• Farmers have, for ages, cultivated ‘companion plants’ — carrot and rosemary, corn and sunflower, marigold and tomato  — together for no apparent reason.
  • By conducting large-scale glasshouse studies and analysing the marigold flower, researchers from Newcastle University have now identified the chemical compound in the flower that helps repel tomato whiteflies.
  • Limonene, the chemical found in the peels of citrus fruits, were found in the studied French marigold flowers.
  • This is exciting because limonene is inexpensive, it’s not harmful and it’s a lot less risky to use than pesticides, particularly when you don’t apply it to the crop and it is only a weak scent in the air.
  • Limonene has been found to have activity against a number of different insects, mites and microorganisms. It is also commonly used as part of mosquito repellents.
  • So there is a clear potential that this could work for other tomato pests.