'Natural' Pest Control- Facts, Fiction, and Feasibility

​We’ve talked about ‘green’ pesticides before. Many ‘green’ pesticides contain one or more essential oils in their formulas. Although a number of studies report on the supposed efficacy of essential oils against insects, we see, comparatively, relatively few essential oil pesticide products on the shelf. Why? In this week’s blog, we’ll go over some of the pitfalls related to essential oil product development that have more to do with product development and less with political, legal, and personal stances on the ‘green’ pest management movement. However, for a commentary on those topics—check out our other blog post linked above!

Times Are Changing

Regardless of whether you agree with the practice, there is a very clear and increasing demand for products that consumers consider to be “natural”—especially when it comes to pesticides. A quick Google search for “natural pesticides” turns up more pages of results than we have time to navigate, as well as a number of blog posts (some from governmental entities) with DIY recipes for “alternative insecticides” that are, in theory, less harmful to the environment. Most of these recipes call for the use of essential oils. According to the National Institute of Environmental and Health Sciences, essential oils are “concentrated plant extracts that retain the natural smell and flavor of their source.” The use of natural products to control pests is not a new concept. Chrysanthemum flowers, which contain pyrethrins (an insect nerve toxin), were identified as insect-killers as early as 400 B.C. Their use is not outdated, either--we still use pyrethrins to control a number of urban pests. But, if you look at the history of pest management, there was a definite, clear shift toward the use of synthetic pesticides once they were developed. With increased use came increased scrutiny, however, and a number of negative environmental consequences related to synthetic insecticide use have been identified over time. Recent environmental movements have spurred the pendulum to swing back toward more natural compounds to protect pollinators, the soil, air and water quality, as well as human health.

Neem oil, sourced from the pressed fruits and seems of neem trees (Azadiractha indica) is becoming an increasingly common active ingredient in some pesticides, including those that target urban pests like bed bugs. (Image Credit: Thendral Muthusami, Image Source: Wikimedia Commons)

Limited 'Natural' Product Availability

​Essential oils and other related natural products are considered attractive alternatives to synthetic chemicals for insect pest management. The efficacy of many of these compounds has been demonstrated in peer-reviewed scientific studies. For example, mint oil can be repellent to fire ant workers and neem oil can kill bed bugs. But in spite of preliminary laboratory trial successes, there simply aren’t all that many EO products on the market. Why?
 
Authors of a recent study have identified a few issues with EO compounds that could be the limiting factors impacting commercialization of EO insecticides. First, EOs tend to have high volatility, meaning they evaporate pretty quickly. This allows EO compounds to serve as great fumigants, but, if a compound evaporates too quicky, it can impact efficacy. Evaporation of product means that there is no residual deposit left to kill insects that visit treated sites later. This is one of the main benefits of many synthetic products. If you have to re-apply EO products over and over to achieve the same result as a synthetic counterpart, labor and other tradeoffs may be unattractive to consumers or pesticide applicators.
 
Additionally, we still don’t completely understand how many of these EO compounds act against insects physiologically. Without understanding how these compounds work, it is difficult to start developing products that kill bugs in a consistent way. This may deter end users who want to know exactly how a product will perform in a given situation. For example, we know exactly where pyrethroid compounds act on insects and can explain their function clearly to end users. From product to product, they perform fairly similarly. We know how to rotate products when pyrethroid resistance to this synthetic active develops. EOs are much less predictable.
 
Finally, sourcing EOs can be exceptionally problematic. The cost of any given EO varies immensely depending on how oils are extracted and distilled from plants. Marketing can also be confusing. For instance, makers of “lemon eucalyptus oil” hint that this compound is the same as “oil of lemon eucalyptus”—but they certainly are not equivalent. Lemon eucalyptus oil is cheaper to produce and does not have the same mosquito repellent properties. These sort of mix ups make the EO product landscape confusing for consumers and difficult for manufacturers. Without organizational oversight and regulation, it is difficult for manufacturers to justify the high cost of production for quality oils when consumers often opt to purchase lesser quality product at a lower cost.
 
Currently, many EO products are exempt from FIFRA registration. Although this makes the registration process much faster and lower cost, it also means less oversight and an uneven competitive landscape. Until the registration model changes, including the adoption of more stringent efficacy testing requirements for EO products, we may continue to see a lack of innovation in this category from many pesticide manufacturers.

The published efficacy of some EO insecticidal products, like citronella candles, varies; yet, citronella candles are still sold for this purpose. More oversight in the EO pesticide market might lead to a more level playing field for manufacturers, and ultimately, more efficacious products. (Image Credit: Vilseskogen, Image Source: Flickr)

Conclusions

​EO products have potential to serve as novel, innovative compounds that can be used effectively in pest control. The efficacy of many of these compounds has been confirmed in laboratory trials. Yet, adoption of EO products by the pest management industry and widespread availability of effective natural compounds for consumer-based pest management is currently lacking. It would be wonderful if we had access to additional active ingredients to combat pest infestations. Hopefully, the issues highlighted here are addressed to allow for more proliferation of effective natural EO compounds that are equivalent (or close to equivalent) to their synthetic counterparts in the marketplace. This would allow manufacturers to meet the clear consumer demand for natural product alternatives, as well as the product effectiveness needed by pest management professionals whose livelihood depends on delivery of functional insecticides.

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