambia were controlled.

Heavy rains have created conducive conditions for swarms to breed in these countries, forcing plant protection agencies to take steps to control any outbreaks.

SADC and partner organisations like International Red Locust Control Organization for Central and Southern Africa (IRLCO-CSA) were working with the four countries to control the pest and protect people’s livelihoods.Follow the latest news and policy debates on agricultural biotech and biomedicine? Subscribe to our newsletter.SIGN UP

In Namibia and Botswana, the plant protection expert said, some other types of locusts are emerging besides the African migratory locust owing to the wet weather which create favorable factors for all these insects to multiply.

“With a lot of food available due to good rains, we expect the region to have a [difficult time fighting] locust outbreaks throughout the last half of the season,” Nyamutukwa said.

Read the original post 

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East Africa gets ready for return of destructive locust swarms

In 2020, East Africa was struck by the worst locust plague in decades. Unfortunately, now, the swarms are returning.

The locusts invading East Africa last year ravaged crops and pastures and drove the levels of hunger and economic hardship higher in parts of the region. One year later, right at the start of 2021, the United Nations has warned that a second and maybe even deadlier return of locusts has already begun.

The first wave of the pests emerged at the end of 2019, numbering in hundreds of billions, multiplying by a factor of 20 per generation, according to the UN Food and Agriculture Organization (FAO). The second generation in March and April numbered in the trillions. A plague that spread like wildfire — up to now.

Image: FAO / DUS

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“It’s a continuation of the 2020 locusts swarm. The adults have flown to various areas and are laying eggs”, Frances Duncan, Professor of Animal, Plant & Environmental Sciences at the University of the Witwatersrand, told DW. “If we have good rains like it is the case at the moment in most areas, the hoppers will hatch, and we get the second wave of the swarm.”

However, Keith Cressman, FAO’s Senior Locust Forecasting Officer, remains optimistic. “I think it’s still a very dangerous situation. But it should not be worse as it was last year.” According to the weather forecast, the months to come should be dry, reducing the locusts’ reproductive rate.

Publication date: Wed 6 Jan 2021

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The Economist

A plague of insects
Why locusts swarm

A new discovery could offer novel ways of controlling the insectsScience & technologyAug 15th 2020 edition


Aug 15th 2020

  • In some parts of the world, covid-19 is not the only plague that 2020 has brought. In parts of Asia and east Africa, swarms of locusts have stripped fields. The un reckons the swarms in India and Pakistan are the largest for a quarter of a century, and that the numbers in Kenya are the highest for 70 years. One swarm in northern Kenya was estimated to be 25 miles (40km) long and 37 miles wide.

Locusts are usually inoffensive, solitary creatures that do not stray far from the place that they were born. But under the right circumstances—namely heavy rain, and a subsequent boom in plant growth—they can become “gregarious”. When that happens the insects change colour and gather in ravenous swarms which can fly more than 100km in a day.

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Rising carbon dioxide levels pose a previously

July 10, 2018, University of Michigan
Researcher Leslie Decker with a monarch butterfly in a University of Michigan laboratory. Credit: Austin Thomason/Michigan Photography

A new study conducted at the University of Michigan reveals a previously unrecognized threat to monarch butterflies: Mounting levels of atmospheric carbon dioxide reduce the medicinal properties of milkweed plant that protect the iconic insects from disease.

Milkweed leaves contain bitter toxins that help monarchs ward off predators and parasites, and the plant is the sole food of . In a multi-year experiment at the U-M Biological Station, researchers grew four milkweed species with varying levels of those protective compounds, which are called cardenolides.

Half the were grown under normal carbon dioxide levels, and half of them were bathed, from dawn to dusk, in nearly twice that amount. Then the plants were fed to hundreds of monarch caterpillars.

The study showed that the most protective of the four milkweed species lost its medicinal properties when grown under elevated CO2, resulting in a steep decline in the monarch’s ability to tolerate a common parasite, as well as a lifespan reduction of one week.

The study looked solely at how elevated carbon dioxide levels alter plant chemistry and how those changes, in turn, affect interactions between monarchs and their parasites. It did not examine the climate-altering effects of the heat-trapping gas emitted when fossil fuels are burned.

