Do Webworms Affect Tree Health?

webworms on a leaf

What are webworms?

Have you noticed these spiderweb looking bags in trees lately, usually toward the end of the branches.  Those are webworms, frequently confused with bagworms, and no, they are not the same.  Fortunately, there isn’t really a webworm treatment, but, so that you don’t just have to look at them, there are ways to get rid of them for this season. That is what we’ll discuss today. 

From June till August, common here in Texas and found all through North America, you’ll find these ugly web bags hanging from trees. This native pest came to us during World War II from Europe. If they are having a busy reproduction season, we’ll see them up through October, such as it is this year, 2020. Arborist and pest control companies alike are inundated with phone calls for webworm treatment.

Natural for this pest, the infestations are sporadic, although some years are back-to-back with webworms. Some years lighter and about every decade or so, we’ll have a back-to-back active years. The type of webworm treatment doesn’t seem to have any effect on whether the next year is busier or not. 

Why are webworms in my trees?

Webworms hibernate as pupae, nesting in cocoons in tree bark or among leaf litter. Then when spring arrives, the adults emerge, deposit their eggs, creating the large webs we see in our trees. 

Webworms are nothing more than a caterpillar that weaves a loose web around the foliage of our trees with their “nest” of larval. They stay there, eating the leaves until they are ready to pupate and multiple more webworms. 

They can go through 11 instars before that happens and the nest can cover several feet, entire branches even and have several nests in one tree. This can stress the tree and definitely results in leaf loss. 

Are webworms bad?

No, they are ugly, but as long as they don’t take over a whole tree, they can’t harm them. Typically, the trees they favor have already stored up the energy they’ll need for winter by the time webworms nest in them. The trees that webworms prefer are: 

  • Ash
  • Elm
  • Fruit Trees – apple, mulberry, pecan, and other fruits
  • Hickory
  • Linden
  • Oak
  • Popular
  • Sweetgum
  • Walnut 
  • Willow

How do you get rid of webworms?

Although webworms are not often fatal to a healthy tree, they are unsightly. When you’ve spent money and time on your landscaping, this isn’t the final piece you want seen. 

When it comes to removing webworms and protecting tree health, early detection followed up by intervention is the best webworm treatment.  This can be done by having the trees pruned when see the start of nests forming. Early detection eliminates the cycle so that the next generation can’t develop.

The best and cheapest webworm treatment is simply knocking them down, bag them up with the trash and throw them away.  You can do this by using a long pole or stick, and even ripping the bags will keep them from reproducing and make them vulnerable to predators that eat worms. 

Of course, you want to be safe. So, if you a lot of webworms in a lot of trees on your property, and they are high up where you can’t reach them safely, then call a professional tree pruning service or arborist.            

How long do webworms last?

Webworm larvae lives approximately six weeks. Annoying to a homeowner, they leave their webs behind and they stay in place until hard, windstorm or snow. You can determine about how long you’ll have to look at them by the color of the web. A white web is a new web. If the web is brown or tan, the larvae has left. 

What will kill sod webworms?

Spring is typically when you’ll start seeing sod webworms. They’re hungry and begin chewing the top of grass, leaving behind brown sod in large areas. Sod webworm the webworms in your trees. 

  • First:  Establish a regular routine watering and fertilizing to enhance your grass’ growth and encourage recovery. 
  • Second: Broad spectrum insecticides is a no-no. It can kill predators that are beneficial. When you first notice sod webworms, using a Bacillus thuringiensis spray is safe. This sod webworm treatment doesn’t work on mature larva, so you need to be watching for early signs and treat right away. 
  • Third: Use a pesticide that is labeled effective against the pests and apply in the late afternoon hours since larva feeds at night. This will ensure the larva will ingest the product and the results are productive. 
webworm web high up in tree

How do I know if I have sod webworms?

Where webworms life in trees on the branches, sod webworms live underground. They will start chewing on the soft tips of your grass and leave behind brown, grazed, or scalped looking spots. They prefer turf grass such as:

  • Bentgrass
  • Bluegrass
  • Buffalograss
  • Fescue – fine, tall leaves
  • Zoysiagrass

What are some examples of webworm infestations? Webworm infestations begin showing up in late summer and can often extend into early fall. They are the sack-web-looking clusters that you see on the ends of tree branches, growing up the branch. Need help with webworms in Fort Worth, TX? Call 817-882-6499 today!