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Researchers just made it easier—and cheaper—to confuse crop pests

Plant that helps produce behavior-changing pheromones could boost environmentally friendly pest control

A diamondback moth on a leaf
The antennae of the diamondback moth are hypersensitive to airborne mating hormones, which makes them vulnerable to nontoxic pest control. HUANGLIN/ISTOCK

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Each year, pests eat more than one-fifth of the crops grown around the world. Many farmers turn to insecticides to protect their harvest, but some opt for a gentler approach: They perfume their crops with behavior-influencing chemicals called pheromones that can confuse insects and prevent them from finding mates.

But the high price of pheromones—commercial products can cost $400 per hectare—has prevented the widespread adoption of the tactic. Now, a new, cheaper method of manufacturing artificial pheromones could allow more farmers to add this weapon to their arsenals.

“It could revolutionize how pheromones are produced for crop protection,” says Lukasz Stelinski, an entomologist at the University of Florida, Gainesville, who was not involved in the work. “I expect that it’s going to catch on and make pheromone disruption much cheaper and easier to apply in practice.”

Farmers worldwide use more than 400,000 tons of insecticide annually. These pesticides can harm farm workers and cause collateral damage to pollinators and other wildlife. Meanwhile, insects have already evolved resistance to many pesticides, forcing farmers to apply even more.

For some growers, pheromones provide an attractive alternative. Female insects naturally emit pheromones that attract males to mate. By flooding their fields and orchards with fake pheromones designed to appeal to specific insects, farmers can overwhelm these signals and prevent reproduction. Females then lay sterile eggs, which don’t hatch into hungry caterpillars.

The pheromone mating call is usually a mixture of compounds. Traps are designed to attract a particular species—to monitor for the presence of a pest, for example—so a precise cocktail is usually needed. But to sabotage mating, a broad-spectrum component can work because many related species use the same basic compounds as pheromone components.

Synthesizing this chemical smokescreen is nevertheless a complex, expensive proposition. It can cost anywhere from $1000 to $3500 to produce just 1 kilogram of artificial pheromones. Deploying it can cost between $40 and $400 per hectare, depending on the type of pest.

That’s why pheromones are typically only used to protect crops that require relatively little land to turn a decent profit, such as fruits and nuts. Farmers who grow crops that don’t sell for as much per hectare, such as corn or soybeans, often can’t afford to use pheromones to defend their vast fields. It also requires some experience to deploy pheromones effectively. “You’re talking about razor-thin profit lines for a family farm and then asking them to invest not only in the product, but in the labor it takes to get the product in the field,” says Monique Rivera, an entomologist at Cornell University. “It’s a tough ask.”

In a bid to lower costs, Christer Löfstedt, a chemical ecologist at Lund University, and his collaborators in several countries have for the past decade been modifying plants to produce the chemical building blocks needed for synthesizing pheromones. Their crop of choice is Camelina, a flowering plant related to canola with seeds rich in fatty acids—key ingredients in coaxing plants to produce these raw materials.

Löfstedt and colleagues relied on genetic engineering to outfit Camelina with a gene from the navel orangeworm which causes Camelina seeds to produce a fatty acid called (Z)-11-hexadecenoic acid. In insects, this fatty acid is a precursor to mating pheromones. The researchers began to grow their genetically modified Camelina in experimental plots in Nebraska and Sweden in 2016, selectively cultivating the plants that produced the highest amounts of this critical molecule.

After three generations, 20% of the fatty acid content of the seeds consisted of (Z)-11-hexadecenoic acid—enough to suggest the crop could be an efficient source of the raw materials needed to produce pheromones. Next, the researchers purified the oil and converted it into a liquid cocktail of pheromone molecules designed to appeal to the diamondback moth (Plutella xylostella), a pest that presents a particular problem in the Brassica, a group of plants including cabbage, kale, and broccoli.

In 2017, the team tested this pheromone blend in China. They put pheromone traps on sticks about 10 to 15 meters apart in a plot of the leafy Brassica choy sum. The traps worked just as well as commercial synthetic pheromones, the team reports today in Nature Sustainability. Another test in bean fields in Brazil revealed that a single plantmade pheromone could disrupt the mating patterns of the destructive cotton bollworm (Helicoverpa armigera) just as well as a synthetic pheromone.

ISCA Inc., a pest control company in Riverside, California, that participated in the research, estimates it would cost between $70 and $125 per kilogram to grow the Camelina and make the pheromones, less than half the cost of current synthesizing methods. That would put the costs on par with pesticides. The authors note that a liquified version of these pheromones could be dripped on fields, which would require less labor than manually placing traps.