“We discovered a previously unrecognized, indirect mechanism by which ongoing environmental change—in this case, rising levels of atmospheric CO2—can act on disease in monarch butterflies,” said Leslie Decker, first author of the study, which is scheduled for publication July 10 in the journal Ecology Letters.

“Our results emphasize that global environmental change may influence parasite-host interactions through changes in the medicinal properties of plants,” said Decker, who conducted the research for her doctoral dissertation in the U-M Department of Ecology and Evolutionary Biology. She is now a postdoctoral researcher at Stanford University.

U-M ecologist Mark Hunter, Decker’s dissertation adviser and co-author of the Ecology Letters paper, said findings of the monarch study have broad implications. Many animals, including humans, use chemicals in the environment to help them control parasites and diseases. Aspirin, digitalis, Taxol and many other drugs originally came from plants.

“If elevated carbon dioxide reduces the concentration of medicines in plants that monarchs use, it could be changing the concentration of drugs for all animals that self-medicate, including humans,” said Hunter, who has studied monarchs at the U-M Biological Station, at the northern tip of Michigan’s Lower Peninsula, for more than a decade.

“When we play Russian roulette with the concentration of atmospheric gases, we are playing Russian roulette with our ability to find new medicines in nature,” he said.

Earlier work in Hunter’s lab had shown that some species of milkweed produce lower cardenolide levels when grown under elevated carbon dioxide. That finding caught the attention of Decker, who with Hunter designed a follow-up study to look at the potential impact of rising CO2 on the disease susceptibility of monarchs in the future.

They created an experimental system that allowed them to manipulate and measure all the key links in the chain: carbon dioxide levels, toxin concentrations in milkweed leaves, infection by parasites, and monarch susceptibility to those . The fieldwork was conducted in 2014 and 2015.

Inside 40 growth chambers on a hilltop at the Biological Station, they exposed milkweed plants to two different carbon dioxide levels. Twenty chambers were maintained at current global CO2 concentrations of around 400 parts per million, and 20 chambers received 760 ppm of CO2, a level that could be reached well before the end of the century if the burning of fossil fuels continues unabated.

The four milkweed species differed in their levels of protective cardenolide compounds. The most protective species was Asclepias curassavica, commonly known as tropical milkweed. The chamber-raised plants were fed to monarch caterpillars, and each caterpillar got a steady diet of a single milkweed species with known carbon dioxide exposure.

Three-day-old caterpillars were also infected with carefully controlled doses of a common monarch parasite that is distantly related to the malaria pathogen. Ophryocystis elektroscirrha is a protozoan that shortens adult monarch lifespan, impedes its ability to fly and reduces the number of offspring it produces.

Over about two weeks’ time, the infected caterpillars grew to a length of about 2 inches, with striking yellow, white and black bands. Then they pupated inside a hard-shelled chrysalis for about 10 days before emerging as orange-and-black butterflies.

At their Biological Station lab, Decker and Hunter raised hundreds of adult monarchs. The lifespan of each individual—in Michigan, monarch butterflies typically live for about a month—was recorded, and the number of parasitic spores on each carcass was counted.

Piecing together all this data, the researchers were able to determine how changes in levels altered toxin concentrations in the four milkweed species and, in turn, how exposure to those plants affected the monarch’s lifespan and disease susceptibility.

The largest declines in parasite tolerance and butterfly lifespan occurred in monarchs that fed on A. curassavica, a milkweed species in which cardenolide production declined by nearly 25 percent when grown under elevated CO2.

In caterpillars that fed on A. curassavica milkweed grown under elevated CO2, tolerance to the parasite declined by a whopping 77 percent when compared to caterpillars that fed on A. curassavica grown under ambient-level CO2.

Monarchs that fed on A. curassavica grown under elevated CO2 suffered a reduction in lifespan of seven days due to parasitic infection. Parasites reduced mean lifespan by only two days for monarchs that ate A. curassavica grown under ambient CO2 levels.

“We’ve been able to show that a medicinal species loses its protective abilities under elevated ,” Decker said. “Our results suggest that rising CO2 will reduce the tolerance of to their common parasite and will increase parasite virulence.”

In recent years, monarch populations have been declining rapidly. Most discussions of the monarch butterfly’s plight focus on habitat loss: logging of trees in the Mexican forest where monarchs spend the winter, as well as the loss of wild that sustain them during their annual migration across North America.

