Orange Oil for Termites

Orange oil is something that is extracted from peels from oranges. It is mainly made up of a chemical called d-limonene, which is a natural insecticide. This is toxic to insects, but has a very low toxicity to mammals. A lot of companies have started promoting it as a natural way to get rid of termites - they will inject orange oil into the wood of your house, and use it as an alternative to fumigation (since you don't have to move out to do it). The current answer in my opinion is that orange oil could be useful when combined with other methods - but I wouldn't rely on it as the sole way to try to kill them off.
Orange oil does kill termites on contact. However, it's a questionable remedy for actually getting rid of a colony. There have been no published studies proving that it's effective as a termite remedy. One of the things people are concerned about is that it is organic and tends to lose its effectiveness rapidly - unlike many pesticides, it can't just sit there for a year and keep killing insects. If you don't get the entire colony in one go (and kill the queen), they'll be back. And that's hard to do because they don't all live in the wood. With subterranean termites (the most common type) they live underground as well.

Study by Nicholls State University Professors

This study published in the Journal of Economic Entomology showed that orange oil was highly effective if you stuck a bunch of termites into a container with it. But if you actually put it into a model of a wall, it killed very few of them. It was even less effective in the ground, because it was basically gone after three weeks.

Study by University of California - Riverside Professors

This study, by two professors at the University of California - Riverside (Michael Rust and Jody Venturina) looked at the effectiveness an orange oil based product called XT-2000 (you can read it here). They tested it on drywood termites, and found that it was "extremely toxic" to them - but only for short periods of time. This is because the deaths are caused by vapors, which lose their ability to kill them after 24 - 48 hours. They did find that even though it stops killing termites at that stage, it does prevent them from feeding off the treated wood, which can eventually cause the termites to starve to death if they have no other food source. However, it wasn't as effective as several other products they tested. The difficulty I see based on this study is that you basically need 100% treatment of the wood in your house. If they can find anything that isn't treated, they'll eat it and be able to survive - and it stops killing them after 24 hours or so.

Does using orange oil make my house more likely to catch fire?

I haven't been able to find a definitive answer to this question. I e-mailed Michael Rust, a professor of entomology at the University of California - Riverside. He's done some studies with orange oil, and he was gracious enough to take the time to respond that: "Like most oils it will burn. If you put a wick in the orange oil, it will burn very nicely. I don't know if it makes the treated wood more flammable." There's also an Australian expert named "Dr. Don" who notes he has used it to start fires and says he would hesitate to use it.

Another website called the Termite Guy believes it's a significant risk, calling it "glorified organic lighter fluid" and compares using it to soaking your home in gasoline. I also found this video from a company called Hi Tech Termite Control showing a model house being lit on fire using just orange oil. They also talk about some anecdotal situations where they say fires were caused by it. I think you do have to take what they're saying with a grain of salt - they are competitors trying to sell you their own products, after all.

One of the companies that sells it (a brand called XT-2000) says their orange oil is "combustible" and less likely to cause fires than other products called "flammable," but doesn't really speak to its safety. I've seen a similar statement on several other pages from companies that sell it. Again, this is from an interested party. One thing that worries me personally a little is that they don't just come out and say "no, it doesn't start fires." When a company has very specific language like that about their product (that doesn't really answer the question), often they don't want to give you the straight answer for a reason.

The end verdict is - I don't know whether your risk of a fire goes up by using orange oil. It can definitely catch fire - but so can wood. I haven't been able to find any tests, studies, or comments from unbiased experts that would give a definitive answer one way or another.  

If you have a question about termites you want answered, submit it here.

Sources and Useful Links:

http://en.wikipedia.org/wiki/Orange_oil

http://www.redding.com/news/2007/dec/01/pass-on-orange-oil-for-termites/

http://www.ars.usda.gov/research/publications/publications.htm?seq_no_115=203141

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