Rose essential oil: A safe pesticide for organic agriculture
Researchers find that rose essential oil activates tomato defense genes and attracts herbivore predators that protect the plants.
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RESEARCHERS AT TUS HAVE DISCOVERED THAT ROSE ESSENTIAL OIL (REO) ACTIVATES TOMATO PEST-DEFENSE GENES AND ATTRACTS HERBIVORE PREDATORS. THEREFORE, REO COULD BE USED AS AN ENVIRONMENTALLY FRIENDLY PESTICIDE IN ORGANIC FARMING.
view moreCREDIT: GEN-ICHIRO ARIMURA FROM TOKYO UNIVERSITY OF SCIENCE (TUS), JAPAN
Plants-derived essential oils (EOs) find applications in various industries, such as detergents, cosmetics, pharmacology, and food additives. Moreover, EOs have an exceptional safety profile, and their numerous bioactivities greatly benefit human health. Beyond these benefits, EOs have also been found to illicit insect-repellent responses by inducing neurotoxic effects.
Terpenoids are abundant in plant EOs and have garnered widespread attention as they can regulate plant defense responses by regulating the expression of defense genes. For example, soybean and komatsuna plants, when grown near mint, experience a significant improvement in defense properties and become resistant to herbivores. This phenomenon occurs through a process known as “eavesdropping,” wherein volatile compounds are released from the mint plant. These volatile compounds trigger the activation of defense genes, protecting against potential herbivore threats.
Today, applying chemical pesticides is the method of choice for crop protection, but the damage they cause to the environment and ecosystems, along with the need to increase food productivity, stresses the need for safer alternatives. Thus, there is an urgent need for investigation of plant defense potentiators. In this regard, the availability of EOs makes them attractive candidates as environmentally friendly plant defense activators. However, there is a lack of sufficient proven examples to meet the demand.
To address this, a research team led by Professor Gen-ichiro Arimura from the Department of Biological Science and Technology at the Tokyo University of Science (TUS) assessed the efficacy of 11 EOs in activating tomato defense responses. “EOs used as fragrances for various purposes contain odor components, which may have the ability to work like volatile compounds in conferring pest resistance. We aimed to investigate the effects of these EOs on plants’ insect pest resistance,” says Prof. Arimura. The team’s findings were published in the Journal of Agricultural and Food Chemistry on March 18, 2024.
The team profiled the effects of terpenoid-enriched EOs on tomato plants. They applied ethanol-diluted solutions of 11 different EOs to the soil of potted tomato plants, performed molecular analyses to study the gene expression inside leaf tissue, and observed that rose EO (REO) increased the transcript levels of PIR1 and PIN2, the genes involved in plant defense. Additionally, tomato plants treated with REO exhibited reduced leaf damage caused by the Spodoptera litura (a moth species) larvae and Tetranychus urticae (a mite pest). Furthermore, to explore the possibility of broader application, the researchers conducted a field experiment to measure REO activity in field conditions. They observed a 45.5% reduction in tomato pest damage compared to the control solution. The researchers believe that REO could serve as a viable alternative to pesticides during the winter and spring seasons when pest infestation is less severe and could potentially reduce pesticide usage by almost 50% during summers.
Explaining the research findings, Prof. Arimura says, “REO is rich in β-citronellol, a recognized insect repellent, which enhances REO's efficacy. Owing to this, damage caused by the moth larvae and mites was significantly minimized, confirming REO as an effective biostimulant. The findings also showed that a low concentration of REO did not repel T. urticae but attracted Phytoseiulus persimilis, a predator of these spider mites, thus exhibiting a dual function of REO.”
Overall, the study highlights the role of β-citronellol-enriched EO in activating defense genes in tomato leaves. Additionally, it provides evidence that REO is an effective biostimulant for enhancing plant defense against pests, which is also safe as it does not lead to phytotoxicity or leave any toxic residues behind. “Our study suggests a practical approach to promoting organic tomato production that encourages environmentally friendly and sustainable practices. This research may open doors for new organic farming systems. The dawn of potent environmentally friendly and natural pesticides is upon us,” concludes Prof. Arimura.