A lower price might make the pheromones accessible to farmers in the developing world, says entomologist Muni Muniappan at the Virginia Polytechnic Institute and State University, who was not involved in the research. But because these pheromones work best when applied to large areas and most farmers in developing regions work small fields, farmers would likely need to work together to see the benefits, he says. “You need to have farmer education and outreach in order to make that successful.”

Getting regulatory approval to grow the genetically modified Camelina on commercial farms would take several years, the researchers note. But existing experimental permits already enable researchers to grow more than enough engineered Camelina to meet the current worldwide demand for pheromone control of diamondback moths and cotton bollworms, says Agenor Mafra-Neto, CEO of ISCA.

Several hurdles remain to applying the approach to other kinds of pests, such as beetles and leafhoppers. Doing so will likely require finding and adding other genes to Camelina. Still, says Junwei Zhu, a chemical ecologist with the U.S. Department of Agriculture, the new work “is a very good start.”


doi: 10.1126/science.ade6979

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Erik Stokstad

Erik Stokstad

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Erik Stokstad is a reporter at Science, covering environmental issues. 

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Bioengineered plants help produce moth pheromones for pest control

Pheromones are often used by farmers for controlling pest insects but the chemical process for producing them is expensive. A method for making them using bioengineered oil plants could be cheaper

ENVIRONMENT 1 September 2022

By James Dinneen

camelina oilseeds
The camelina oilseed plant can be used to make insect pheromones Kurt Miller

A bioengineered oilseed plant can produce a moth sex pheromone molecule used to control insect pests.

Pheromones are chemical signals that cause a behavioural response in members of the same or closely related species. For decades, farmers have used pheromones to keep pest insects away from high-value crops like apples and grapes, for instance by baiting traps with the chemicals or saturating fields with them to make it difficult for the insects to find mates. But the chemical process for making pheromones is too expensive to use for lower-value row crops like maize, soybeans and cotton.

Hong-Lei Wang at Lund University in Sweden and his colleagues bioengineered plants to produce a sex pheromone molecule secreted by two damaging pest species: female diamondback moths (Plutella xylostella) and cotton bollworms (Helicoverpa armigera).

The team used the bacterium Agrobacterium tumefaciens to introduce two genes into the oilseed plant Camelina sativa.

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Using pheromones and mating disruption to fight Tuta absoluta

Tuta absoluta is a pest found in many greenhouses around the world. “Due to the climate change and the movement of goods, Tuta absoluta can now be found in many parts of the world,” says Irina Caraeva from Eco Center. “Generally speaking, if you see mining on the leaves  or the pests themselves – there might be a chance of an infestation.” And this can get quite nasty, not only because they inevitably weaken the plants but also because these get more susceptible to other pathogens.

The risk of using chemical products
Usually, a good practice to prevent that is to use insecticides, but they come with a downside. “The main issue has to do with the beneficial insects present in the greenhouse,” Irina points out. “Insecticides tend to affect those too, which is something growers definitely don’t want.” Another disadvantage of the use of insecticides to counter Tuta absoluta is the residue levels. “First of all, most of the insecticides are quite toxic, and residues can then be found on the produce. You can perhaps use them before the planting, but not during the entire growing season, it’s really not advisable. Additionally, Tuta absoluta develops resistance to most insecticides available on the market, even if there are products that can control the pest, they contain highly concentrated substances that cannot be used immediately before collection since the degradation period is too high.”

Pheromones
That is why Eco Center has devoted its efforts to developing solutions to control greenhouse pests in the most natural and environmentally friendly way. “Pheromones,” Irina points out. “These are species-specific, which means that they will affect only a given insect. In this way, a grower can be sure that beneficial insects don’t get harmed. At Eco Center, we have developed many pheromone products, with the most recent addition of the Tuta Protect – a mating disruption product.” The Eco Center also makes pheromone lures for monitoring tomato leaf miner to go together with their Delta Traps. “These are designed specifically to monitor the insect population in a cost-efficient and environmentally friendly way. They will help the growers to make decisions on further application of other pest management actions.”

Mating disruption
Irina continues to explain that before planting, a grower should start the monitoring process by installing a couple of Delta traps with pheromone lures. At the same time, if traps indicate the need for control of pests, Eco Center has come up with another solution. “Mating disruption,” she says. “These pheromone dispensers contain 170-180 milligrams of pheromone. Bluntly put, the mating disruption dispensers create “false pheromone trails” that affect Tuta absoluta males, which interferes with their mating finding behavior.”

Irina says that Eco Center is constantly working to include more insects in their pheromones catalog. “Right now, we are testing our products for the pink bollworm, which are mainly asked by our customers from the Middle East and Africa. At the same time, we are in the process of figuring out the best pheromone solution for the most common cannabis pests. Hopefully, we’ll get into that market soon,” she concludes.

