San José, Costa Rica, since 1956

Bite Free, Naturally: Plant-based Mosquito Repellents

THERE’S nothing worse than an itchy mosquito bite – or is there? Some fear that dousing themselves with harsh chemical repellents such as DEET may do more harm than the bite itself. Fortunately, natural alternatives are available that can work just as well as chemical repellents to keep mosquitoes at bay.Though flowers and fruits probably aren’t the first things that come to mind to ward off insects, several have natural repellent properties, including chrysanthemum, citronella and guanábana, a tropical fruit common in Costa Rica. The leaves and seeds of these plants can be used in repellents to keep mosquitoes off the body and out of the home – particularly important during this year’s rainy season, which has seen increased cases of mosquito-transmitted dengue fever (TT, Aug. 12, 19).Though the U.S. Centers for Disease Control (CDC) Web site recommends using repellents containing DEET to prevent mosquito bites, scientists warn that this chemical has a negative effect on the environment.Because DEET remains active and never fully decomposes, it can be harmful to plants and beneficial insects, said Jorge Arce, professor of tropical cultivation and medicinal plants at Earth University, in the Caribbean-slope town of Guápiles.Natural Repellents for the Skin Several fruits commonly found in Costa Rica have repellent properties, Arce explained. For example, anona, a sour apple-type fruit, is one of the strongest natural repellents. In the same family, guanábana and cherimoya fruits, which can be found in local supermarkets, are also effective at repelling mosquitoes.Neem, a plant long used medicinally in India and Mexico’s Yucatán Peninsula, is another natural mosquito-fighter found in Costa Rica. Lemongrass, citronella and garlic also have strong repelling properties.To take advantage of any of these natural repellents, Arce recommends making your own spray by drying the seeds, in the case of fruit, or the leaves, in the case of plants, and then grinding the dried substance into a fine powder. Dissolve about 10 milliliters of the powder in one liter of water to form a solution (the solution should only contain about 1% powder).The result: your own, natural version of OFF! that can be sprayed all over the skin.A note of caution: While natural repellents are quite effective, they wear off more quickly than chemical versions, and should therefore be reapplied more frequently, at least once an hour.If making your own repellent sounds like too much work, you can always buy a pre-made natural spray, such as Green Screen, which contains citronella, eucalyptus and spearmint – all plants distasteful to mosquitoes. A 120-milliliter bottle costs ¢3,000 ($6.20) at Centro BioSalud, which has Central Valley locations in Escazú, Heredia and Curridabat.Natural FumigationIf mosquitoes have invaded a home, the power of plants can be used to drive them away. The chrysanthemum flower is effective in killing not just mosquitoes but also gnats, spiders, cockroaches and other uninvited critters.Natural fumigation specialists Control Ecológico de Plagas Crisantemo S.A., based in the northern San José district of Tibás, uses a chrysanthemum-based spray for home fumigation. Being a mosquito magnet, I decided to try it out in my apartment, which suffers from a plague of gnats and occasional mosquitoes, whose presence seems to increase with each raindrop.Fumigator Jhon Jairo Acevedo came to my apartment armed with what appeared to be traditional fumigator gear – goggles, a jumpsuit and a small tank, connected to a hose with a sprayer on the end. However, instead of smelly toxins, the tank contained a mix of natural ingredients and a harmless chemical that attracts and later kills mosquitoes and other bugs. The mix is biodegradable, toxic only to insects, and has been approved by the Health and Agriculture Ministries, as well as the U.S. Environmental Protection Agency (EPA).Piperonyl butoxide, a powdery substance, is mixed with ground chrysanthemum and water to form a toxic cocktail for insects. Sprayed around the perimeter of a room and over the entire ceiling, the piperonyl butoxide attracts bugs away from their homes, Acevedo explained. Shortly after, the poisonous chrysanthemum kicks in, and the insects crawl or fly to their deaths.I had the amusing experience of witnessing the substance’s effect on two cockroaches that appeared out of cracks in the floor right after Acevedo sprayed. With their normal scurrying capacity disabled, they appeared drunk and stumbled to their demise within minutes.Dead gnats and mosquitoes on the floor provided additional evidence of the natural spray’s power – these flying insects tend to hide on ceilings, but quickly die upon contact with the spray, Acevedo said. An invisible powder residue left by the spray remains in the home and continues to attract and kill mosquitoes and other bugs as they surface.One treatment lasts about three months and costs ¢16,000-80,000 ($33-165), depending on the size of the home and the severity of the problem.For more information, call Control Ecológico de Plagas Crisantemo at 236-4414 or 236-2994.Natural Repellents forthe HomePlacing repellent-containing plants around your home will also repel mosquitoes, Arce said. The incense plant (Calomeria amaranthoides), when kept inside the house and planted nearby outside, can send mosquitoes flying in the opposite direction with one whiff. Additionally, cilantro, particularly the wide-leaf variety, can serve as both an herb for cooking and a mosquito repellent when kept in the kitchen.

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