Herbs vs. Bugs

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Some other herbs indicated in the scientific literature as having tick-repellent qualities include rose geranium, rosemary and California laurel. Further testing is warranted.

Other Critters

When I had an office in a cockroach-infested lab in New Jersey, my favorite nontoxic control was a large jar filled with banana skins, fried pork rinds and other food scraps. I greased the inside edge of the mouth with Vaseline and then placed a small ramp leading up to it. Cockroaches used to literally “walk the plank”, fall in and never get out. I did not know it then, but scientific studies have documented what housewives have always known: that beef broth and oils of banana, sweet orange, apple and pineapple are good attractants for cockroaches. In this case, attracting them accomplishes the same end as repelling them. This type of trap can be effective in the home, particularly in relatively moist places such as under the sink.

If your grandma put bay leaves in her flour canisters, it was because of this herb’s long reputation as an insect repellent. Today, the effectiveness of bay (Laurus nobilis) in repelling cockroaches is well documented. Simply place fresh or dried bay leaves in and around cupboards, especially where they will be brushed and crushed in normal kitchen activity. I use and recommend bay leaf as a cockroach deterrent. Other plants shown to be repellent to cockroaches include Osage orange (Maclura pomifera), Japanese peppermint (Mentha canadensis), Scotch spearmint (M. gracilis) and vetiver.

Anyone who has had a child come home from school with head lice knows the horror of these creepy-crawlies. You wash everyone’s hair, wash all clothing and disinfect the furniture, but that doesn’t stop you from scratching your own head for days on end. Many shampoos contain natural pyrethrins, which do indeed kill the adults, but the eggs, or nits, are usually not affected. Some plants that have shown effectiveness against lice include tomato, rosemary and marsh tea.

What Doesn’t Work

Lemongrass (Cymbopogon citratus) as an applied oil is a poor repellent against both mosquitoes and flies. Likewise, eucalyptus (Eucalyptus globulus) has been shown repeatedly to be ineffective against mosquitoes and flies despite its long use for that purpose in both homemade and commercial preparations. Pterigeron bubakii, a plant that Australian aborigines use to repel fleas, has also proven ineffective in the laboratory.

Ads in the popular press during the past few years have ballyhooed Citrosa or Van Leenii geranium as repelling mosquitoes just by sitting on the patio. I’m sorry to say that scientists have not been able to confirm this claim. If Citrosa leaves are crushed, they exhibit 30 to 40 percent of the repellency of DEET formulations, but crushed lemon thyme (Thymus ¥ citriodorus) has 62 percent repellency. Your money would be more wisely spent on lemon thyme, but in those tropical areas where lemon thyme fails, then crushed Citrosa geranium may offer some benefits.

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