For more information:
Eco Center
MD-2005, Moara Rosie 5E str.
Chisinau, Republic of Moldova
+373 68979696
info@ecocenter.md 
ecocenter.md

Publication date: Mon 29 Aug 2022
Author: Andrea Di Pastena
© HortiDaily.com

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Fall armyworms were a miss this year

ossyugioh/Getty Imageshands moving and inspecting corn plants for leaf damaged by fall armyworms

FROM THE FIELD: Damage to corn leaves in the field is a sign of fall armyworm infestation. The problem is the pest is becoming resistant to its most popular control mechanism — pyrethroids.

Research on mating disruptors may help offset growing pyrethroid resistance.

Mindy Ward | Aug 24, 2022

fps-generic.jpg

Fall armyworm invasion. It is often a boom-or-bust cycle. This year was a bust, and that is good news for farmers. Still researchers know that will not always be the case, and they continue searching for ways to mitigate fall armyworm infestations, such as altering the pest’s behavior.

Last year was the biggest outbreak of fall armyworms across the U.S. in 30 years, said Kevin Rice, the former University of Missouri Extension entomologist who is now the director of the Alson H. Smith Jr. Agricultural Research and Extension Center at Virginia Tech.

“We expect that fall armyworm outbreaks may occur more often because of our milder winters,” he explained during the MU Pest Management Field Day in July.

Fall armyworms typically only overwinter in the tip of Florida and in Texas. However, researchers find that now, because of milder winters, they are overwintering in higher latitudes, but their natural enemies are not. “So they get a jump-start; they get a higher overwintering population,” Rice said.

He said farmers should beware of potentially more fall armyworm outbreaks on a more regular basis than every 30 years.

Problems with resistance

Fall armyworm is one of the fastest growing insects on earth, Rice warned. “They’re called armyworms because they move into field and devastate it like an army,” he said.

Staying ahead of them once they appear can be difficult because the larvae have a wide host range of at least 80 plants, but they prefer grasses such as corn, sorghum, bermudagrass and tall fescue. They can also feed on alfalfa, barley, oats, ryegrass, vegetables and soybeans. Armyworms tend to move quickly into new areas in large numbers.

The good news with fall armyworm is there are integrated pest management tools for control. The bad news is the pest is becoming resistant to one of those measures — pyrethroids.

kochievmv/Getty Imagesfall army worm on a corn leaf

CLOSE UP: Fall armyworms feeds on corn, leaving behind a moist sawdust-like frass near the whorl and upper leaves of the plant.

Rice noted that several states neighboring Missouri reported pyrethroid-resistant fall armyworm populations. Since females fly over thousands of miles, he added, farmers can assume those resistant genes are being passed and mixing throughout the population in surrounding states. Therefore, farmers should not be using pyrethroids for treatment of fall armyworm infestations moving forward.

While Rice is taking that tool out of the pest management toolbox, his research lab is hoping to add another control means back in.

Search for solutions

Universities such as Mizzou are working on a new management option for fall armyworms using mating disruption.

High-emission-rate “mega-dispensers” are used for sex pheromone mating disruption of moth pests. These dispensers suppress mating and reduce crop damage when deployed at very low to moderate densities. “It confuses them, and often they don’t lay eggs,” Rice noted.

The research focuses on whether these mega-dispensers work on a per-acre basis and at what levels. It is still in the “very preliminary stage,” he said, but trials were set up in Alabama and Missouri this summer. “We’re quantifying it, to see if the process works.”

Rice said these types of behavioral mechanisms might be good, viable options in the future as the industry loses chemistries to fight the fall armyworm.

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‘Using insect biology against themselves’: New type of pesticide uses caterpillar pheromones to stop pests from mating

Gabe Barnard | St. Louis Post Dispatch | August 3, 2022

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They drop out of the sky like paratroopers. Credit: Missouri Pest Monitoring Network
They drop out of the sky like paratroopers. Credit: Missouri Pest Monitoring Network

The caterpillars are the larvae of the fall armyworm moth, a planetary crop invader. The annual toll of their attacks is at least $300 million for farmers in the U.S., and billions of dollars around the globe.

But now scientists from the University of Missouri are on the edge of a new frontier in pest control: They are filling fields with a chemical — not a pesticide — that replicates the pheromones of the moth, overwhelms its senses and stops it from mating, essentially using the insect’s own biology against it. The system could reshape pest control in the U.S., and be even more useful in countries where subsistence farming is common and access to genetically modified crops isn’t.

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Female moths have glands that emit the pheromone, a compound specific to the species. They pump out the pheromone into the air at night, and male moths use pheromone receptors in their antennae to sense the chemicals and find the female. Then they mate. Females can produce up to 2,000 eggs in their five-day lifespan.

