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Love it or hate it

发布时间:2019-03-07 06:06:01来源:未知点击:

By Jeff Hecht THE active ingredients in catnip that drive cats crazy also repel cockroaches, researchers in Iowa have found. The discovery paves the way for the development of natural repellents that could be added to food packaging to deter marauding insects. Insects steer clear of certain plants, but traditional pest repellents fell out of favour because they seemed less effective than heavily marketed pesticides, which kill insects instead of merely sending them on their way. However, the most potent insecticides can pose risks to humans, pets and the environment. Joel Coats of Iowa State University in Ames has been studying potential applications of compounds that plants have evolved to deter insect attack. Earlier studies showed that roaches avoid catnip, a member of the mint family, but no one had identified the compounds responsible for the effect. Coats and his colleagues pinned their aversion down to a compound known as nepetalactone and showed that it keeps cockroaches out of areas treated with it. Catnip contains two forms of nepetalactone, with the same atoms arranged in different configurations. Both repel roaches, but the less-common form has a stronger effect, Coats and his colleague Chris Peterson told a meeting of the American Chemical Society in New Orleans last week. The isolated compounds smell a little different from catnip. “One is lemony and the other peppermint,” says Peterson. “It’s a very pleasant odour.” They belong to a class of essential oils that give the members of the mint family their distinctive scents and tastes. Nepetalactone intoxicates cats as well as repelling roaches, but has no obvious effect on humans. One attraction of natural repellents is that their lower toxicity would allow them to be added to food packaging, reducing food losses and perhaps keeping the pests out of food shipments. If tests show the compound is also effective against mosquitoes, it could also prove an effective personal insect repellent. “The effort is to make mosquitoes leave the body alone rather than to eradicate them,” says Peterson. The team has also been working on the “osage orange” or “hedgeapple” fruit of the tree Maclura pomifera, a thorny member of the mulberry family that early settlers in the central US planted as hedgerows to keep in livestock. Coats, who grew up on a farm in the region, knew the fruit was supposed to repel roaches, spiders, other insect pests and even mice. “Nothing could eat it as far as we can tell,