03
Apr
Study Bolsters the Case for Essential Oils (EO) in Organic Pest Management for Tomato Production
New research highlights the beneficial effects of rose essential oil (REO) on tomato plants as a plant defense potentiator (a substance or treatment enhancing natural defense mechanisms against pests, diseases, and other stressors by activating the plant’s own defense responses) for organic agriculture and horticulture. As reported in the Journal of Agricultural and Food Chemistry, REO, particularly its component β-citronellol, activates defense genes in tomato plants, enhances their natural defense mechanisms, and dramatically reduces leaf damage by 45.5%. Additionally, REO attracts beneficial insects that prey on herbivore pests. This study, “Novel Potential of Rose Essential Oil as a Powerful Plant Defense Potentiator,” adds to a growing area of scientific literature on essential oil (EO), largely unexplored as plant defense potentiators. Beyond Pesticides advocates for accelerating the switch from chemical-intensive agriculture to organic agriculture, which remains the only viable solution, in the long run, to address today’s existential crises by prioritizing natural pest control methods, soil health, and biodiversity conservation to protect farmworkers and consumers from the detrimental effects of petrochemical pesticide exposure.
Study Methods and Results
The researchers applied highly diluted solutions of EOs to the soil of potted tomato plants and assessed the expression levels of defense genes in the tomato leaves, such as PR1 and PIN2, which are known to play a role in plant defense responses. Additionally, they evaluated the extent of leaf damage caused by herbivores, including Spodoptera litura (a leaf eating pest) and Tetranychus urticae (spider mites), with field trials to validate the findings in a real-world agricultural setting. The researchers treated the soil of tomato plants with REO solution over three weeks and compared the pest damage level to plants treated with a control solvent. This field trial aimed to assess the practical effectiveness of REO in enhancing plant defense against pests and attracting beneficial arthropods.
The main findings of the study include:
- REO, particularly β-citronellol, activates defense genes, including PR1 and PIN2, in tomato plants, which enhance their natural defense mechanisms;
- Tomato plants treated with REO show significant reductions in leaf damage caused by herbivores, such as Spodoptera litura and Tetranychus urticae, compared to plants treated with a control solvent.
- Field trials confirm the efficacy of REO in enhancing plant defense in real-world agricultural conditions, resulting in a remarkable reduction (45.5%) in pest damage to tomato plants.
- REO attracts herbivore predators, such as the Phytoseiulus persimilis mite, while not repelling the spider mite herbivores themselves.
A specific concentration of REO (1 × 10^5 dilution), identified as optimal, echoes findings similar to those for valine menthyl ester, another plant defense potentiator, suggesting that higher doses might be detrimental, while the precise dilution used showed no negative impact on plant fitness. Additionally, the study finds that soil application of REO was the only effective method for enhancing plant defense, as direct leaf application proved ineffectual—potentially due to the volatile nature of EOs and rapid evaporation when applied to foliage. Consideration in future research designs to calibrate and test for optimal concentrations and application methods (soil and foliar) across different environmental conditions is key to understanding how EOs or their derivatives might be systematically distributed within plants to enhance defense mechanisms even more effectively.
The study underscores EO’s enormous potential as a safer and more effective tool of pest management—compatible with organic agriculture and horticulture—while minimizing health and environmental risks, an approach supported by Beyond Pesticides. Containing compounds with potent insecticidal and repellent properties, EOs have an “exceptional safety profile…(with) a range of bioactivities that greatly benefit human health.” EOs are a promising tool against the relentless issue of resistance. Conventional agriculture and the pesticide industry respond to weed resistance, for example, with a pesticides arms race, introducing more toxics as a solution that perpetuates the problem. Apart from the toxicity and other “downstream” issues related to many synthetic control chemicals, all organisms will eventually develop resistance against the harmful substances to which they are chronically exposed. For more information, please see Beyond Pesticides’ previous coverage here.
