A couple of weeks ago I received an email from a Costa Mesa gardener.
It began “for the past few years I have been battling walking stick insects. They are voracious. The problem 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 re
quire a mate to reproduce. One female can lay more than 1,500 eggs during its 18 month lifespan. So a single La Jolla walkingstick 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.
The original walking stick location in La Jolla is so overrun that local gardeners describe the problem with such terms as “inundated”, “a nightmare”, “infested” and “decimated”. Locals report thousands of the insects chewing their way through the gardens. A gardener in the neighborhood showed a hawthorn branch that he'd cut off the tree, with 50 walking sticks "frozen" on the branch trying to look like twigs.
Like other exotic pests that quickly get out of control, Indian walking sticks have no natural predators here. Crows will pick at them, but since the “sticks” are nocturnal they’re not much help.
At the moment it does not appear that any of the Orange County infestations are as serious as those in San Diego County, but that could change.
Among solutions, the current favorite, although a bit brutal, is the late night Edward Scissorhands approach. Say’s one gardener, “I'm out there with a big flashlight and a pair of scissors, snipping the suckers in half.”
But finding them is no easy task. One gardener says to look for their antennae sticking out from under the leaves. Shine the flashlight on the leaves of the affected plants and look for a couple of little hairs (their antennae) protruding. With some practice, you can spot them pretty quickly. She adds, “All of this night-time hunting is greatly enhanced by bringing a nice glass of Cabernet out with you (I use a plastic glass since I can get pretty excited when I spot one) and taking time to look at the stars while you're at it!”
Another gardener shares here favorite control method: “My favorite way of getting rid of them, is filling a bucket with water, putting on my gardening gloves and spraying the heck out of my plants with a hose. They hate water and will all come scurrying to the tops of the plants. I just pluck them off and dump them in the bucket of water. They don't really try to get out, they just sit there and drown quite quickly. I’ve filled buckets.”
Martha, I wish I had a better answer for you. If you supply the wine, I’ll bring the scissors.
Questions from Readers January 31.
Ron Vanderhoff is the Nursery Manager at Roger’s Gardens, Corona del Mar.