“Habitat loss, problems during migration and climate change all contribute to monarch declines,” Hunter said. “Unfortunately, our results add to that list and suggest that parasite-infected monarchs will become steadily sicker if atmospheric concentrations of CO2 continue to rise.”

Explore further: Milkweed plants in CO2 growth chambers provide glimpse of biosphere change

Read more at: https://phys.org/news/2018-07-carbon-dioxide-pose-previously-unrecognized.html#jCp

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Lund univ logo

 

WATCH: Insects also migrate using the Earth’s magnetic field

A major international study led by researchers from Lund University in Sweden has proven for the first time that certain nocturnally migrating insects can explore and navigate using the Earth’s magnetic field. Until now, the ability to steer flight using an internal magnetic compass was only known in nocturnally migrating birds.

Lund 1

Bogong moth

Published on 21 June 2018

WATCH: The incredible journey of the bogong moth

“Our findings are the first reliable proof that nocturnally active insects can use the Earth’s magnetic field to guide their flight when migrating over one thousand kilometres. We show that insects probably use the Earth’s magnetic field in a similar way to birds”, says Eric Warrant, professor at Lund University.

Eric Warrant and David Dreyer at Lund University, together with colleagues from Australia, Canada, Germany, and the USA , studied the moth species Agrotis infusa, also known as the Bogong moth, in Australia.

The findings indicate that the insects use both visual landmarks in their flight path and the Earth’s magnetic field, probably making their navigation more reliable.

The researchers believe that moths in northern Europe may use the Earth’s magnetic field in an equivalent manner when flying over the Alps to the Mediterranean.

The moths migrate over a great distance every year, from a large area in southeastern Australia to a specific area of small, cool caves high up in the mountains more than one thousand kilometres away. After a few months in a dormant state, they make the same journey back when summer is over. Besides the Bogong moth, only the North American Monarch butterfly migrates with equivalent precision.

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View from a Bogong cave (Photo: Eric Warrant)
The researchers focused on investigating how the Bogong moth knows in which direction to fly. They found answers by capturing the moths in flight and placing them in a flight simulator where the insects were free to fly in any direction they chose. The flight simulator – invented by team members Barrie Frost and Henrik Mouritsen for studying navigation in Monarch butterflies – was in turn placed in a system of magnetic coils which allowed the researchers to turn the magnetic field in any direction. In addition, they were able to show visual landmarks to the moths.

“By turning the magnetic field and the landmarks either together or in conflict with each other, we were able to investigate how the Bogong moths use magnetic and visual information to direct their flight”, says David Dreyer, adding:

“When the magnetic field and the landmarks were turned together, the moths changed their flight path in an equivalent manner. However, if the magnetic field and the landmarks were turned in conflict with each other, the moths lost their sense of direction and became confused.”

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Bogong Moths on Cave Wall (Photo: Eric Warrant)

Aestivating Bogong moths (i.e. moths in dormancy) clustered on an alpine cave wall near South Ramshead in the Kosciuszko National Park (New South Wales) during the Australian summer. There are approximately 17,000 moths per square metre of cave wall.

Eric Warrant has many years of experience of researching animal night vision and how animals navigate in the dark. Nevertheless, the findings surprised him.

“I believed the studies would show that Bogong moths only use visual cues such as stars, the moon and landmarks to navigate. But that is not the case. They perceive the Earth’s magnetic field in exactly the same way as birds do – and probably for the same reason.”

The next step will be to find out how the moths, despite never having been to the caves before, know that they have arrived at their destination. The researchers also want to locate and characterise the insects’ elusive magnetic sensor.

Besides Lund University, the following higher education institutions and organisations took part in the research work: Queens University in Canada, University of Oldenburg in Germany, Duke University, USA, New South Wales National Parks and Wildlife Service and the Australian Cotton Research Institute, both in Australia.
For raw video material or more images, please contact the press office.

For journalists interested in covering the team’s upcoming field work in Australia, please contact Eric Warrant directly or the press office.

Link to publication: The study is published in the journal Current Biology

Contact:
Eric Warrant, professor
Department of Biology, Lund University
+46 70 496 49 27
eric.warrant@biol.lu.se

David Dreyer, researcher
Department of Biology, Lund University
+46 46 222 78 02
+46 72 568 27 06
david.dreyer@biol.lu.se

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