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Reference
DOI: https://doi.org/10.1021/acs.jafc.3c08905
About The Tokyo University of Science
Tokyo University of Science (TUS) is a well-known and respected university, and the largest science-specialized private research university in Japan, with four campuses in central Tokyo and its suburbs and in Hokkaido. Established in 1881, the university has continually contributed to Japan's development in science through inculcating the love for science in researchers, technicians, and educators.
With a mission of “Creating science and technology for the harmonious development of nature, human beings, and society," TUS has undertaken a wide range of research from basic to applied science. TUS has embraced a multidisciplinary approach to research and undertaken intensive study in some of today's most vital fields. TUS is a meritocracy where the best in science is recognized and nurtured. It is the only private university in Japan that has produced a Nobel Prize winner and the only private university in Asia to produce Nobel Prize winners within the natural sciences field.
Website: https://www.tus.ac.jp/en/mediarelations/
About Professor Gen-ichiro Arimura from Tokyo University of Science
Dr. Gen-ichiro Arimura is a Professor in the Department of Biological Science and Technology at the Tokyo University of Science, Japan. Prof. Arimura earned a Ph.D. in 1998 from the Hiroshima University Graduate School, Japan. He researches the molecular mechanisms of plant-insect interactions and the biotechnology applications of plant scents in inter-organism communication. He has published over 100 peer-reviewed papers since 1996.
JOURNAL
Journal of Agricultural and Food Chemistry
METHOD OF RESEARCH
Experimental study
SUBJECT OF RESEARCH
Not applicable
ARTICLE TITLE
Novel potential of rose essential oil as a powerful plant defense potentiator
ARTICLE PUBLICATION DATE
18-Mar-2024
Organic farms can have mixed effects on pesticide use depending on their neighbors
Organic farming reduces pesticide use in nearby organic fields, while increasing it in conventional fields
UNIVERSITY OF CALIFORNIA - SANTA BARBARA
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ASHLEY LARSEN
view moreCREDIT: UC SANTA BARBARA
(Santa Barbara, Calif.) — Organic agriculture may be as old as dirt, but that doesn’t mean its impacts are fully understood. A team of scientists in the United States and Canada are doing their part to change that.
Researchers at UC Santa Barbara, University of British Columbia, and University of Colorado Boulder discovered that organic farming significantly affects the amount of pesticide used in neighboring fields. The study, published in Science, found that the impact depends on the density and spacing of organic and conventional fields, and clustering organic fields together could provide the most benefits for all farmers.
“We find that organic cropland generally leads to a decrease in pesticide use on nearby organic fields,” said lead author Ashley Larsen, an ecologist at UCSB’s Bren School of Environmental Science & Management. “In contrast, organic agriculture leads to a small, but significant, increase in pesticide use on nearby conventional fields.” The authors suspect that the different responses reflect different reliance on natural pest control methods, although they admit the mechanisms are difficult to test with their data.
There’s been a push to increase organic production in the U.S., which begs the question of how this will affect pests and pest control for other farms. Most pesticide studies have focused on the field level, Larsen said, comparing metrics like biodiversity, soil health and pesticide use between organic and conventional fields. However, agricultural pests and their predators move beyond field boundaries. So the group sought to understand these interactions between fields, which they call “spillover effects.”
Precisely why this is the case is unclear but, the researcherrs said, it may have to do with how the pest-control measures taken by organic farms affect the larger ecosystem. “Organic fields leverage the benefits of natural enemies that reduce the number of pests on their fields, like birds and bugs that eat smaller problematic pests,” said co-author Claire Powers, a former graduate student at Bren now pursuing her doctorate at CU Boulder. These predators and pests then venture into neighboring fields for shelter and food.
Organic farmers can benefit from a greater abundance or persistence of their pests’ natural enemies, which can be harmed by chemical pesticides in conventional fields. Thus, organic farmers could benefit from clustering together.
On the other hand, an influx of insects from organic fields could drive up the use of chemical pesticides in conventional fields, since these fields have smaller, less effective populations of those beneficial species.
Unfortunately, when organic and conventional farms are distributed evenly, both kinds of farmers often lose out. “Clustering organic fields concentrates the pest control benefits to organics and reduces the costs to conventional fields,” Larsen said. And, as the share of organic agriculture increases, the beneficial effect of organic fields on one another starts to dominate.