The researchers’ experiment is designed to thwart the moths’ romance: Plastic pheromone strips are attached with a binder clip to wooden stakes in the ground. The strips release clouds of pheromones so intense the males can’t pinpoint a mate.

This is an excerpt. Read the original post here

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Using Integrated Pest Management to Reduce Pesticides and Increase Food Safety

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Integrated Pest Management Innovation Lab

Mar 06, 2018

Photo: A farmer sprays pesticides on cucurbit crops in Bangladesh.
Photo: A farmer sprays pesticides on cucurbit crops in Bangladesh.

Written by Sara Hendery, Communications Coordinator of the Feed the Future Innovation Lab for Integrated Pest Management

In 2017, thousands of beetles and weevils moved into Ethiopia’s Amhara region. Like most living things, they were hungry, but their appetites desired a specific earthly delicacy: weeds.

Zygogramma, the leaf-feeding beetle, and Listronotus, the stem-boring weevil, were released in Ethiopia by Virginia State University, collaborators of the Feed the Future Innovation Lab for Integrated Pest Management, funded by USAID and housed at Virginia Tech. Zygogramma and Listronotus combat Parthenium, an invasive weed that threatens food security and biodiversity, causes respiratory issues and rashes on human skin, and taints meat and dairy products when consumed by animals. Biological control and other holistic agricultural methods are specialities of the Integrated Pest Management (IPM) Innovation Lab. Its team of scientists and collaborators generate IPM technologies to fight, reduce and manage crop-destroying pests in developing countries while reducing the use of pesticides.  

The application of pesticides is a major threat to human health. In sub-Saharan Africa, more than 50,000 tons of obsolete pesticides blanket the already at-risk land. Pesticides can taint food, water, soil and air, causing headaches, drowsiness, fertility issues and life-threatening illness. Especially vulnerable populations are children, pregnant women and farmers themselves; hundreds of thousands of known deaths occur each year due to pesticide poisoning. Pesticides often increase crop yields, but an abundance of crops is anachronistic when the cost is human life.

In a small community in Bangladesh, farmers used to rely on pesticides to manage insects and agricultural diseases destroying crops, but community members began to develop symptoms from the excessive pesticide use, and, more than that, children were doing the spraying. The IPM Innovation Lab implemented a grafting program in the community that generated eggplant grafted varieties resistant to bacterial wilt. Eggplant yields increased dramatically and purchases of chemical pesticides dropped, which meant safer and healthier produce for families.

This story is one of many. The IPM Innovation Lab taps into a collection of inventive technologies in both its current phase of projects in East Africa and Asia, and since its inception in 1993, to enhance the livelihoods and standards of living for smallholder farmers and people across the globe:

  • In Vietnam, dragon fruit is covered in biodegradable plastic bags to protect the plants from fungal disease.
  • In Niger, the release of parasitoids eliminates the pearl millet headminer.
  • The spread of coconut dust inside seedling trays grows healthy plants in India.
  • Parasitic wasps destroy the papaya mealybug from India to Florida.
  • Trichoderma, a naturally occurring fungus in soil, fights against fungal diseases in India, the Philippines and elsewhere.  
  • Cuelure bait traps save cucurbits from fruit flies in Bangladesh.
  • Eggplant fruit and shootborer baits protect eggplants from insect damage in Nepal, India and Bangladesh.

Pesticides do not necessarily eliminate pest invasion; they eliminate even the “good” insects on plants. Insects often develop resistance to popular chemicals when applied frequently, so not only is chemical spraying sometimes unnecessary, it is excessive.

Tuta absoluta, for example, is a tomato leafminer destroying tomato crops across the globe. In Spain, in the first year of the pest’s introduction, pesticides were applied 15 times per season, but the pest is resistant to pesticides and is so small (about the size of a stray pencil mark) that it often burrows inside the plant rather than around it. The IPM Innovation Lab and its collaborators generated one-of-a-kind modeling to track the movement of the species and introduced pheromone traps and neem-based bio-pesticides to help manage its spread, further ensuring the implementation of a series of technologies, rather than just relying on one, to reduce crop damage. The age-old saying “two heads are better than one” is accurate — just ask Zygogramma and Listronotus.

In developing countries, it is difficult to regulate the amount of chemical pesticides that make it onto crops, thus increasing the risk that chemicals will have a dramatic effect on the safety of food and the potential for exposure to foreign markets. One of the reasons pesticide over-application is common in developing countries is due to misinformation. In Cambodian rice production, pesticides are often misused because labels are printed in a foreign language; it is common that farmers mix two to five pesticides, resulting in pesticide poisoning. The IPM Innovation Lab’s project in Cambodia reduces the number of pesticides in rice production by introducing host-plant resistance and biological control.

