What can I do about the ugly mass of web on the limb of my pecan tree? Can I burn it off?
These are questions that I get every year about this time because of an insect called the fall webworm. The fall webworm has one of the widest host ranges of any caterpillar. In our area, you will find them on pecan, walnut, elm and many other trees, but pecan is infested the most. Fall webworms usually will eat some of the leaves off the limbs in the area of the web, but they don't defoliate the tree.
Fall webworms can have up to four generations in a year, with most of the activity occurring in late summer and early fall. The larvae or caterpillars are hairy with distinct paired dark spots on each segment of the back. They can be variable in color, but the primary color in our area will be whitish-yellow to pale green with white hairs.
The caterpillar will be about one inch long when mature, and will twitch and jump about when disturbed to deter potential predators. The caterpillars will turn into a moth that is satiny white with a wingspan of one-and-a-half inches.
THE FALL webworm will winter as a pupa in a flimsy light-colored cocoon. These cocoons can be found in protected areas such as bark furrows, crevices along the sides of buildings and under mulch and debris.
The adult moths will emerge in June to July and begin laying eggs on the underside of leaves. When the eggs hatch, the young larvae feed together. They will skeletonize the leaf and then start to form their web. The web is made of silk, and into this is incorporated leaves and branches to support the web.
The young larvae do all of their feeding inside of the tent. When they run out of food, they make the tent larger. If you look into the tent of the fall webworm, you will find leaf fragments, droppings and cast skins. When full grown, the caterpillars leave the tent to find a protected area for the winter.
SO HOW DO we go about controlling fall webworms? The best way to control them is to remove the web from the tree as they form. You can use a pole pruner to reach them and remove the portion of the limb that has the web on it. Since fall webworms don't feed outside of the web, this will remove all of the caterpillars.
There are insecticides that you can use, but they can be hard to apply since most of the webs are high in trees.
What about burning the webs out? Burning will cause more damage to the tree than the caterpillars do.
Another insect that shows up this time of year is the red-headed azalea caterpillar. This is a serious defoliator of azaleas. The azaleas look great one day and the next, they have no foliage. These insects prefer indica azaleas.
These caterpillars are brightly colored, with yellow and black bodies with red legs and head. When you touch these caterpillars, they arch backwards forming a C.
The female moth lays 80-100 eggs in a cluster, so there will be a large number of caterpillars on one shrub. This caterpillar seems to over-winter in the pupae stage. The adult emerges in early summer and lays her eggs, which hatch in late August or early September.
These caterpillars can be controlled with different insecticides, including Sevin, carbaryl. The liquid form works the best. Follow the directions on the label to spray Sevin on the plant. The other control is to use Dipel or another product that contains Bacillus thuringiensis. We commonly call this Bt. This is an organic control that works well on caterpillars. This is applied to the plant and when the caterpillar eats the foliage, the caterpillar is infected with a fungal disease and dies.
ANOTHER CONTROL option is to remove the limb with the caterpillars. If you find the caterpillars while they are small, they tend to be congregated on one or two limbs. You can remove these limbs and get rid of the problem.
The best thing that you can do for now is to scout your plants for these pests. When you find the small caterpillars, you then can treat. The smaller the caterpillar, the easier it is to control. If you find some caterpillars and need help identifying them, I will be glad to identify them for you.
Columbia County Extension Agent Charles Phillips can be reached at (706) 868-3413 or by e-mail at firstname.lastname@example.org. The Extension Web address is www.ugaextension.com/columbia.
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