Drive around the neighborhood or walk around the yard and you may notice large webs covering tree branches. I’ve been getting several calls and questions concerning what these webs are and how to control them. I’ve also been seeing an increase in social media posts regarding these giant webs, with many people concerned about being invaded by a huge population of spiders. Well for all of you who were horrified by the movie “Arachnophobia” you can breathe a sigh of relief – these are not spiderwebs.

The webs you are seeing are made by caterpillars of the fall webworm moth – Hyphantria cunea. Webs tend to be more prevalent in pecan, persimmon, sweetgum, and bald cypress trees, although these can occur in other hardwood trees and large shrubs. I’ve noticed webs in Vitex shrubs, and I’ve had several calls from homeowners concerned about the webs in their redbud trees.

Despite the name, fall webworms can become active in the spring and preset into the fall. It is normally in the fall when the caterpillars are most active. Seeing the presence of so many webs now could be an indication of heavier populations this coming fall. In Louisiana, we typically have between 3 and 5 generations (pupa to adult/moth to egg to larva/caterpillar to pupa) between spring and fall. The pupae will overwinter in bark crevices and under leaf debris.

Caterpillars feed on tree leaves in a communal web. This web helps to protect them from predatory spiders and birds. The web also makes chemical control with insecticides more difficult. As the caterpillars grow, they will expand the web to consume more leaves.

Caterpillar damage to fruit and nut trees can adversely affect fruit and nut production. Commercial pecan producers can easily spray insecticides with high volume air blast sprayers to control webworm populations. However, this is not feasible or practical for homeowners. Fortunately, although the webs and damage are unsightly, it is seldom detrimental to the tree. Healthy, mature trees can even withstand complete defoliation.

Often, doing nothing is the most practical approach to dealing with fall webworms. I see many posts on social media suggesting burning the webs in the trees kill the worms. I do not recommend this approach, as the fire will likely cause more long-term damage to the tree than the actual webworm, not to mention the potential for something to go wrong.

One mechanical approach that is effective is to use a bent clothes hanger or piece of wire attached to a long pole to tear the webs apart. This exposes the caterpillars to predation. Another mechanical approach to controlling webworms is to prune out webs that can be safely reached with loppers or a pole pruner. This is reserved for incidences when only a few limbs are affected.

Attempts to control webworms with insecticides are more practical on trees that are still small enough to be safely and properly sprayed. Homeowners have several insecticide options to choose from. Insecticides containing the active ingredients BT (Bacillus thuringiensis subsp. Kurstaki) or Spinosad are both good options to minimize damage to beneficial insects. These are effective when caterpillars are small. Spraying at the first sign of webworms is recommended.

Other sprays which are effective include insecticides containing the active ingredients acephate, carbaryl, and pyrethroids such as bifenthrin, permethrin, cyfluthrin, and zeta-cypermethrin. The key to controlling caterpillars is good coverage and a spray forceful enough to penetrate the web. Make sure to follow insecticide label directions to minimize damage to beneficial insects and the environment, including yourself.

While doing nothing to control fall webworms is often the most common approach, there are several control options for homeowners. Controlling populations can reduce the number of webworms in the fall.