caterpillar

Walnut caterpillars set up house on a tree at a local residence in Calcasieu Parish. The voracious pests have been eating up foliage on trees all over the state.

For many people in Southwest Louisiana, summer is meant for spending more time in their yards cutting grass, planting, and pruning. But many residents in the area have found that some voracious little critters have been quietly going about their business and have done some pretty severe pruning of their own.

Meet the walnut caterpillar.

If you haven’t encountered the hungry pests, count yourself lucky. A query from the Southwest Daily News on a local Facebook page brought a multitude of responses from people experiencing the joy of playing unwilling hosts to the walnut caterpillars.

Teri Newhouse-Berry said, “Its like a calvary of caterpillars overtaking my porch, my yard, everywhere.”

“These things are a nightmare,” posted Adysen Ray.

And Sam Hall added, “They are all over our pecan trees — house and grounds. This is an annual event.”

According to information obtained at Horticulture News (https://hortnews.extension) walnut caterpillar moths emerge from the ground in late spring or early summer after spending the winter underground in the pupal stage. They lay eggs in masses of 300 or more on the underside of host plant leaves found on pecan, hickory, and walnut trees.

Small, newly-hatched larvae are light yellow-green in color and about a quarter inch long. They eat only the leaf material from between the veins. Middle-sized larvae (one half to 1.5 inches long) are dark red with four longitudinal white stripes on each side of the body. They consume the entire leaf except the petiole. The full-grown caterpillar is about two inches long, has a dark, black body with long, whitish-gray hairs. The black, fuzzy, full-grown caterpillars drop or crawl to the ground and search for a protective site to pupate.

Walnut caterpillars move and feed in clusters until the last larval stage. The clusters are frequently noticed when they move to the trunk or a large limb to molt, leaving behind an unsightly “hairball” of shed skins on the trunk as the cluster returns to the foliage and continues feeding. When disturbed, the larvae arch their head and tail into the air as though fighting off a predator.

To control an infestation of walnut caterpillars it is suggested that homeowners use Bt (Bacillus thuringiensis) found in products such as Dipel, Thuricide, and Caterpillar Killer and products with spinosad such as Green Light Lawn and Garden with Spinosad, or the use of wetable Sevin (Carbaryl) plus soap. Another remedy, if you are lucky enough to spot them on the trunk of the tree, is to spray the cluster with dish soap and water, about 10 drops to 24 ounces of water.

Though the caterpillars are unlikely to harm a mature tree they will produce some unsightly results causing severe defoliation in some cases.

As one person described the noises of them feasting, “It sounds like rain falling on the tree leaves when I stand under it.”

Whatever stage of the lifecycle you find your walnut caterpillars in, never fear. There are usually two and sometimes three generations during the spring and summer months. So if you miss them this go around, just wait — they may be coming back.