Horticulture Hotline 09/06/21
Bill Lamson-Scribner
The Fall brings many webs to our Lowcountry trees. The webs are for protection against birds and other insects. Some are bad for the tree; some are good for the tree and some are just Halloween decorations!
The web that is very close to the trunk and main branches, like a white stocking pulled tightly against the bark, are tree cattle. Tree cattle or bark lice are beneficial insects that clean organic matter out of the crevices of the bark of the tree. They do no harm. If you are a “web-a-phobic” you can spray the webbing off with a high pressure hose; however, you will be ridding your tree of a free maid service.
The web that is out at the tips of the branches engulfing the foliage, are Fall Webworms. The worms should be visible as well as half eaten foliage. Webworms tend to favor pecan, river birch, walnut, hickory, persimmon, sweet gum, fruit trees and some maples. In the forest, natural predators do a good job of keeping this pest in check. In your landscape consider the size and age of the tree before treating. We usually only recommend treating in very severe cases because many of the trees that get attacked are going to lose their leaves soon enough anyway in the fall.
Even though they are called Fall Webworms, they can appear here as early as June or July. They over winter in the pupal stage in bark crevices and in leaf litter. Some people will try to control this stage with Lime/Sulfur mix and horticultural oil before budbreak. Not too easy for many homeowners with a large pecan tree. Homeowners can treat around the base of the tree and up the tree with Caterpillar Killer, Bifenthrin, Acephate, Sevin or Lambda- Cyhalothrin. Homeowners can also call in a professional.
When the leaves appear on the tree, the adult moth emerges from the pupal stage and lays eggs on the underside of the new leaves. The eggs hatch and here comes the hungry caterpillar – eating the leaves and spinning a web for protection against birds and predatory insects. Since a moth that flies lay the eggs, a product like Tangle Trap or Tree Tanglefoot are not necessary for this caterpillar.
If your tree is young and you can easily spray it, use Bt (a bacteria that affects certain insects – biological warfare!). Organic products containing Bt are; Caterpillar Killer and Dipel. The webworms devour the foliage on trees. The foliage is what the tree uses to collect sunlight and to make food for itself. The repeated defoliation of a tree can permanently injure the tree. Spray the leaves next to the nest and the nest itself with Bt, and when the webworms eat the leaves, the bacteria will make them sick. It is best to catch the worms while they are young when using Bt. If you do not want to spray, you can open up the webs with a stick, stream of water or pole saw and let the birds and other predatory insects have a feast.
Now is a good time for planning and planting. While planning your new landscape additions this fall, don’t forget the amendments to your soil. Amendments will help to ensure a healthier plant next summer when the heat is on by growing a stronger root system throughout the Fall and Winter. Soil test now for your 2022 program and any new areas that you are adding this Fall. Any of the Back To Nature products (Cotton Burr Compost, Natures Blend, Composted Cow or Chicken Manure) will greatly improve your soil and your plants health.
