Writer: Natasha Matta
Commercial organic pesticides that combat the bacteria that grows on mulberry leaves, such as pyrethrins (chrysanthemum-based pesticides) or copper-based pesticides, often have adverse health effects on silkworms and decrease silk quality. Thus, our team proposes a novel solution using the active ingredients of clove and thyme (eugenol and thymol) to synthesize an organic pesticide that kills the bacterial blight (Pseudomonas syringae) that harms mulberry leaves (the silkworms’ sole food source) without having a negative impact on the health of silkworms that come into contact with it or the quality of the silk that those silkworms produce.
Current treatments for bacterial blight include aforementioned crop rotation, changing the crop grown in a field every few months, and use of organic and non-organic bactericides and fungicides. Organic pesticides are often preferred over non-organic as they are conventionally viewed as healthier and safer. However, organic pesticides like pyrethrins and copper-based pesticides can be just as toxic to plants and animals as non-organic alternatives.
However, low concentrations of essential oils from clove buds and thyme have been shown to be successful in inhibiting the growth of Pseudomonas syringae. Essential oils can be extracted from the stem, flowers, seeds, bark, or other parts of the plant, and they serve as a natural but effective way to kill bacteria or repel pests like insects or wasps from crops because of their strong smell and properties. Essential oils can also be used as an additive for animal feed because they provide nutrients but do not pose the same dangers of commercial antibiotics used in animal husbandry (breeding and raising animals). Both clove and thymol have antimicrobial properties, and clove can aid in digestion during the gestational period. Thyme-based spray pesticides are commonly used across the world, primarily in Florida, North Carolina, and countries in South America. Thus, organic pesticides made from eugenol and thymol, the active ingredients of clove and thyme, are a safer alternative to toxic pyrethrins, which use chrysanthemum, and copper-based pesticides that interfere with the gastrointestinal tract and lead to acute toxicity in silkworms with repeated exposure. Additionally, clove may actually aid in protecting silkworms from infection and improve their intestinal health. Those who work in agriculture industries often fall victim to asthma and various lung diseases because they breathe in pesticide nearly everyday. However, clove and thyme essential oils are often used as a form of aromatherapy that has been found safe and even beneficial for humans to breathe in. Repeated exposure to a pesticide derived from eugenol and thymol would be much safer than to the organic pesticides currently on the market.
We propose a simple and cost-effective method to extract eugenol from clove and thymol for thyme: agitating 500g of ground clove or ground thyme respectively in 300 mL of solvent 99% methanol at 50°C for 2 hours, filtering the mixture through a cheesecloth, and diluting it with water. The expected yield for this method of extraction for 1g of clove powder is 0.18g of essential oil, which is approximately 89% eugenol. Sericulture farmers can perform this procedure with minimal training, low cost (clove and thyme powder, methanol, and a cheesecloth), and even from home, circumventing the factory processing, expensive machinery, and labor cost that contributes to the increased cost of commercial pesticides. However, this pesticide can also be produced on a larger scale with ground clove and ground thyme in bulk amounts and stronger machinery to quickly filter a larger amount of the mixture. A simple and less expensive but safer and more effective pesticide could kill the Pseudomonas syringae that kills or stunts the growth of mulberry leaves, improve silkworm health and the health of the workers who are exposed to it and end up breathing it in on a regular basis, yield larger amounts of silk as well as higher quality silk, and drastically increase profits, making the already multi-billion dollar sericulture industry even more lucrative and safer for the millions of people it employs globally from the sericulture farmers who raise the silkworms to those that weave the silk for commercial use.
After establishing the insufficiencies with current methods, the writer introduces a novel method of synthesizing an organic pesticide that combats bacterial blight on mulberry leaves, a widespread problem within sericulture, but does not have the adverse effects on silkworm health and silk quality of the organic pesticides currently on the market. She “debunks” or points out the flaws with common misconceptions like the idea that organic pesticides are always safer than nonorganic alternatives and uses examples of organic pesticides, pyrethrins and copper-based pesticides that have been found to be harmful to silkworms. She also addresses the problem of rampant lung disease and asthma in the agriculture industry because of repeated exposure of farmers to pesticides that can be toxic to humans and how clove and thyme would not have those same drawbacks. The sericulture industry employs millions worldwide from suppliers to farmers to silk weavers, who are all exposed to dangerous pesticides at their different level in the production change, so implementing a new safer way of combating bacterial blight on mulberry leaves would improve the health of all that are exposed to the silkworms or silk that they produce. One way to make this part of the argument more compelling would be to include statistics on the prevalence of lung conditions in the agriculture industry or impaired health in the sericulture industry more specifically. However, the writer establishes the context of the issue, how the sericulture industry not only generates billions of dollars annually but also provides jobs for millions at all levels of production. The author suggests a simple and cost-effective method of extracting the pesticide from clove and thyme powder that is actually more efficient, found to be effective on Pseudomonas syringae through empirical research, and can be produced on a small scale for local sericulture farmers or on a large industrial scale. Her work is not based on conjecture but backed by research, which she cites. The author used reputable sources including research papers from peer-reviewed science journals and wrote professionally, using third person and employing correct spelling, grammar, and formatting.
Characteristics of Pseudomonas syringae pv. mori, Causal Agent of Bacterial Blight of Mulberry (Morus Spp.) in Indonesia, https://link.springer.com/chapter/10.1007/978-94-011-5472-7_100
Essential Oils with Inhibitory Capacities on Pseudomonas syringae pv. actinidiae, https://scialert.net/fulltext/?doi=ajppaj.2018.16.26
Acute Toxicity of Organophosphorus and Pyrethroid Insecticides to Bombyx mori, https://www.researchgate.net/publication/5394388_Acute_Toxicity_of_Organophosphorus_and_Pyrethroid_Insecticides_to_Bombyx_moriI
Studies on the Toxicity of Copper to the Silkworm, Bombyx mori, https://pdfs.semanticscholar.org/7e1e/b6b54f89581a63f017cb4e19cb5e1200da5c.pdf
Midgut Immune Responses Induced by Bacterial Infection in the Silkworm, https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4609539/
Separation and identification of eugenol in ethanol extract of cloves by reversed-phase high-performance liquid chromatography, https://link.springer.com/article/10.1007/BF02540996
Benefits of Using Clove Oil in Animal Husbandry, https://www.essentialnaturaloils.com/benefits-of-using-clove-oil-in-animal-husbandry#:~:text=Essential%20oils%20like%20clove%20oil,other%20parts%20of%20the%20plants.
Why Thyme Oil is Becoming Popular in the Agricultural Industry, https://www.essentialnaturaloils.com/why-thyme-oil-is-becoming-popular-in-the-agricultural-industry