Also, a fundamental practice of the IPM Innovation Lab is conducting trainings and symposia for farmers and IPM collaborators across the world to educate on the use and implementation of IPM technologies, further reducing the risk of possible harm to crops and human life. Additionally, IPM Innovation Lab partners with agriculture input suppliers and markets in project communities to ensure that bio-pesticides and IPM materials such as traps are readily available and that the purchase of pesticides are not the only option.

Ultimately, when you spray, you pay. The IPM Innovation Lab prioritizes both human and plant health by reducing the use of pesticides, and with the human population growing by the thousands every day, it is crucial that food is not only abundant but also safe and healthy to eat.

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Effective Management Remains Elusive for Beetle That Eats Almost Anything

ENTOMOLOGY TODAY1 COMMENT

The Japanese beetle (Popillia japonica) is a widely known invasive species in North America. Adults feed on more than 300 plant species and can be downright difficult to manage. A new guide in the open-access Journal of Integrated Pest Management reviews their invasion history, ecology, and management. (Photo by Emily Althoff, originally published in Althoff and Rice 2022, Journal of Integrated Pest Management)

By David Coyle, Ph.D.

David Coyle, Ph.D.

Every spring, gardeners across this great land get excited as the seasons turn. All these new plants we put in last fall, or the new flower beds, or the growing garden—take your pick, really—are going to look awesome this year. (We’re all convinced of this.) I’m one of these people, an amateur flower gardener and tree aficionado. And every year, for the most part, things do look awesome, until about May, when the inevitable Japanese beetle emergence happens.

Popillia japonica, commonly known as the Japanese beetle, is native to Japan and first arrived in the U.S. in 1916. It is now established in 28 states and three Canadian provinces, has been detected in 13 additional states, and—let’s face it—it’s only a matter of time before it reaches the rest of the continent. Adults feed on foliage of more than 300 different species of plants, and the larvae are root feeders, preferring grasses. Japanese beetle larvae are a problem in turf, and adults are problematic on basically everything else. Trees? Check. Shrubs? Check. Flowers? Check. Garden plants? Check. Crops? Sometimes, yes, so check. Pretty much anything green is fair game as a food plant. Even geraniums, which are toxic to adults, don’t deter feeding. Adults that feed on geraniums become temporarily paralyzed, but once they regain bodily function they go right back to eating the same plant. These are truly fascinating and frustrating creatures.

Emily Althoff

Because of the Japanese beetle’s wide range and very in-your-face impacts, we have learned much about this system. But now, a paper published this month in the Journal of Integrated Pest Management reviews what we do and don’t know about P. japonica management. I spoke with the lead author, Emily Althoff, a Ph.D. student in entomology at the University of Minnesota, about challenges and opportunities associated with this well-known and universally loathed (I’m assuming) pest.

Coyle: What’s the best control option for the residential homeowner who has flowerbeds, shrubs, and flowering trees (asking for a friend)? What about someone who is very opposed to pesticides?

Althoff: One of the best home garden control options for those hesitant about insecticides is to hand pick the beetles off the plants in the mornings and place them in soapy water. While this is time consuming, it prevents the beetles from producing aggregation compounds and inducing attractive plant compounds as well, both of which would attract more beetles.

This is eye-opening to me, as I’ve never considered the impact of the aggregation pheromones. By removing adults in the morning, you can lessen their impact because they don’t call as many friends to the food party. Great advice.

A lot of people use different types of traps for Japanese beetles, and as an entomologist I’ve looked at a lot of these. So, tell me, why are there so many ridiculous ineffective traps on the market? Is the public that desperate to get rid of these things that literally any company can produce something that vaguely resembles a bug trap and people will buy it?

I think that the traps are a result of a few different things. I think it is very evident the pheromone and volatile cues are effective at attracting beetles. The issue is that they work too well in this regard, causing more beetles to arrive than the trap can hold. The commercially available traps are very effective at monitoring Japanese beetle activity. At the University of Missouri, these are used in the IPM pest monitoring network to quantify Japanese beetle emergence and populations throughout the state and report this information to growers every week.

However, the commercial traps are not designed to kill enough beetles to make a difference in damage rates in agricultural fields or gardens. We did count the number of Japanese beetles that bucket traps hold and found that approximately 3,500 beetles fill the trap. The traps are so effective at attracting Japanese beetles that they can fill up in as little as two days.