Mosquito Management and EOs
As noted in the March 24, 2022, Daily News post analyzing the study “Larvicidal and adulticidal effects of some Egyptian oils against Culex pipiens,” published in Nature, various EOs show significant larvicidal and adulticidal activity against the common house mosquito, Culex pipiens, which is a vector for diseases like West Nile virus and Saint Louis encephalitis. Egyptian scientists tested 32 EOs on C. pipiens larvae and adults, identifying garlic, dill, tea plant, fennel, fennel flower, sage, garden thyme, and sweet violet as highly effective, achieving up to 100% mortality. In addition, a 2019 study in the Florida Journal of Mosquito Control, found EO-based sprays more effective than common synthetic alternatives, supporting a science-based mosquito management approach that prioritizes preventive measures and ecological considerations while advocating for the use of less toxic, biodegradable products like EOs, based on monitoring data to minimize risks to non-target species. As communities like Boulder, Colorado, lead by example, in limiting biological larvicides in favor of ecological methods to control mosquito populations, it is vital to emphasize that even the least-toxic adulticides should be viewed as a mechanism of last resort, used under strict conditions to prevent mosquito-borne disease risks.
Solution in Organic Methods
EOs and other nature-based pest control alternatives offer a beacon of hope amidst the escalating crises wrought by conventional chemical-intensive agriculture. Beyond Pesticides calls for an end to the use of petrochemical pesticides and fertilizers by 2032 to safeguard human health, biodiversity, and environmental integrity. Embracing organic practices means embracing a holistic approach that nurtures the soil, promotes natural pest control mechanisms, and fosters resilient ecosystems. These ecological practices can mitigate adverse health risks associated with exposures and address the root causes of environmental degradation and climate change detrimentally impacted by petrochemical pesticides.
By calling for a systemic shift to organic land management practices through advocacy, education, and grassroots action, Beyond Pesticides continues to lead the charge in catalyzing this transformation. In the introduction of our 2023 Transformative Change report referencing the vital need for a transformation to land and building management systems that align with nature, Jay Feldman, executive director of Beyond Pesticides, writes, “The transformative solution is a partnership with nature, practices that have been adopted in organic systems. With this approach, we honor all organisms who play a role in ecological systems on which life depends, and we seek the rapid adoption of those practices and materials that are already available to us or can be incentivized to become widely available quickly.” The fundamental solution lies in transitioning from conventional chemical farming to organic, regenerative agriculture.
For more information, please refer to the Organic Agriculture page on our website. In addition, Beyond Pesticides’ ManageSafe™ | Least Toxic Control of Pests in the Home and Garden database is an excellent resource for safer solutions for readers. To learn about pesticides that may be used in local communities, please see Beyond Pesticides Gateway on Pesticide Hazards and Safe Pest Management. If you have a concern about pesticide use in your community, please contact Beyond Pesticides’ info desk at [email protected].
All unattributed positions and opinions in this piece are those of Beyond Pesticides.
Sources:
Novel Potential of Rose Essential Oil as a Powerful Plant Defense Potentiator, Eiki Kaneko, Kenji Matsui, Journal of Agricultural and Food Chemistry, 2024
Products Compatible with Organic Landscape Management, Pesticides and You, Spring 2017
Pesticides and Soil Health, Friends of the Earth, 2019
Essential Oils In Organic Agriculture: A Review Of Practices And Potential, Natural Volatiles and Essential Oils, 2021
Biocontrol Potential of Essential Oils in Organic Horticulture Systems: From Farm to Fork. Frontiers in Nutrition, 2022
A Note on Biopesticides and EPA Definition
“Biopesticides”—widely regarded as an alternative to chemical pesticides and hence given a special status in U.S. Environmental Protection Agency (EPA) regulation—need a better definition. Essential oils are one example of biopesticides naturally occurring substances that control pests (biochemical pesticides), microorganisms that control pests (microbial pesticides). However, Beyond Pesticides has argued that the current EPA definition for “biopesticides” is deceptive and misleading because it includes genetically modified organisms or synthetic analogs of naturally occurring biochemicals. The development and adoption of genetically engineered (GE) and other questionable synthetic biopesticides can be seen as a diversion from the necessary shift towards sustainable food production. (See Beyond Pesticides call to action here).
