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Gardening with Laurie: Knowing insects' life cycles helps eliminate the pests

June 19, 2014 at 1:19 a.m.


The past couple of weeks have certainly brought a lot of questions about worm problems in trees, especially pecan trees. This particular pest is called a walnut caterpillar. It loves to feed on the foliage of several types of trees - walnut and pecans being two favorites.

Walnut caterpillars come from walnut caterpillar moths. The moths are about 11/4 inches long with light brown-colored wings that have four darker-colored lines on them. Female moths lay their eggs in groups on the underside of the tree's foliage. The eggs hatch within a few days into the caterpillars that we then discover on our trees.

As soon as the caterpillar larvae hatch, they start feeding on the foliage. And after they have eaten on the foliage for a while, they will stop feeding, all congregate together on a lower limb or the tree's trunk and molt. Then, they go back up into the tree to continue eating. They will molt several times before moving on.

Each time they molt, you will notice they leave behind a patch of fur-like hair and cast skins.

When caterpillars have gone through all of the molting stages and are finished feeding, they drop to the ground and pupate in the soil. They do not spin a cocoon but form a naked pupal case.

Here the caterpillars turn into moths that will then emerge from their pupal case to lay more eggs, and the cycle repeats over and over until they are eliminated.

So just how do we organically get rid of this unwanted caterpillar? Well, first of all, if you've ever had problems with walnut caterpillars before, chances are they will return.

Remember how they drop to the ground when they are finished feeding and then go into the soil to turn into a moth? That means momma moth will emerge from the ground somewhere under or near the tree where you first discovered the caterpillars.

It would be advisable to lightly disc up all the area to eliminate the pupating caterpillars, but I doubt many people want to do that to their lawns.

Putting out beneficial nematodes while the caterpillars are in the soil will help eliminate many of them.

When first noticed in the trees, spray all the foliage with Spinosad or a BT (Bacillus thuringiensis) product.

If you can catch the caterpillars as a group when they have all come together to molt, you can easily spray them with some Neem Oil.

Knowing the life cycles of insects can help all of us natural gardeners deal with them more effectively.

Until next time, let's try to garden with nature, not against it, and maybe all our weeds will become wildflowers.

Laurie Garretson is a Victoria gardener and nursery owner. Send your gardening questions to laurie@vicad.com or in care of the Advocate, P.O. Box 1518, Victoria, Texas 77902.

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