Agricultural insect pests seek out familiar scents to find their plant hosts. However, they can also be repelled by odors from other plant species. A new study from the University of Vermont published in Scientific Reports offers a novel framework for exploiting plant odors to repel insect pests. The study is the first to show how the similarity of plant odors and phylogenetic relatedness can predict insect repellency.

The team applied this conceptual framework to swede midge, a tiny fly that is becoming a major problem for Northeastern growers of broccoli, kale and other cabbage-family crops. They found that particular essential oils -- garlic, spearmint, thyme, eucalyptus lemon and cinnamon bark -- were most effective at repelling the midge. The findings come as good news to organic farmers who are without an effective solution for managing the pest. While essential oils have long been used in pest management, determining which oils are effective has followed a "trial by error" approach, said senior author Yolanda Chen, associate professor in UVM's Department of Plant and Soil Science.

"People often think more aromatic plant oils, like mint, basil and lavender will repel insects, but usually there is no rhyme or reason for choosing," said Chen, who is also a fellow of UVM's Gund Institute for the Environment. "It turns out that as we go along the family tree, plants that are more distantly related from the host plant are generally more repellent."

(Source: Agriculture and Food News, ScienceDaily.