Posted by: T. Boyd | March 14, 2011

Nature’s pruners

There are four things on earth that are small but unusually wise ( Proverbs 3:24 – New Living Translation)

The writer of Proverbs goes on and talks about the ant, the rock badgers, the locusts, and the lizards, but he could have included the beetle as well.  Our Father, the designer and maker of all the wondrous creatures on the earth, shows His care for tiny details in the amazing insects spoken of here.

Have you wondered about all the twigs and small branches that fall to the ground under a hardwood tree this time of year? The ones I am talking about are those that look like they have been cut and not just broken off. An older friend explained this annual event to me several years ago, and I was reminded about it this year – our new home has a large deciduous tree in the backyard with dozens of these cleanly pruned stems lying on the ground under the tree. Here is a photo of some of the twigs that I gathered:

twigs pruned by twig girdlers

I think the scientists call this symbiosis – where one biological species helps another. And, as always, I think it was God’s intent for these arrangements to be made, not, as many think, an accident of the survival of the fittest.

He made at least two insects that prune these trees each year: twig girdlers, and twig pruners. They are both small beetles, but do the pruning in significantly different manners. The girdler adult beetle selects a small limb to crawl out on, goes near the end – typically 1 foot from the end – and girdles the twig by cutting the bark all the way around. Then she lays one or more eggs in incisions made on the rim of the cut on the side away from the trunk of the tree. This is usually in the early fall season. About a month later, the egg will hatch, and the larva will start eating inside the bark.

The larva would die in a healthy limb, but does well in the damaged tip. Eventually the end of the limb will break because of the wind or other weather affects (sometimes the limb will stay attached, but hang down by a “thread” of wood fiber). The larvae  continue eating several months inside the dead twigs and emerge as an adult beetles in the late summer. Then the cycle begins again.

The photo on the left shows an adult twig girdler at work (from U of Florida, Gardening Solutions).   The one on the right is a photo of an adult twig pruner
from Rainbow Treecare

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Twig Gridler

twig pruner adult

In contrast to the girdler beetle, for the pruning beetle, it is the larva that does the cutting. The adult female cuts a hole in a twig near the end, doing this in the spring. When the larva hatches, it begins eating the wood, and finally tunnels around near the peripheral, making a circular cut around the twig, but from the inside, leaving the outside layer of bark uncut. But, again, the wind will cause the weakened tip to break off later in the year. The only difference in the broken twig’s appearance between the pruner is that the outer bark will have a ragged edge where it broke off compared to the girdler – which leaves a clean cut. The diagram below shows the difference – you can click here for more information, and thanks to University of Missouri for supplying the diagrams and for how to control the infestation when it gets out of hand.

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Adult female twig girdler chews a V-shaped groove from the outside inward, leaving a ragged center where the twig breaks and a smooth cut on the outside near the bark.

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Full-grown twig pruner larvae chew through the wood from the inside outward, leaving a smooth cut on the inside of the twig with ragged edges near the bark where the twig breaks.

Again, the mysteries of creation, speak of the wonderful creativity, and may I say, it also tells of the sense of humor for the variety of funny looking creatures by our wonderful Father in heaven, and His Son, Jesus, through Whom the creation was made. “For by Him all things were created, both in the heavens and on earth” (Colossians 1:16)

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