Control Pests With Praying Mantis

Maureen Gilmer explains the advantages of the praying mantis in the garden.

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Adult mantids with their triangular heads that can turn 180 degrees may appear frightening, but they are the gardener's best friend. (SHNS photo by Maureen Gilmer)

I've had a praying mantis epiphany. Did you ever notice how a praying mantis' head resembles an alien's head?

I guess we all share the same conclusion as Fox Mulder on the X-Files — a praying mantis does look like an extraterrestrial. Maybe it's how they turn their heads 180 degrees. Or maybe it's their very large size. Despite their odd, sometimes frightening appearance, this insect is the gardener's very best friend.

In the world of biological pest control weapons, praying mantises are howitzer cannons. They are efficient carnivorous predators that consume some of the more problematic species. Mantids put a big dent in leaf-eating pests. They go for beetles and grasshoppers in both vegetable and ornamental gardens.

They are among the few nocturnal hunters capable of catching and eating moths. While moths themselves aren't a problem for gardeners, the moth's highly destructive larvae can devastate whole plants in a matter of days. Best of all, mantids love to eat roaches.

Praying mantises don't have a larval phase. Their young are born fully formed as nymphs. Considerably smaller than a grain of rice, they leave the egg case to molt at least a dozen times before achieving adult size.

Moments after emerging, hungry mantid nymphs are ready to begin hunting for living prey. (SHNS photo by Maureen Gilmer)
When conditions are right, tiny mantid nymphs explode out of their egg case fully formed. (SHNS photo by Maureen Gilmer)
Keep a sharp eye out for mantid egg cases to salvage when pruning or cleaning up the garden. (SHNS photo by Maureen Gilmer)

Female praying mantises mate in late summer. It is true that they sometimes bite the head off the one they love. But a female does not always eat her lover. Males do get away fully alive after consummating the union.

In autumn the female will lay her eggs before she dies with the frost. She often deposits them on a branch or twig, but also leaves them on walls, fences and eaves. They are surrounded by a frothy liquid, called ootheca, which hardens into an egg case about the size and shape of a cigarette filter.

The following spring the nymphs hatch and burst out of the case in a small army of hungry youngsters, each the size of a small ant. From birth mantids are predators. The nymphs immediately begin attacking leafhoppers, aphids and even small flies.

It's important for every gardener to recognize these egg cases that become most visible in the winter when deciduous trees and shrubs lose their leaves. When pruning, keep a sharp eye out for them. Any found on twigs and branches should be set aside in protected parts of the garden. If they must be removed from a wall, for example, simply relocate to a sheltered place, and the nymphs will survive. Never put an egg case on the ground; the eggs inside quickly will be consumed by ants.

A healthy organic garden relies on a delicate balance of predator and prey species. Beneficial mantids, lacewings and ladybugs are vital to keeping plant damaging insects under control. Just one blanket application of chemical pesticides can wipe out whole populations of mantids that can take years to reestablish. In the meantime, plant-damaging pest insects will return in droves to infest the garden, proliferating without any threat of predators.

If your mantid population has been wiped out or if you want to expand the current population, buy dormant mantid egg cases. They are available in most garden centers or online garden-supply stores. They are sold in sets of three for less than $10, ready to distribute around your garden. Each case contains about 200 eggs, and three cases will cover about 6,500 square feet.

Position your egg cases in the crotches of trees and shrubs. Use wire or twine to tie them to branches. Set on shelves or ledges in wood fencing or structures. They prefer a warm location and will hatch after the last frost and 10 to 15 days of warm weather.

While gardens may appear to be peaceful loving environments, they are, when healthy, ruled by ferocious insect predators vital to population control.

So if you have an aphid problem this year, or if Japanese beetles are eating your cabbage, don't say a prayer; release mantids instead. They are God's own chemical-free pest control pets.

Maureen Gilmer is a horticulturist and host of Weekend Gardening on DIY-Do It Yourself Network. For more information, visit: www.moplants.com or www.DIYNetwork.com.

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