Gardening Harmful insects Vegetables

Do Red and Purple Vegetables Repel Insects?

“Oops! Something tells me that my camouflage isn’t as effective as it used to be!” Source: cuttspoetrycorner.blogspot.com, http://www.iconspng.com & Shelly, lh5.ggpht.com, montage: laidbackgardener.com

Some gardeners claim that red- or purple-leaved vegetables are more resistant to insect attack than green ones. Red cabbages, purple kales, purple beets, etc. are, in their experience, less often affected by some insects, including caterpillars and aphids.

Perhaps this is because the odd coloration of the foliage makes the insect’s natural camouflage less effective?

Does the mother insect, usually pale in color, feel more exposed when she lands on a purple leaf and so moves to a greener plant where she feels more at ease? Or maybe she lands just as easily on a dark-leaved plant despite its color, but its predators notice it faster on purple foliage and eat it, ending the infestation before it even starts? Or see its white eggs or pale green larvae more easily and consume them before they do any harm?

20181213B www.planetnatural.com
I bet you spotted this cabbage looper right away! The contrast between the pale green insect and the purple leaf is striking. Source: http://www.planetnatural.com

One thing is certain: humans can more easily spot pale-colored insects and eggs on purple or red foliage and so can react faster by manually harvesting the intruder or treating with a pesticide. For example, a cabbage looper caterpillar, with its pale green color, is perfectly camouflaged on a green leaf and therefore almost invisible, but stands out like a beacon when it’s on a purple leaf.

It would be interesting for someone to do a study to see if it’s true that purple and red vegetables are initially less attractive to insects. It sounds to me like it might be a simple yet interesting summer project for students interested in horticulture!

Larry Hodgson is one of Canada’s best-known garden communicators. After studies at the University of Toronto and Laval University where he obtained his B.A. in modern languages in 1978, he succeeded in combining his language skills with his passion for gardening in a novel career as a garden writer and lecturer. He has notably been editor-in-chief of HousePlant Magazine, Fleurs, Plantes et Jardins, À Fleur de Pot and Houseplant Forum magazines and is currently the garden correspondent for Le Soleil and radio garden commentator for CKIA-FM Radio. He is a regular contributor to and horticultural consultant for Fleurs, Plantes, Jardins garden magazine and has written for many other garden publications in both the United States and Canada, including Canadian Gardening, Harrowsmith, Horticulture, Fine Gardening, Rebecca’s Garden and Organic Gardening. He also speaks frequently to horticultural groups throughout Canada and the U.S. His book credits include The Garden Lover’s Guide to Canada, Complete Guide to Houseplants, Making the Most of Shade, Perennials for Every Purpose, Annuals for Every Purpose, and Houseplants for Dummies, as well as nearly 50 other titles in English and French. He can be seen in Quebec on French-language television and was notably a regular collaborator for 7 years on the TV shows Fleurs et Jardins and Salut Bonjour Weekend. He is the President of the Garden Writers Association Foundation and the winner of the prestigious 2006 Garden Media Promoter Award offered by the Perennial Plant Association. An avid proponent of garden tourism, he has lead garden tours throughout Canada and to the gardens of over 30 countries over the last 30 years. He presently resides in Quebec City, Quebec.

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