Japanese beetle larvae (Popillia japonica)
Japanese beetle leaf damage
Japanese beetle (Popillia japonica) traps are very effective in monitoring their presence but not in reducing their numbers. "The issue is that they work too well in this regard, causing more beetles to arrive than the trap can hold," says Emily Althoff, a Ph.D. student in entomology at the University of Minnesota. "However, the commercial traps are not designed to kill enough beetles to make a difference in damage rates in agricultural fields or gardens. We did count the number of Japanese beetles that bucket traps hold and found that approximately 3,500 beetles fill the trap. The traps are so effective at attracting Japanese beetles that they can fill up in as little as two days." (Photo by Raymond Cloyd, originally published in Althoff and Rice 2022, Journal of Integrated Pest Management)

Do you think Japanese beetles have crowded out any native species? Or did they fill a new niche?

While Japanese beetles are numerous and can defoliate entire trees and create severe economic damage to agriculture, in my opinion, their polyphagous nature prevents them from competing with native species for resources. Unfortunately, their damage to some commodities, like grapes, can actually create more feeding opportunities for other native beetles.

What’s the most Japanese beetles you’ve ever seen on one plant?

Too many to count!

Can confirm. I’ve seen this level of infestation too! Any other Japanese beetle tidbits of knowledge you’d like to share?

In the early days of the beetle’s arrival, many, shall we say, unique solutions were suggested for its management including the mobilization of Girl Scout and Boy Scout troops and paid bounties for beetles—a quart of beetles could get you 80 cents. Additionally, early management strategies such as aerial arsenic sprays were written about by Rachel Carson in her work Silent Spring.

Japanese beetles are here to stay, and to those of us doing battle with these voracious folivores, well, I wish I had better news. Management is either challenging or labor-intensive, depending on your perspective. On the other hand, if you’re using them in feeding assays, it’s really easy to collect ample amounts for your trials (make lemonade out of lemons, I always say). For those of you on social media, it’s pretty easy to track Japanese beetle emergence across their range because, the minute they’re out, extension folks are posting about them. Good luck, fellow gardeners!

Read More

Japanese Beetle (Coleoptera: Scarabaeidae) Invasion of North America: History, Ecology, and Management

Journal of Integrated Pest Management

David Coyle, Ph.D., is an assistant professor in the Department of Forestry and Environmental Conservation at Clemson University. Twitter/Instagram/TikTok: @drdavecoyle. Email: dcoyle@clemson.edu.

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New Guide Offers IPM Tips for Japanese Beetles in Soy and Corn

April 29, 2019

How Do We Know Which Invasive Plant Pests Will Be the Next Big Threats?

June 7, 2021

Biological Control for Hemlock Woolly Adelgid: Where Do We Stand?

October 7, 2019 Research NewsDave CoyleEmily Althoffintegrated pest managementinvasive insectsInvasive speciesJapanese beetleJournal of Integrated Pest ManagementPopillia japonicatraps

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How the discovery of a moth sex gene could lead to crucial insecticide

JANUARY 8, 2022by Study FindsSHARES1ShareTweet

MEDFORD, Mass. — European corn borer moths are one of the biggest causes of damage to crops, tunneling their way through vegetables and fruit. It costs nearly $2 billion a year in the U.S. to monitor and control the hungry insect. One recent study reveals a way to predict mating habits and develop a possible “insecticide” to stop reproduction comes from the European corn borer moth’s reproductive genes.

Researchers have identified a gene in moths that controls their sex lives. This gene sheds light on the evolution of changing sexual habits. Control of this gene could become a method of pest control, thereby protecting crops from moths.

“This is the first moth species out of 160,000 in which female signaling and male preference genes have both been identified. That provides us with complete information on the evolution of mate choice and a way to measure how closely these choices are linked to evolving traits and populations,” says co-author Professor Astrid Groot, of the University of Amsterdam, in a statement.

There are two types of European corn borer, called E and Z, with sex mainly occurring only within each group in the wild. Groot helped identify the gene controlling the pheromone difference in E and Z females.

“That means we now know – at the molecular level – how chemical matchmaking aids in the formation of new species. Similar genetic changes to pheromone preference could help explain how tens of thousands of other moth species remain separate,” explains corresponding author Erik Dopman, a professor of biology in the School of Arts and Sciences at Tufts University.

The study follows the discovery of the blend of molecules the female emits to draw mates from miles away. Known as “assortative mating,” a signal is sent by the female and must be preferred by males of the same species to safeguard the survival of the species. The gene, expressed in the brain of the male and connected to its antennae, produces a protein which enables him to smell the females’ pheromones, chemical signals used to attract mates.

The researchers were able to determine anatomical differences in the male and link them to their attraction to E or Z females. These included the reach of olfactory sensory neurons into different parts of the moth brain. An analysis showed females can vary their signals. The gene, named bab, changes the male’s preference for a particular cocktail.

The European corn borer is the primary target for “Bt corn,” one of the most successful genetically modified crops in the U.S. This crop expresses insecticidal proteins derived from the bacterium, Bacillus thuringiensis. It is an effective control of the moth in the U.S., however, corn borers in Canada are now evolving resistance to another variety.

