Southern IPM Center Enhancement Grant Leads to New Product for Use in Controlling Horn Fly on Organic Cattle

The horn fly is the most important pests of pastured cattle in the United States. Flies feed on cattle, reducing milk production and weight by as much as 15%. Typically, dairy farmers manage horn flies by using broad-spectrum insecticides and must be applied two or three times per month.

For organic dairy farmers, however, there are few options available to manage the pest. Geraniol, a natural, minimal risk insect repellent, was listed as one of the products that could possibly repel flies. In 2007, North Carolina State University researcher Wes Watson used a Southern Region IPM Center IPM Enhancement Grant to test whether geraniol would repel the insects, and whether the substance would change the taste of the milk. Repeated experiments showed that horn flies were repelled from cattle treated with geraniol and did not return for at least 24 hours. The researcher recommended treating a small portion of the herd with a conventional insecticide (to kill insects repelled by the geraniol) and the majority of the herd with the geraniol. In addition, taste tests showed that geraniol was not detectable in milk, making it a substance that would not hamper dairy sales. For the 16-week season for horn flies, geraniol saves growers between $4 and $8 on other insecticides and gives them an alternative to permethrin, at a similar cost. As a result of the study, the Organic Materials Review Institute registered the first geraniol product for use on organic cattle as a fly repellent, and some organic pest control distributors are selling it online.

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