Laidback Gardener Tip of the Day

Bugs that Spread Plant Diseases

Spittlebug larvae live in a mass of bubbles commonly known as frog spit or snake spit.

Insects that feed on the sap or grate or eat the leaves of our plants sometimes have much more serious consequences: they may well be carrying an incurable plant disease that will cause more damage that the insect itself ever did. Plant viruses and their relatives, viroids and phytoplasmas, are mostly transmitted by insects that inject them into plant tissues as they eat. However, there is no treatment for viruses in the home garden except to pull out and destroy the plant. This is why it is important to act quickly when a plant is attacked by any insect. Among the insects that transmit viruses are aphids, flea beetles, leafhoppers, whiteflies, thrips and spittlebugs (froghoppers).

Grass infected with a mosaic virus… but few plant viruses are this visible.

Viruses (and other related diseases) sometimes have visible symptoms: for example, a specific discoloration of the leaf (mosaic or marbling) or deformed foliage or flowers, but most often not… except the plant becomes weak and less productive. The two classic cases are strawberries and raspberries. Both are very productive for 2 or 3 years, then go so far downhill due to multiple viral infections that the only logical solution is to destroy them and start anew with “indexed” plants (plants confirmed to be free of viruses).

A good way of reducing the attacks of virus-carrying insects in the home garden is to maintain a good biodiversity in your plantings. Monocultures, where a single plant species is grown over a large area, attract and retain predatory insects of the crop being grown. When plants are grown in mixed plantings, though, these insects have a harder time finding their favorite host and your plants are therefore less often infested with debilitating diseases.

Larry Hodgson is one of Canada’s best-known garden communicators. 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 has written for many garden publications in both the United States and Canada, including Canadian Gardening, Harrowsmith, Horticulture, Fine Gardening 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 60 other titles in English and French. He is a past president of the Garden Writers Association (now Garden Communicators International) and the winner of the prestigious 2006 Garden Media Promoter Award offered by the Perennial Plant Association. He resides in Quebec City, Quebec, Canada.

1 comment on “Bugs that Spread Plant Diseases

  1. If I can add just a light bit of humor that the real world authenticity of your post inspired–everybody talks and writes with so much romantic revery about the garden–but as you demonstrated in this post–it is a real war out there–so on to the humor–facts of life step into the garden–could be a good satirical movie with lots of laughs, no?

    Thanks for the post and love your laidback gardener photo!

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