Marigolds Proven to Deter Whiteflies From Tomato Plants

12th March 2019

Companion planting has long been a popular organic gardening method. This is when plants are planted alongside each other for beneficial reasons. One of the most well known planting companions is french marigolds planted next to tomato plants, to deter whiteflies. A new study by scientists at Newcastle University have proved that this method works and is not just an old gardening myth.

The research team, was led by Dr Colin Tosh and Niall Conboy. The researchers carried out two big glasshouse trials. Working with french marigolds in the first experiment, they established that the repellent effect works and that marigolds are an effective companion plant to keep whiteflies away from the tomato plants.

Newcastle University PhD student Niall said: “We spoke to many gardeners who knew marigolds were effective in protecting tomatoes against whiteflies, but it has never been tested scientifically. We found that the chemical which was released in the highest abundance from marigolds was limonene. 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. Most pesticides are sprayed onto the crops. This doesn't only kill the pest that is targeted, it kills absolutely everything, including the natural enemies of the pest.”

Buy french marigolds for your greenhouse at Thompson and Morgan HERE

Read more about the benefits of the popular organic gardening method of companion planting HERE

Read the full Newcastle of University research paper HERE