“The big takeaway from this research is to stack organic fields next to organic fields and conventional fields next to conventional fields,” added Powers. Doing so could reduce pesticide use overall, benefitting both the environment and farmers’ bank accounts.
These pithy conclusions are the culmination of an involved process. The authors faced major challenges even finding usable data. “You have to be able to identify specific fields in a spatial data format, link that spatial data to each field’s pesticide-use rates, and also determine which fields are organic and which are conventional,” Powers explained. This information comes from several sources that can be tough to combine. What’s more, agricultural spatial data and pesticide use aren’t particularly well tracked, especially outside of California.
Fortunately, Larsen, Powers and co-author Frederik Noack, of the University of British Columbia, found one region that kept detailed records and made them publicly available: Kern County, California. As far as the authors were concerned, it was the golden ticket of the Golden State. “Kern County has annual spatial data for their agricultural fields that can be linked to the two other crucial datasets — pesticide use and organic-crop producer IDs — which is really rare,” Powers said.
This is only the latest pesticide research to come out of Larsen’s lab. She previously found that less diverse croplands led to greater variability in pesticide use, as well as higher peak pesticide application. And she hopes to extend this latest analysis beyond Kern County, to California as a whole. She, Noack and colleagues also have a project evaluating how the adoption of genetically modified crops impacts bird diversity in the U.S.
As many regions consider policy initiatives to increase organic cropland, it will be crucial to account for the spillover effects. Clustering organic fields could be an effective way to mitigate the unintended consequences organic farming has on pesticide use on conventional agriculture.
Daniel Long at University of Colorado Boulder contributed to this story.
JOURNAL
Science
ARTICLE TITLE
Spillover effects of organic agriculture on pesticide use on nearby fields
ARTICLE PUBLICATION DATE
22-Mar-2024
Organic fields increase pesticide use in nearby conventional fields, but reduce it in organic neighbors
AMERICAN ASSOCIATION FOR THE ADVANCEMENT OF SCIENCE (AAAS)
Expanding organic cropland can lead to increased pesticide use in surrounding conventional fields while reducing pesticide use on nearby organic fields, according to a study based in a leading U.S. crop-producing region. The findings provide insight into overlooked environmental impacts of organic agriculture and suggest that clustering organic fields could reduce pesticide use at the landscape scale. Organic agricultural practices are designed to have less negative local environmental impacts than other forms of intensive agriculture. However, the broader environmental and functional impacts of agricultural practices are only partially understood. By not using harmful chemical pesticides nor genetically modified seeds, organic cropland may function differently than conventionally managed fields, harboring more pest and beneficial species, or less. Some of these species may spill over into surrounding areas and affect pest control decisions for nearby fields. Using pesticide application data from nearly 100,000 observations from ~14,000 agricultural fields across Kern County, California – one of the leading crop-producing and pesticide-using counties in the U.S. – Ashley Larsen and colleagues evaluated how organic crop production influences pesticide use on surrounding organic and conventional fields. Larsen et al. found that organic fields can help reduce the use of pesticides in surrounding organic fields but increased their use in conventional fields. The level of pesticide use on conventional fields decreased the further away they were from nearby organic fields. By modeling the spatial configuration of different types of fields, the authors found that pests could be managed if organic and conventional fields were spatially segregated. When organic fields occupy a small share of acreage and are scattered across the landscape, expansion of organic farming increases overall pesticide use across the landscape. However, clustering organic fields close together lowers overall pesticide use on both organic and conventional farms by mitigating the spillover effects. Whether increasing pesticide use on conventional fields is due to spillover of pest species from organic fields or other farmer decision-making processes is unknown. “The analysis that Larsen et al. conducted documents how pesticide use can depend on the characteristics of neighboring farms, but it does not elucidate the mechanism that those patterns arise from,” writes Erik Lichtenberg in a related Perspective. “There is a continuing need for both ecological and economic fieldwork to elucidate the mechanisms at play.”
***A related embargoed news briefing was held at 11:00 a.m. U.S. ET on 19 March, as a Zoom Webinar. Video and audio recordings can be found here. The Science Advances paper mentioned during the Q&A is available here.***
JOURNAL
Science
ARTICLE TITLE
Spillover effects of organic agriculture on pesticide use on nearby fields
ARTICLE PUBLICATION DATE
22-Mar-2024
