Green Pesticides

By Chris Williams on March 12, 2019.

Essential Oils (EO’s) as biologically active (bio pesticides) have potential great promise as effective alternatives to traditional synthetic pesticides. Many essential oils have been shown to have insecticidal, fumigant, antifeedant, attractive, or repellent activities (Mossa: J of Environmental Science and Technology May 2016)  There are 1000’s of these compounds that have been isolated and identified from 17,500 species of plants and about 300 are used commercially in the pharmaceutical, cosmetic/fragrance industries and many have now made their way into use as biopesticides.  About a dozen families of plants contain the highest numbers of these derivatives and two of the most common are Laminaceae  and Rutaceae, (mint and citrus respectively).  The chemistry of these compounds falls into many different classes, but the majority of them terpenes. About 90 percent of the terpenes found in these essential oils are known as monoterpenes and to further break down the classification of these organic alcohols into some more common terms, these are things like menthol, eugenol (clove oil) thymol (thyme oil) linalool (citrus oil) etc.  Now the very brief chemistry discussion is all well and good, but you’re probably asking, do they work? Are they safe? How is the performance?

The answer is yes, they do work.

Essential oils disrupt the insect’s physiology in several ways.  They act as neurotoxins primarily by blocking octopamine receptors and interfering with acetylcholinesterase to name a couple of effects.  They can also disrupt insect hormones and pheromones making them act as insect growth regulators.

Most of the essential oils are considered to be nontoxic to mammals with oral LD 50 values exceeding 5000mg/kg (rats) for the commercially available formulations. Their primary mode of action is in blocking octopamine receptors and these are not present in vertebrates. The performance of the available products is good and I’ve used Essentria iC3 for a couple of seasons now in super sensitive accounts with great results. There are some challenges to overcome however and that’s because essential oils are naturally volatile, soluble in water, and subject to oxidation, therefore limiting their residual life.  The good news is that newer formulations should be arriving soon using nanotechnology encapsulating the active ingredients in some type of polymer that will give effective, long lasting control on a wide variety of pests with unmatched safety. Stay tuned!

This research was cited as a reference for this article.



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