Although orange peel shavings can be used to flavor foods and small doses of the oil from the orange peel is said to convey health benefits, large amounts of the oil can cause vomiting and nausea in humans. Such negative effects are even greater when the orange oil is used against insect pests. Orange oil can be deadly to many insects, including cockroaches, ants, dust mites, flies, wasps, spiders, crickets, and, perhaps most importantly, termites.
What Is Orange Oil?
Even though it smells strongly of citrus, orange oil is not fruit juice but is instead an extract from orange peels, a substance that is insoluble in water.
Orange Oil as a Termiticide
During the 1930s, California researchers began injecting arsenic into active infestations of dry wood termites, selecting it because termites not killed by the initial application usually succumbed to toxic residues. Arsenic was a very effective pesticide. But the toxic residue of a powerful poison also poses a notable danger to other animals, including humans, so alternative methods of combatting termites have long been sought. Today, orange oil as a natural product is increasingly marketed as a herbicide and insecticide, with particular effectiveness against dry wood termites. So, what is this wonder product and how does it kill termites?
The active ingredient of orange oil is d-limonene, a chemical known to be both a weed killer and an effective insecticide against a variety of pests, including flies, mosquitoes, ants, crickets, and mites. Scientists say that the oil dissolves the termite's exoskeleton, which destroys the insect's cell membranes and kills the bug due to massive losses of water and protein.
Inspect, Inject, and Inspect Again
The mode of treatment once a dry wood termite colony has been found is to drill holes into the infested wood and to inject the orange oil into the hollow spaces where the termites are feeding. The treatment works best if the insect galleries are identified and treated. Studies show that some residual effects continue in varying degrees from three days to three weeks after direct injection.
The majority of termites are killed by direct contact, and since orange oil deters the termites from feeding, some of them will then starve. After the treatment, the home or business owner should periodically check for signs of a new infestation. Trained termite-sniffing dogs have been very effective in sniffing out new or previously undetected termite colonies. Orange oil treatment is typically not preventative but must be applied each time a new infestation is discovered.
Limitations of Orange Oil as a Termiticide
There is an obvious appeal to using orange oil against dry wood termites since it is a much less toxic substance that the original arsenic used to combat the insects, or than the favorite modern chemicals, such as fipronil, imidacloprid, and hexaflumuron. But orange oil is not a do-all, end-all panacea against termites, and it has several drawbacks:
- Orange oil is not completely safe since it can cause stomach upset if ingested and irritation to skin.
- Its efficacy against termites is debated by some sources. For example, the Agriculture and Natural Resources, University of California states, "There are many localized [drywood termite] treatment methods available that include both chemical and nonchemical options. ... Botanical-based products (e.g., orange oil and neem oil) have been tried, but recent lab and field tests from two universities question the efficacy of at least d-limonene."
- While orange oil does seem to kill termites on contact, its residual effectiveness is minimal. Repeated applications are the norm when using orange oil.
- Termite galleries must be located and drilled into in order to inject the oil. Commercial fumigation, on the other hand, can kill termites throughout the house. The boreholes used to inject the oil can also leave a substantial amount of patching to be done.
The Bottom Line
As a minimally toxic pesticide, orange oil is worth trying as a solution against dry wood termites. But expect a somewhat lower level of effectiveness when compared to other commercial pesticides and pest control services, and be prepared for repeated applications as new infestations occur.
Raina, Ashok, et al. Effect of Orange Oil Extract on the Formosan Subterranean Termite (Isoptera: Rhinotermitidae). Journal of Economic Entomology, vol. 100, no. 3, 2007, pp. 880–885., doi:10.1093/jee/100.3.880
Drywood Termites, Agriculture and Natural Resources, University of California