Researchers at Rutgers University and the USDA’s Agricultural Research Service tested a variety of essential oils, silicone oils, and paraffin oils for their toxicity to the common bed bug (Cimex lectularius) and found the silicone and paraffin oils to be most effective. (Photo credit: Changlu Wang, Ph.D., Chen Zha, and Andrew Li, Ph.D.)

By Andrew Porterfield

Could the answer to a burgeoning bed bug problem come from another popular trend, essential oils? Not from most oils, say researchers from Rutgers University and the USDA’s Agricultural Research Service, though a few oils—particularly silicone and paraffin oils—show some potential.

Over the past 10 years, the common bed bug (Cimex lectularius) and tropical bed bug (C. hemipterus) have surged in population, resulting in infestations in homes, hotels, and other institutions (such as assisted living facilities) throughout the United States. The tropical bed bug was recently discovered in Florida after a 60-year absence.

Residential use of retail, non-professional applications of pyrethrin or pyrethroid insecticides and professional applications like imidacloprid, deltamethrin, and cyhalothrin have constituted the mainstay of defenses against bed bugs. However, resistance of bed bugs to pyrethrins and pyrethroids is well documented, and professional insecticides have run into biological resistance as well as resistance from members of the public concerned about health and environmental effects of these insecticides.

At the same time, essential oil products have become more popular recently, for their sensory properties and alleged connections to a wide variety of health issues. Many “green pesticides” based on these essential oils have been developed over the years, as well. Many of these products are exempt from regulations under the U.S. Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA), so manufacturers do not need to pay for or take the time to register them with the U.S. Environmental Protection Agency (EPA). However, a number of these oils have been shown to be ineffective against insects, little data exists about the range of effectiveness of this wide variety of oils, and no studies have looked at their specific toxicities against bed bugs.

Changlu Wang, Ph.D., and Chen Zha, entomologists at Rutgers University in New Jersey and Andrew Li, Ph.D., entomologist at the USDA-Agricultural Research Service, tested 18 essential oils, three silicone oils, and paraffin oil and found that only silicone and paraffin oils showed any effectiveness against bed bugs. However, silicone and paraffin oils did indeed show mortality rates significant enough to rate them as a potential alternative bed bug control. Their results were published today in the Journal of Economic Entomology.

The researchers collected bed bugs from an apartment building in Indiana and conducted four experiments.

1. The first screened 18 essential oils, three silicone oils, and one paraffin oil using a topical assay, while control bed bugs were treated with acetone. The bed bugs were observed up to 14 days after treatment.
2. The second experiment took three oils: blood orange, paraffin, and silicone oil 1, which showed the greatest effectiveness in the first experiment. Here, oils were diluted to determine lethal dosages of each.
3. The third experiment compared different cedarwood essential oils, geraniol, and EcoRaider (a commercial product consisting of cedarwood oil and geraniol), to see if origin and sources of plants had any impact on essential oil efficacy.
4. In the fourth experiment, the scientists tested a silicone-oil-and-water solution (with the only silicone oil tested that could be mixed in water without surfactants).

Of the oils tested, blood orange oil had the highest mortality ranking for essential oils. The silicone oils and paraffin oil had the highest mean rankings among all the oils tested. The researchers noticed significant variation among bed bug mortalities, from 5 percent for spearmint oil to 100 percent for silicone oil 1 (dodecamethylpentasiloxane). Lethal doses (LD50) of the top oils were 0.184 milligrams per bed bug for blood orange, 0.069 milligrams per bed bug for paraffin oil, and 0.038 milligrams per bed bug for silicone oil 1.

All the oils showed some toxicity toward the bed bugs, but toxicity varied a great deal according to oil type, origin, and source plants. Efficacy of oils with the same name from different sources or manufacturers can vary a great deal, too, the researchers noted. Paraffin and silicone oils have some other advantages to essential oils as insecticides, because they are odorless and colorless, and may act as safe alternative methods for bed bug management.

“The differences in toxicity might be due to the chemical structures of the major components in the chemicals. Silicone and paraffin oil may more likely suffocate the insects by preventing them from breathing,” Wang, who is known for his work on novel ways to control bed bugs, said in an interview.

So far, though, the oils have an additional advantage over traditional pesticides: no resistance. “So far there are no reports of resistance to these oils,” Wang said. “It is very difficult for insects to develop resistance to them since they are not neurotoxins.”

Andrew Porterfield

Andrew Porterfield is a writer, editor, and communications consultant for academic institutions, companies, and nonprofits in the life sciences. He writes frequently about agriculture issues for the Genetic Literacy Project. He is based in Camarillo, California. Follow him on Twitter at @AMPorterfield or visit his Facebook page.