Publishing their findings today in the journal PLOS ONE, the experts have identified limonene—released by marigolds—as the main component responsible for keeping tomato whiteflies at bay. The insects find the smell of limonene repellent and are slowed down by the powerful chemical.
The findings of the study have the potential to pave the way to developing a safer and cheaper alternatives to pesticides.
Since limonene repels the whitefly without killing them, using the chemical shouldn't lead to resistance, and the study has shown that it doesn't affect the quality of the produce. All it takes to deter the whiteflies is interspersing marigolds in tomato plots, or hang little pots of limonene in among the tomato plants so that the smell can disperse out into the tomato foliage.
Read more at: https://phys.org/news/2019-03-humble-marigold-outsmarts-devastating-tomato.html#jCp