A method of warding off whiteflies from tomato plants that’s been passed down from generation to generation of gardeners has been proven effective by researchers.
Findings published Friday in the journal PLOS ONE show marigold plants repel whiteflies – tiny, triangular insects that cluster on fruit and vegetable plants to feed, weakening them and leading to stunted growth.
Researchers at Newcastle University believe a powerful chemical called limonene released by marigold plants is what drives whiteflies away and suggested it may be possible to develop a safer alternative to pesticides.
They said while whiteflies are slowed down by limonene, they aren’t killed by it, which should mean they won’t develop resistance.
The researchers gave a nod to gardeners who were ahead of the game.
“We spoke to many gardeners who knew marigolds were effective in protecting tomatoes against whiteflies, but it has never been tested scientifically,” said Niall Conboy, a PhD student on the research team.
They said planting marigolds alongside tomatoes is effective and hanging “little pots of limonene” among the plants also works.
“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,” said Conboy.
The research was carried out in greenhouses and involved using French marigolds to establish they work as a repellant and using a machine to analyze the chemicals released by the plants.
