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Perfume component helps lure male moth pests

Phys.Org

by Mick Kulikowski, North Carolina State University
North Carolina State University researchers have shown that adding a small amount of a chemical used in perfumes—nonanal—to a two-chemical combination of other sex pheromones helped increase the cocktail’s effectiveness in mimicking female fall armyworm “come hither” calls to males.

The findings could eventually help farmers better detect, monitor and control fall armyworm populations, which negatively affect some 350 plant species—including crops like corn and cotton as well as turfgrass and other cultivated grasses.

“Nonanal is emitted by people, birds and even apples,” said Coby Schal, Blanton J. Whitmire Distinguished Professor of Entomology and co-corresponding author of a paper describing the research. “It is a universal attractant that, by itself, doesn’t have much of an effect. But when a certain percentage of nonanal is added to the multi-chemical attractant mixture discovered nearly 40 years ago, it has a highly stimulatory effect—in this case attracting male fall armyworm moths in the lab and then attracting male moths to traps in field experiments.”

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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

• 1 SEP 2022
• 11:25 AM
• BYERIK STOKSTAD

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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

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

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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

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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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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