Crop & Pest Report


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Insect Repellents - What Works (5/26/11)

Ticks, black flies and mosquitoes are active and ready to dine on you! So, if you plan to spend some time outside, it is good to take some general precautions to prevent their itchy bites and discomfort. Ticks and mosquitoes also can transmit diseases to humans.

For example, ticks can transmit Rocky Mountain spotted fever and Lyme disease, and mosquitoes can transmit West Nile virus. The main question consumers have is how to find a product that can prevent you from being bitten and is safe to use. Mosquitoes and ticks are attracted to us by our odors and carbon dioxide from breathing. Most repellents work by masking the chemical cues and making you unattractive for feeding. Unfortunately, they only work at a short distance and do not kill their insect target. So, even when you have repellent on, you can still see mosquitoes whining in your ear and flying around nearby. Repellents are available as sprays, wipes, sticks, foams and lotions. It is important to select the ‘right’ repellent for your activity (exercising or relaxing), weather (hot and humid, or cool and dry), and the amount of time that you plan to be outdoors. The EPA has a website to help you choose the repellent product that is right for you at:

Female mosquito taking a blood meal

Some popular repellents are: DEET (or N,N-diethyl-m-toluamidae or N,N-diemethylbenzamide), Picaridin (KBR 3023), oil of lemon eucalyptus, and IR3535. DEET and Picaridin are both synthetic repellents, whereas oil of lemon eucalyptus and IR3535 are biopesticide repellents (derived from natural materials). In general, the more active ingredient in a repellent corresponds to a longer period of protection from bites. However, shorter protection time does not necessarily mean less protection, just less time. In Table 1, the protection times of tested mosquito’s repellents are listed and range from 5 hours to 0 (Source: University of Florida, IFAS Extension). When using repellent, apply enough to cover exposed skin or clothing. Avoid apply repellent to skin under the clothing and to cuts, wounds or irritated skin. Some people may be allergic to ingredients in the repellent. Use common sense when applying products and read the label first! The EPA has ruled that normal use of DEET is not a human health concern.

Besides repellents, clothing is important and netting can be used to deter biting insects, such as mosquitoes. Some outdoor manufacturers, such as L.L Bean, also make “Buzz Off” clothing with Permanone-treated fabric as an alternative to topical repellents. Permethrin is the active ingredient in Permanone, which is safe for humans according to the EPA. Buzz Off clothing is effective in repelling insect for 25 washings. 

Other common topical products on the market combines repellents and sunscreen. However, the Center of Disease Control (CDC) does not recommend using combined products with both repellent and sunscreen. Blending these two products decrease their efficacy due to lower amounts of active ingredients. Also, this may increase your exposure to the insect repellent since you may need to reapply more frequently. The CDC recommends applying sunscreen first and then the insect repellent.

There are several devices that don’t work as bug repellents, such as devices that emit sound to repel mosquitoes or ticks. Eating garlic, vitamin-B, onions or any other foods will not make a person less attractive to mosquitoes either. Don’t use traditional electric bug zappers. They attract many other insects, often beneficial insects, but mosquitoes largely ignore them. The newer portable traps (Mosquito Deleto from Coleman Company or Mosquito Magnet from American Biophysics Corp.) emit carbon dioxide and a chemical called octenol, which lures mosquitoes away from people. However, it is unknown whether these traps reduce the number of bites to people nearby. Citronella candles have been used since 1882 to repel mosquitoes, but research has shown that they are no more effective than plain candles, which give off heat, carbon dioxide and moisture.

Mosquito repellent table

Proper and safe use of insect repellent will help make your summers more enjoyable when working or playing outdoors!

 Janet J. Knodel

Extension Entomologist

This site is supported in part by the Crop Protection and Pest Management Program [grant no. 2017-70006-27144/accession 1013592] from the USDA National Institute of Food and Agriculture. Any opinions, findings, conclusions, or recommendations expressed are those of the website author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture.

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