“Our results can help to predict whether Bt resistance could spread from Nova Scotia to the Corn Belt of the U.S., or whether assortative mating could prevent or delay it. Bt corn has enabled a huge reduction in the use of chemical insecticides, and it should be a high priority to preserve its ecological benefits as long as possible,” adds co-author Dr. David Heckel, of the Max Planck Institute for Chemical Ecology in Germany.

Findings are published in the Journal Nature Communications.

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Sam Jones with IPS:

“Alternative tools to manage insect pest outbreaks have never been more important”

Crop protection is vital for every grower; you do not put all that effort into growing your crops just for them to get eaten or get ill. One method to fight pests is pheromones. International Pheromone Systems (IPS) develops, produces, and supplies insect semiochemical-based products and trapping systems for its customers, which “are used to monitor and control insect pests in a wide range of settings, including agriculture, horticulture, forestry, storage facilities, and in the home and garden,” Dr. Sam Jones from IPS says.

Right: Dr. Sam Jones with IPS

The importance of pheromones
“As fewer pesticides become available to growers, the availability of alternative tools such as pheromones to manage insect pest outbreaks has never been more important. Pheromone based products such as pheromone lures help growers manage pests in a sustainable and environmentally friendly manner. Although most biopesticides are not as efficient as traditional pesticides, they are far more ecofriendly and species specific, enabling growers to harness the benefits of natural predators which are often able to maintain pest populations below a harmful level. “

This is where IPS comes in. With the help of pheromones – chemical signals insects use to, for instance, find a mate – growers can fight pests and ensure healthier crops. With the aid of such pheromones, the insects are lured into a trap and can no longer hurt the crops or the pollinators buzzing around in the greenhouse. 

Trap Color Trials in aubergine – monitoring for whitefly

Sam explains in detail how two ways of using pheromones work: “Mass trapping and Mating Disruption are two strategies used by many growers to control pests. Mass trapping involves using a greater density of pheromone traps to control a pest population, whereas mating disruption uses pheromone dispensers to saturate the air with a sex pheromone. Usually, it is the male sex that uses the pheromone to locate females, which then quickly become confused by the large number of dense pheromone plumes. This results in them failing to locate a mate.”

Beneficial attractant testing in raspberry crops 

When pheromones do not work
Although pests like thrips, moths, beetles, mealy bugs, and scale insects can be fought with pheromones, not all insects are susceptible to them, Sam says. “Aphids and whitefly, for example, do not use sex or aggregation pheromones (pheromones that attract the opposite sex or both sexes respectively) and therefore monitoring of these pests predominantly relies upon the use of yellow sticky boards or rolls. Visual attraction alone is significantly less effective than a combination of olfactory (e.g. a pheromone) and visual, and yellow boards in particular are non-discriminatory, often catching high numbers of beneficial insects.”

Luckily, there seems to be an alternative: kairomones, another form of semiochemical. Unlike pheromones, which are used among individuals of the same species, kairomones are chemical signals used between different species. As Sam states, “kairomones have been successfully used to enhance attraction of many insect pests, and at IPS we are investigating whether specific chemicals can be used for pests such as aphids and whitefly.”

The pheromones can be applied in polytunnels and glasshouses, in low-tech and high-tech environments alike. Moreover, the pheromones are not only relevant for vegetable and fruit cultivators; flower growers, too, can benefit from this method as IPM produces lures for many moth pests of floral cultivation as well.

Trap/Lure testing in cucumber crops – using a pheromone lure for the Western Flower Thrip, Frankliniella occidentalis

Pesticides fall, pheromones rise
The interest in pesticide-free crops has grown considerably with consumers preferring produce that is grown in the absence of harmful pesticides. Pheromone lures and trapping systems support growers in achieving this. “Recently”, Sam explains, “the EU has banned a wide variety of different pesticides that were deemed to be hazardous to humans and the environment leaving growers with fewer options. Growers are adapting to these changes by adopting Integrated Pest Management plans with a reliance on strategies that do not use synthetic pesticides. There has been considerable growth in the biological pesticide sector in recent years as these are adopted as alternatives. While most are not as effective as conventional pesticides, the efficacy of newer products continues to improve and their increased selectivity ensures that they are better for the glasshouse ecosystem. ”

“As pesticides continue to become phased out, there will undoubtedly be considerable challenges to maintain profitable yields that are sufficient to feed a growing population. It will likely require intelligent use of all available strategies, including biological, physical, and traditional methods. Pheromones will continue to have an important role to play in achieving these goals.”

