The market for reduced-risk pesticides is thriving, mainly due to the fact that many conventional active ingredients – chlorpyrifos and diazinon – have been phased out of urban markets. This is because their widespread use in both agriculture and urban areas had led to increased exposures and unacceptable risks (FQPA 1996; NRC 1993; Wright et al. 1994). They were also a threat to water quality in many areas (Johnson 2004).
With this in mind, any natural, low-toxicity products that claim availability as pesticides are becoming increasingly popular. Orange oil is exactly that, and it also a by-product of orange juice processing, and is extracted from orange peels. Orange oil is currently available as an insecticide (Orange Guard™; ProCitra®) and as an herbicide (Green Match™). If all the claims are true, it is an effective natural product with low toxicity and no toxic residuals; a green product obtained by using waste.
Drywood termites are found along the southern border of the U.S., and they are major pests in both California and Florida. Given the impact of global warming their range is likely to extend northward (Quarles 2007). Treatment costs may exceed $500 million each year (Su and Scheffrahn 1990; Su and Scheffrahn 2000), so money saving potential new treatments are generating tremendous interest.
Drywood termites are not subterranean, they are either built into new structures (as they were already present in the wood beams utilized in construction,) or they invade by flying in from the outside. Detection is carried out by a trained and experienced inspector. Inspectors are limited to accessible areas and rely mostly on their eyes to find termite signs such as damaged wood, flying termites (swarmers), discarded wings and fecal pellets.
Local treatments include non-chemical methods such as heat, electrogun or microwaves or injections of chemicals directly into termite galleries. Whole house treatments may be either a heat treatment or a chemical fumigation, usually with sulfuryl fluoride (Vikane®).
Orange oil is a method of local treatment. When a drywood colony is found, holes are drilled into the infested wood, and orange oil is injected. Studies suggest that termites within a gallery will be killed by contact with orange oil, which relies on the holes and injections coinciding with the hollow spaces where termites are feeding.
Some orange oil manufacturers claim that orange oil 'wicks through wood', but there are no published studies that show that this is effective in killing termites.
Despite widespread publicity and promotion, very little has been published in peer reviewed journals on the efficacy of orange oil for termite control in real world situations. However, orange oil has been shown to kill termites by contact in laboratory situations. Dr. Rudolph Scheffrahn was hired by XT-2000 to test the efficacy of orange oil injections into infested trunks and branches of Brazilian pepper trees with active galleries of the drywood termites. Infested pieces were 82-144 cm long (32.8-57.6 in) and ranged from about 1-5 liters (approx. 1-5 quarts) in volume. Injections were made about every 5 inches (12.7cm). Termite mortality ranged from 48 to 100%. Lower mortalities were found in larger pieces of wood that had lower termite densities. Injection volumes of XT-2000 were about 3% of the total wood volume. Termites in control pieces injected with water showed no mortality (XT-2000).
With no published studies on orange oil field efficacy, we have to rely on call back estimates (Incidents where companies needed to reapply orange oil to exterminate the termites). According to Mike Folkins, owner of X-Termite, the company has treated 15,000 structures in the last nine years. The call back rate is 5-15% and Mike believes the success with orange oil depends on intensive structural inspections and extensive treatment of areas adjacent to active infestations.
According to Nathan Vogel of Orange-X Termite, his company has about a 5% callback rate from orange oil treatments. A major factor in keeping callbacks low is treatment of a large enough area so that all active drywood termite galleries are saturated with orange oil. Vogel believes termites are killed by contact, by fumigation action from orange oil vapors, and by eating the treated wood. Typically, about a gallon of orange oil is used in a local treatment.
Orange oil may indeed represent a low toxic, natural treatment for drywood termites that can compete with other local chemical injection techniques. The difficulty lies in the current lack of field or laboratory studies that directly compare orange oil efficiency with other available products for termite control. However, orange oil call backs do compare favorably against other options.
Orange oil provides another viable option for termite control and will particularly appeal to those searching for a “green option”. However, care must be taken not to risk damage to paint work as orange oil is also fairly flammable.
*Image courtesy of Dollar Photo Club
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