|This story has been corrected.|
When Nancy Liedke saw recent reports about a soap-and-water "mixture" being used to fight mosquitoes, she had to wonder how it could be so simple.
"What’s a mixture? One cup each?" she asked.
Liedke, a retired Health Department worker and teacher from Kailua, had found her own recipe for fighting mosquitoes in a magazine.
"It’s called an all-round disease defense tonic," she said.
Though she laughs at the name, Liedke said it has been effective against mosquitoes, whose eggs develop into larvae and hatch in standing warm water, and other insects in her garden.
The recipe: Mix together 1 cup of chamomile tea, 1 teaspoon of liquid dish soap, a half-teaspoon of vegetable oil, a half-teaspoon of peppermint oil and 1 gallon of warm water. Pour the mixture into a sprayer and apply to plants every week until "really hot weather."
Liedke sprays her concoction underneath the leaves, on the soil surrounding the plant and in the water that accumulates in saucers under potted plants.
"I’ve used it for quite a while," she said. "I haven’t lost many plants to it."
Liedke has a particular interest in the recent cluster of dengue fever cases in Pearl City that prompted the latest attempts at mosquito control. She thinks she came down with dengue shortly after moving here in the 1960s.
"My bones ached and my eyes were just awful," she said. Her doctor later suggested the malady was the mosquito-borne dengue fever.
Hi‘iaka’s Healing Herb Garden
Neem Trees of Hawaii
Dengue fever information
THE STATE Health Department suggests a much simpler recipe for fighting mosquitos: 1 tablespoon of detergent to 1 gallon of water. Sprayed on plants, it creates a film that effectively suffocates mosquito larvae. But even that recommendation comes with a caveat.
"There are very few studies done on soap, especially out in the environment," said Peter Oshiro, program manager at the state’s Vector Control Branch. "Depending on rain and whatever conditions, it may dissipate pretty fast. It’s good as a temporary measure as you’re constantly monitoring the area for mosquitoes."
A long-term solution to a mosquito or insect problem would be to grow a neem tree, an Indian tree that is a natural killer of mosquitoes and other insects. The tree and its byproducts, including leaves and seedlings, are sold commercially by Neem Trees of Hawaii, based in Waimanalo.
Co-owner Hank Liljedahl said a seedling will grow into an effective insect-fighting tree in about three years. His company has a recipe for insecticide for the skin made from neem leaves.
Ted Radovich, a specialist at the University of Hawaii-Manoa’s Sustainable and Organic Systems Farming Laboratory, said neem oil, an extract from the neem plant that is available commercially, is "an extremely common active ingredient in pesticides and fungicides." But he warned that studies show the oil might adversely affect fish. "You have to watch where it’s draining," he said.
HOME REMEDIES for keeping mosquitoes from alighting on skin and biting are common. Barbara Fahs, an herbalist who started Hi‘iaka’s Healing Herb Garden on the Big Island, provides her visitors with a lotion she makes from essential oils of herbs she grows, including citronella, lemongrass and basil.
"It’s a tried-and-true remedy that people have used over the ages," said Fahs, whose recipe is available at gardenguides.com/68174-make-homemade-mosquito-repellent.html.
Fahs also battled mosquitoes in her garden by removing plants like heliconia and bromeliads that allow water to pool. "I had to tear out all my bromeliads a few years ago … because you could see the squiggly little larvae swimming around right in them."
Anti-mosquito measures have had varying degrees of success in Hawaii. Jon Winchester, a graduate entomology student at UH-Manoa who has been studying the history of mosquito control in Hawaii, said one of the two species of mosquitoes capable of transmitting dengue fever was eradicated on Oahu during the war years by spraying the now-banned DDT in urban areas. That species, sometimes called the yellow fever mosquito, is now present only on the Big Island, he said.
The other — the Asian tiger mosquito — has been difficult to eradicate because it lives in forested areas, Winchester said.
"If a black-and-white mosquito bites you, especially on Oahu, that’s the one," he said. "Also, it doesn’t make the whining noise. So if you hear the noise, it’s a different kind of mosquito."
» Barbara Fahs is a herbalist who started Hi‘iaka’s Healing Herb Garden on Hawaii island. The above article had an incorrect first name.