For more information:
International Pheromone Systems
www.internationalpheromones.com 

Publication date: Wed 20 Oct 2021
Author: Arlette Sijmonsma
© HortiDaily.com

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Why I’m testing what invasive insects can see and the smells they like

August 18, 2021 10.59am EDT

Author

  1. Quentin GuignardPhD Candidate, Chemical & Visual Ecology, University of Pretoria

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Quentin Guignard does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.

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_Sirex noctilio_ is an invasive woodwasp.
Sirex noctilio is an invasive woodwasp that causes huge damage. Understanding what attracts it can help repel it. Ludwig Eksteen

Dr Emmett Brown, Dr Victor Frankenstein and Dr Henry Jekyll are just three of the “crazy” scientists who populate fiction. Their methods were controversial and revolutionary – and I have always been especially drawn to the character of Dr Frankenstein, who was created by the English novelist Mary Shelley in 1818. I am fascinated by how he used electricity to study and understand the living. Every movement, feeling or thought is the result of electrical current in our body.

As an electrophysiologist, I see myself as a modern, real version of Dr Frankenstein: I use electrodes to study and understand living organisms. Given the tragedy at the heart of Frankenstein, this may sound evil. But in fact, using ethical practices to insert electrodes into living creatures can help research in human health, agriculture and forestry and create the path to greener ecology and conservation.

This sort of work also has enormous economic value because it can help reduce the damage done by invasive insects. A recent study estimated the losses and negative effects of invasive insects at US$70 billion annually. Other research suggests that insects destroy one fifth of crops produced annually worldwide. The figure can be higher in developing countries.

How does inserting electrodes into insects tackle these problems? Simply, it helps scientists to understand, in the first instance, what attracts insects to different crops. It’s then possible to design ways to trap them. This is what I’m doing in my PhD research, focused on an invasive woodwasp, Sirex noctilio. It kills pine trees and does major damage in the forestry sector worldwide. But by testing what colours and smells attract the insect, I have developed compounds I hope will trap and divert the wasps from pine trees.

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What attracts insects

Pheromones are odours released by an insect which have a strong attractive effect on another insect’s behaviour. For example, male insects can smell a female willing to mate and are strongly attracted.

Insects are also attracted to what they perceive as a “beautiful” colour. As humans, we possess three pigments that absorb light, in the red, green and blue part of the visible spectrum. Colour blind people usually have a defective red pigment and struggle to differentiate colours such as green, orange and red. Most insects in the Hymenoptera order – like wasps, bees and hornets – possess three photoreceptors (for detecting green, blue and ultraviolet) in their eyes. This means they are less good at distinguishing warm colours than us, but they are able to see ultraviolets.

So, to trap these insects and prevent them from targeting crops or forestry plantations, scientists copy the insects’ natural pheromones. From this, and sometimes also synthesising colours that are pleasing to the insects, lures can be created to draw them away from particular crops or plant species.

By putting electrodes in the Sirex noctilio’s antennae, I am able to record the electric current from those antennae to the brain and to visualise on a computer when the insect can smell a specific pheromone. This means I can see what the insect can smell. I can also insert very small electrodes into the insects’ eyes, testing which colours they can see.

The electro-retinography set-up used to examine the wasps. Author supplied

Armed with this information, we can now craft a selective “trap” – lures that keep the wasps away from the pine trees they usually target. These lures are a blend of a few pheromone compounds and the colours that are visible to the woodwasp. Once attracted in the trap, the invasive pest is killed and won’t do further damages to the area that needs to be protected.

Huge benefits

The next step will be to start field trials that put the compounds’ viability to the test.

Global research has already shown that pheromone traps of this nature, used in the field, can have tremendous positive effects. One study followed the efficiency of such traps in citrus plantations in Brazil for 12 years. The authors estimated that up to 50% crop loss was prevented. This represented a benefit of between $2,655 and $6,548 for each dollar spent on the pheromone research.

Of course, my research is just one piece of a large puzzle. Scientists are trying a number of approaches to save crops and plantations around the world from invasive insects. These range from transgenic crops to sterile insects; from introducing a new species as a biological control agent to creating new types of pesticides.

What’s especially promising about creating pheromone and colour traps, however, is that they can be extremely targeted. More traditional methods of pest control, like spraying pesticide, can harm other, non-invasive species. But if we find that our traps are negatively affecting such species, we’ll remove them and try a more specific blend of compounds that we hope will only eradicate the wasps from pine plantations.

This article won the Science Communication Award in a competition hosted by The Conversation Africa and the DST-NRF Centre Of Excellence In Tree Health Biotechnology.

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Online resources available from BCPC:

·        PESTICIDE MANUAL

·        UK PESTICIDE GUIDE

·        MANUAL OF BIOCONTROL AGENTS

·        GM / BIOTECH CROPS MANUAL (Free Access)

·        IDENTIPEST (Free Access)

·        ·      

   


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