First Aid for Your Trees, Servicing the Greater Tampa Bay Area

What are those cobwebs in my tree?

Trees are a crucial part of every landscape, as they provide shade from the sun, food, and oxygen along with numerous other benefits. One of the primary reasons so many people love trees, is the added aesthetic quality they bring to the landscape. So, when one notices unsightly cobwebs covering the leaves of their favorite tree, it is not unreasonable to have some questions. Not to worry though, today we are going to discuss what critters cause those unsightly cobwebs and what you can do to rid your trees of them.

What type of insect is build webs in my trees?

There are two different insects that build webs within trees, the Fall Webworm and the Eastern Tent Caterpillar. The most efficient way to determine which one of these pests has made home in your tree is by observing the season, in which the webs are present. These too insect pests are both a type of caterpillar, can be found in North America, and are well known for spinning their webs in trees. However, despite these similarities these two caterpillars have very distinct differences.

green fall webworm with many tiny hairs sticking out all down the body and is laying on a green leaf
Katja Schulz from Washington, D. C., USA [CC BY 2.0], via Wikimedia Commons

Fall webworms are small caterpillars, that are approximately 1-inch in length with a yellow-green striped body, that is covered in gray-orange hair. The Fall Webworm is native to North America, they emerge from their winter cocoon as a moth in the summer and after finding a host tree, they build the web for protection and begin eating while safely tucked away inside their

The Fall Webworm can be found grazing on several different tree species including, but not limited to: the birch, willow, maple, pecan, cedars, and persimmon. Fall Webworms eat on the leaves, or foliage, of the tree and once their food source has dried up in one area, they will move on to another section of the tree. Working their way throughout the tree, eating on the leaves; the more they move, the more webbing you will notice.

the web of a fall webworm covering the leaves and branch of a tree
group of black eastern tent caterpillars with a white line down its back with blue dots and they covered in tiny hairs covering the branch of a tree
J.R. Carmichael [Public domain], from Wikimedia Commons

Eastern Tent Caterpillars are a species of moth and are most commonly found in the eastern and central U.S. In comparison to the above Fall Caterpillar, these caterpillars are slightly larger, reaching lengths up to 2 ½-inches. The Eastern Tent Caterpillar, though not what it is best known for, has very distinctive markings. The caterpillar is all black with a bright white line running down it’s back and visible orangish hairs along its sides. If you observe the caterpillar closely you will notice it also has brown and yellow lines along its sides, further accented with light blue spots.

The Eastern Tent Caterpillar hatches in the spring time and enjoys feasting on the foliage, or leaves, of fruit trees such as: wild cherry, apple, crabapple, peach, and pear trees. This particular type of caterpillar is very well known for it’s unique “tent” like web that is strung in the “crotch” of trees, this is the point where the branches meet the trunk. They prefer to be inside the tent when its cooler, like at night time or on a cloudy day.

White eastern tent caterpillar cobweb covering the brown tree branches where they meet the trunk
Photo by Greg Hume (Greg5030) [CC BY 2.5], via Wikimedia Commons

Will Fall Webworms or Eastern Tent Caterpillars harm my tree?

Typically, these insect pests are merely an eye-sore, as their webs are commonly considered aesthetically displeasing, and do not cause any real harm or long-term damage to the tree. The Fall Webworms spin their webs towards the ends of branches; therefore, the webs can be easily removed by knocking them down with a broom. The same is true for the Eastern Tent Caterpillars, their webs can simply be removed, from the crotch of the tree, and disposed of.

Although, these pests are generally not harmful there are some instances where the invasion of these pests is of concern.

Newly Planted Trees

Newly planted young trees, that are not yet established, can not handle the stress of having their foliage eaten by these critters. The caterpillars can cause severe leaf loss within a newly planted tree, causing the tree to become stressed. This could result in total loss of the newly planted tree. If you should notice these webs popping up on newly planted trees, contact your local arborist right away to have the webs and insect pests removed.

Severe Infestation

Healthy established trees that experience minimal to moderate leaf loss, or defoliation, that is spaced out over the years are not high risk. However, a severe infestation of either of these insect pests, that results in severe defoliation over consecutive years will cause the tree to become stressed. Stressed trees are more susceptible to other insect pest infestations and diseases; which in turn could result in the death of the tree.

How to treat these insect pests infestations?

Now that you know what is building those unattractive webs in your trees, you probably want to know how to get rid of these insect pests. As stated earlier you can simply remove the unsightly webs from the tree and destroy them. However, if you wish to rid the tree of the caterpillars, have a newly established tree that is infested, or have a severe infestation you will need to contact your local arborist.

Caterpillar populations are generally well controlled by natural factors such as weather, natural predators, and diseases. However, on occasion we do see outbreaks. When this happens, your local arborist will come out to asses the infestation and determine a treatment plan. Treating caterpillar infestations typically includes pruning away any small branches that may contain eggs, as well as, removing and destroying their webs. Your arborist will also recommend a treatment option for controlling the pest population throughout your landscape, whether it is an insecticide or Integrated Pest Management control. Depending on the amount of foliage loss, die-back, and thinning found in the crown of the tree additional treatment may be needed to help the tree recover and promote new health growth.

Insect pest infestation in Hillsborough County, Tampa? Tree Medics arborist is highly trained and educated in insect pest removal and holistic tree care. So, give us a call at (813) 407-9974 to schedule an appointment, or message us.

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