The Coastal Gardener:

New pest walking through the garden

January 30, 2009|By RON VANDERHOFF

A couple of weeks ago I received an e-mail from a Costa Mesa gardener. It began “for the past few years I have been battling walking-stick insects. They are voracious. The problem is both summer and winter. I live in Newport Heights, down the street from Newport Harbor High School. Any help on how to rid my garden of them?”

It’s not a case of mistaken identification. Yes, walking-stick insects have invaded many southern California neighborhoods and many gardeners are near the end of their rope. Like Martha in Newport Beach, they don’t know what to do.

Although harmless to gardeners, walking-stick insects are voracious plant feeders and reproduce abundantly. Scientifically known as Carausius morosus or Indian walking stick, this insect mimics the slim branches and twigs of many of the plants it feeds upon, hence its name.


It is especially active at night and often goes undetected for months, while all the unsuspecting gardener sees is decimated leaves and tattered foliage. Indian walking sticks vary in color from pale green to light brown and can grow up to 6 inches long, feeding on almost any plant it happens along, including ivy, vines, roses, annual flowers, tomatoes, orchids, an array of shrubs and even succulents.

Walking sticks are well adapted to life in Southern California, although they are native to southeastern India. They are now reported as garden pests from San Diego County to as far north as San Luis Obispo County. Most likely, this exotic insect was introduced to our gardens via the Internet.

There’s no way of knowing whether all of the walking sticks in Southern California are descendants from the same single ancestor, but it is possible.

The speculation is that one Indian walking stick, purchased in 2001 on the Internet by a teenager in La Jolla, might be the forbearer of all the rest.

Walking sticks are parthenogenic, meaning they don’t require a mate to reproduce. One female can lay more than 1,500 eggs during its 18 month life span. So a single La Jolla walking stick may have done just that — walked. And its progeny kept walking, and walking and walking — all the way to Newport Beach and beyond; and to Martha’s garden near Newport Harbor High School.

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