The Fall Webworm

August 24, 2012

IN LATE SUMMER, it’s fairly common to find weird-looking webs (like the one pictured above) on crabapple and other hard-wood trees. Who weaves these horrid things? Meet Hyphantria cunea, the “Fall Webworm.” More about this caterpillar, and why you needn’t go out on a limb to eradicate it:

Hyphantria lives a well-protected life in the silken, water-proof tent it spins around the leaves it eats. Birds and parasitic wasps are rarely able to penetrate the tents. As the caterpillars require more foliage, they simply expand their tent until an entire branch is enclosed.

What do I do about this furry worm? Basically nothing. You see, here in the Northeast, the webworm emerges only in late summer or early fall. Trees at this time have already prepared themselves for winter dormancy, and couldn’t care less if they have leaves or not. They always recover without a hitch the following spring.

However, the webs are unsightly. To remove them, I either prune off the effected limbs, or sweep the webs with a broom or a stick. As the web comes off the tree, the caterpillars remain attached to it. Webs and their inmates are then disposed of.

Again, you need only remove such a tent for aesthetic reasons. If permitted to live, the colony will feed for 4-8 weeks, then migrate downward and pupate in the soil. In spring they will emerge as dusky-white nocturnal moths.

Their are two races of Hyphantria: blackheaded and redheaded. I have the blackheaded type. Both have yellowish bodies. The black dots on their tent are from the waste they produce.

Have you seen the tell-tell signs of the Fall Webworm in your garden? You can let me know in the comments field below.

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Related Pest-Posts:

When Not to Kill a Tomato Hornworm
How Do YOU Deal with Critters?
Got Weeds? Use Vinegar, Not Round-up

Comments

  1. Eric says:

    Yes, I have these webs on a great big crabapple tree in my backyard. In the past I've sprayed them to no avail. But if the web is waterpoof, that explains why the spray didn't work.

    Good to know I don't have to do anything about them.

  2. Adele says:

    Kevin you read my mind: I've been wondering about the webs that appear on my apple trees every few years. Someone told me it was the Eastern tent caterpillar, but they are springtime pests, right? Has to be the fall webworm you described.

  3. Eric – yes, sprays are mostly ineffective on these pests in their tightly-woven quarters. Even birds and wasps are thwarted by the webbing.

    Adele – Eastern caterpillar emerges in spring, and can cause real damage them. The fall webworm is basically harmless. I remove nests purely for aesthetic reasons. (And in truth, I don't kill the worms — just relocate them to the forested area of my property).

  4. Anonymous says:

    Web worms are a favorite of bats and black- and yellow-billed cuckoos. Leave them for the wildlife.

  5. Anonymous – that's good to know. I've left most of mine them in place.

  6. Averasha says:

    I am a kid who found a cute little web worm today I am keeping it for a pet thank you for teaching me about them.

  7. Annie says:

    Thank you for saving me from certain disaster!

    I found some wicked looking bug-tents hanging in my trees. Everybody I know has something ugly to say about it – they’ll kill every tree in sight! they’ll multiply so fast they’ll infest your entire garden within a week! the only way to get rid of them is to burn them out with kerosene after dark on a moonless night!

    I arranged for a couple of people to come tomorrow and help me with this. My plan was sketchy at best, mostly a few half-formed ideas involving a saw, a tarp, some rope, extra-hefty garbage bags . . . oh, and hats, very large hats, in case those tents burst open over our heads. I figured maybe I’d better do a little research tonight.

    And that’s when I found your article. Now we can leave the paraphernalia in the shed and sit around on the deck all day, sipping something fine, and talking about subjects far more pleasant than sticky tents filled with wiggly webworms! Bless you!

  8. Averasha – Nice to meet you.

    Annie – You are right. Much better to sit around drinking wine than to worry about tent caterpillars. The pests attacked two of my crabapple trees late last summer. Both trees resumed their normal beauty the following spring.

  9. I have also these webs in my home garden and I want to remove them. But how I do not know?

  10. GDRR -No need to remove a web except for the sake of appearance. As I mentioned in the article, you can use a broom to remove a web. A power-washer should work, too. Otherwise you’ll have to clip the branch, which will alter the shape of your tree. Again, the caterpillar is only a temporary nuisance; the tree will resume its normal beauty in the spring.

  11. Meg says:

    When I was a kid we used to burn them out of our crab apple trees using long cones of rolled up newspaper – though I don’t know if it was for aesthetics or out of ignorance. I have never bothered on my own property and wouldn’t use an insecticide. So glad to know that my instinct was right! Great post. Thanks.

  12. Candy says:

    It seems to me the trees mostly mentioned here are fruit trees. I have a nice condo of webworms forming in some redbuds. Coudl these be something else or are all of the webs inhabited by the same type of pest?

    Thanks,
    Candy

  13. Hi Candy – The webworm can inhabit any hardwood tree, including redbud. No need to do anything about it — your tree will resume its usual beauty next spring.

  14. Patricia says:

    Kevin,
    Are Fall webworms different from regular tent caterpillars. I have had an infestation this summer on an evergreen bush and it appears to have killed much of the foliage. These are the ones that hang on the bush in a cone shape and don’t actually leave tents. HELP! Thanks, Patricia

  15. Hi Patricia – From what I know, tent caterpillars make their tents in the spring, just as trees are leafing out. Webworms make their tents in the fall. Both types feed on deciduous trees, not evergreens. The fall webworm is annoying, but its damage is only temporary.

  16. samantha says:

    i love these fall webworms cause they r the most fun insects 2 capture and feed and take care of

  17. Val says:

    I’ve been cutting webworms out of my Yoshino Cherry trees for years. Every year I cut out at least 20 to 30 webs. I try to get them when the webs are very small so I don’t have to cut as much of the branch. I felt that if I let them pupate in my soil I’ll be overrun by them in the future. I don’t see any of my neighbors having any webs in their trees. They love the cherry trees though. I think it’s about late July, early August when I see the first of them.

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  19. Dana Freeman says:

    Hey Kevin,
    What do you suggest for killing ants? They have taken up colony all over the place on our property and in flower beds, along edges, etc…

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  21. Kathy Baker says:

    Hey Kevin I have a question about webworms,is it true that the more of their webs you see in trees it tells you what kind of winter you’ll have?

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