University of Wisconsin–Madison

Area Repellants

Many lanterns, coils, and candles reduce mosquito bites but plants don’t work.

Some mosquito control devices use repellents to protect a small area like a patio.  Devices that use allethrin or other pyrethroids to repel mosquitoes include the SC Johnson Off (TM) Mosquito Lantern, Mosquito coils, and the ThermaCell(TM) Mosquito Repellent System. 

A good study design for these devices requires sampling of mosquitoes that land on humans within the protected area and comparison of these results with another household without a device.  Additional information can be gathered by monitoring mosquito activity at the sites using simple light traps to verify that activity is similar between the two households.  Studies that have used this type of design indicate that area repellents emitting small doses of allethrin can reduce the number of biting mosquitoes (Collier et al. 2006, Jensen et al. 2000).

Geraniol candles protected much better than citronella candles

Candles or other devices emitting citronella have also been tested, but the results suggested relatively small reductions in the number of biting mosquitoes (Jensen et al. 2000, Muller et al. 2008, Lindsay et al. 1996).  Other plant essential oils (linalool and geraniol) in candles demonstrated better repellency rates in an indoor setting when close to the volunteer (Muller et al. 2008a).  In an outdoor setting,  geraniol candles gave moderate protection fo volunteers seated within a 1 meter distance from candles (Muller et al. 2008b).

Mosquito foggers, yard sprays, home misting systems

Insecticides can be applied to vegetation around homes for temporary reduction in biting pressure. Application can be through sprayers or foggers. One or two applications of insecticide during a season should not cause problems. These applications should be done by individuals who understand the risks associated and use proper protective clothing and technique during application. Although these chemicals will not provide permanent reduction of mosquitoes, they may temporarily reduce the populations to comfortable levels for an outdoor event.

However, mosquito biologists and other entomologists anticipate that too-frequent insecticide application by spray, fog or home misting systems will have adverse effects. In particular, dispensing pesticides at daily or weekly intervals, without using information about mosquito populations to determine whether application is needed, is simply bad practice. The following summary is slightly abbreviated from information provided by the American Mosquito Control Association, and describes the main issues with home-misting systems.
http://www.mosquito.org/news/

“The American Mosquito Control Association (AMCA) has a number of concerns with the sale of outdoor time-released insecticide misting systems to homeowners and businesses as a means to control mosquitoes. These systems utilize various synergized formulations of natural pyrethrins or synthetic pyrethroids that are dispensed into the environment at intervals determined by the user. Some systems also utilize minimum risk, FIFRA-exempt pesticides to control or repel mosquitoes.

We are concerned that application of pesticides through these misting systems will have several undesirable effects.

1. Unnecessary insecticide use. Users of these systems would not commonly have the resources to monitor the local mosquito species and density, or to evaluate the other parameters used to establish control thresholds in professional mosquito control operations. Thus, timed space sprays may result in needless insecticide applications, leading to increased costs to the consumer and potentially adverse environmental impacts.

2. Lack of efficacy data. Other than testimonials, an historically unreliable source, there is little to demonstrate that these systems actually serve to control mosquito populations even when using demonstrably toxic insecticides. Furthermore, other materials marketed for use in these systems such as cedarwood oil, garlic and other “natural” products by law do not have to prove their efficacy to any regulatory agency.

3. Non-target impacts. Timed-release sprays will negatively impact beneficial insect populations and other non-target organisms on site and through uncontrolled off-site drift.

4. Promotion of insecticide resistance. The indiscriminate application of pyrethrins will continually select for resistance to the whole pyrethroid class of mosquitocides, all of which utilize the same fundamental mode of action. The synthetic pyrethroids currently play an essential role in the mosquito adulticiding component of integrated mosquito management programs that manage resistance formulation through rotation of pesticides of different modes of action and other methods. The potential loss of these compounds from our suite of control methods, resulting from widespread development of resistance, would seriously compromise our capability to control adult mosquito populations responsible for disease transmission or severe annoyance.

5. Risk of pesticide exposure. It appears that safeguards to minimize the risk of direct contact with pesticide sprays by residents are lacking from many of these systems. Pyrethrins, though relatively safe compounds, bear the signal word “Caution” on the label, and the precautionary statements indicate that they may be harmful if inhaled. Labels also advise that pets and birds be removed and aquaria covered before spraying. Assuring homeowner compliance with these stipulations would be difficult, given that application of the pesticides is automated and can be overridden by the homeowner by means of wireless remote.

6. Incompatible with integrated pest management practices. The level of hands-off, automated control these systems promise may result in homeowners neglecting to use other methods to reduce local mosquito populations – even if encouraged by the installation technician. Practices such as removing mosquito larval habitats from the property or using personal repellents are essential to reducing human/mosquito contact. Neglecting these practices would, in turn, increase reliance upon the use of broadcast adulticides and propagate the unsound, one-dimensional approach to mosquito control these systems provide.

Until misting systems are reconfigured so that surveillance drives the application, efficacy is demonstrated and drift is minimized, AMCA believes they are not consistent with sound practices to promote public and environmental health and should be discouraged.

Citrosa plants have no effect

Even plants have been marketed as mosquito repellents.  Tests of the citrosa plant failed to demonstrate any reduction of mosquito bites in areas near the plant (Cilek et al. 1994, Cummins and Craig 1995, Matsuda et al. 1996).

 

References

Cilek, J. E. and E. T. Schreiber. 1994. Failure of the “mosquito plant” Pelargonium X citrosum ‘van Leenii’ to repel adult Aedes albopictus and Culex quinquefasciatus in Florida. Journal of the American Mosquito Control Association. 10(4): 473 – 476.

Collier B.W., Perich M.J., Boquin G.J., Harrington S.R., and Francis M.J.  2006.  Field evaluation of mosquito control devices on Southern Louisiana. Journal of the American Mosquito Control Association 22(3):444-450.

Cummings R.J. and Craig G.B., Jr.  1995.  The citrosa plant as a mosquito repellant?  Failure in field trials in upper Michigan.  The Vector Control Bulletin of the North Central States. 4: 16-28.

Jensen T., Lampman R., Slamecka M.C. and Novak R.J. 2000. Field efficacy of commercial antimosquito products in Illinois.  Jourrnal of the American Mosquito Control Association.  16:148-152.

Lindsay L. R.; Surgeoner G. A. ; Heal J. D. ; Gallivan G. J.  1996. Evaluation of the efficacy of 3% citronella candles and 5% citronella incense for protection against field populations of Aedes mosquitoes. Journal of the American Mosquito Control Association. 12:293-294.

Matsuda B. M., Surgeoner G.A., Heal J.D., Tucker A. O. and Maciarello M.J. 1996.  Essential oil analysis and field evaluation of the citrosa plant “Pelargonium citrosum” as a repellent against populations of Aedes mosquitoes.  Journal of the American Mosquito Control Association. 12:69-74.

Muller G.C., Junnila A., Kravchenko V.D., Revay E.E., Butler J., and Schlein Y. 2008a. Indoor protection against mosquito and sand fly bites: a comparison between citronella, linalool, and geraniol candles.

Muller G.C., Junnila A., Kravchenko V.D., Revay E.E., Butler J., Orlova O.B., Weiss R.W. and Schlein Y. 2008b. Ability of essential oil candles to repel biting insects in high and low biting pressure environments. Journal of the American Mosquito Control Association 24:154-160.