JULY
2009

 

By
Tom Turpin
 
Professor of
Entomology
Purdue University

 

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07-09-09

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Can Products in Pantry Help Avoid Insect Bites?

One of the realities of life is that encounters with insects of the biting kind always increase during the summer. When an insect takes a bite out of a human, scientists say it is an example of an ecological relationship called parasitism. Such a relationship means that one species will benefit and the other will not.

In the case of insects, biting us it is painfully evident that we are not the species benefiting from the encounter. So thinking animals that we are, we do what we can to avoid becoming a two-legged meal for a six-legged insect.

Our efforts to avoid providing food for an insect are generally associated with one of three approaches. The first, at least in modern times, is use of an insecticide to kill potential offending insects. Some of these efforts utilize area-wide programs involving governmental units such as mosquito abatement districts.

The second general approach is directed toward keeping the insects out of our spaces. Such things and activities, including window screens, mosquito nets, light traps, ultrasonic devices and burning plant materials, are used. In spite of the claims touted through slick ads in the media, only the physical barriers - the screens and the nets - and burning some plant materials actually work. Light traps and ultrasonic devices when used alone are not effective in reducing encounters of the close kind with biting insects.

A third approach can best be described as personal protection that involves the use of an insect repellent. The idea behind repellents is that a person wears a chemical that either masks an odor that attracts the insect in the first place or one that prevents an insect from landing.

Through the magic of modern chemistry, a number of very effective insect repellents are available on the market. The first was DEET, developed in 1946 by the U.S. Department of Defense. Others include picaridin, IR3535, DEPA and MGK 264. All of these products have abbreviations because the official chemical names are impossible to pronounce or remember unless you happen to be a chemist, who uses long hyphenated chemical names on a daily basis.

The first repellents, though, were natural compounds that were no doubt discovered by accident. Which brings us to the relationship between humans and plants. Plants are a great food item. If you need further support for that statement just ask any vegetarian. Because plants have been fed on by all kinds of creatures over the ages, these green food items defend themselves with chemical defenses. In other words, many plants are bad tasting or even poisonous when eaten.

And as you might suspect, many plants produce chemicals that insects avoid, and some of these have become what are called natural repellents. For instance, oil of citronella, a product made from a grass of Indian origin, first sold as a repellent in 1882 as McKesson's Oil.

As it turns out, many plant extracts that are used as spices and flavors in cooking have some insect repellent activity. For instance, anise, basil, fennel, garlic, ginger, peppermint, spearmint, black pepper, rosemary, sassafras, sesame, bayberry and turmeric will all provide short duration relief from biting insects.

Plant extracts that have a longer protective action include celery, clove, coconut oil, garlic, lime, palm oil, soybean oil and thyme. In general, these natural products are highly volatile and evaporate from the skin rather quickly. That means that the products will have to be reapplied often to be effective.

The general perception that natural products will be safe to eat or rub on our skin is not always true. We need to remember that nicotine, cocaine and strychnine are natural plant products, as is urushiol, the problem chemical in poison ivy. And the widely used citronella, for instance, can cause irritation in some people when applied on the skin.

So this year when mosquitoes begin to bite as you work in the garden, don't reach for the repellent spray can. Just head to the pantry and grab a little soybean oil and add a dash of rosemary and thyme and a pinch of black pepper. If the homemade mixture prevents bites, you won't be sure if the mosquitoes were repelled or if they just mistook you for a garden plant!

 

Writer: Tom Turpin
Editor: Olivia Maddox