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Honey Locust Mimosa Webworms...HELP!

Posted by viche 7a MD (My Page) on
Sat, Aug 21, 10 at 10:59

I've seen Mimosa Webworms (visual confimration) in my honey locust over the past few years and haven't done anything about it. This year, a decent portion of the leaves (65%?) are webbed and truning brown. I'm in MD. The tree is about 20 years old.

Oh, also, there are these webs hanging all over the tree all the way down to the ground. It looks like a friggin Halloween tree at this point. Are these from the worms or from predators?

I found this link:

They suggest:

"Prune out and destroy small infestations within easy reach. If a large percentage of the tree is affected, that is not practical. Since mimosa webworms are moths, Bacillus thuringiensis (Bt) provides excellent control of small larvae. Once they grow to a larger size, over one-half inch, Bt will not be as effective. Other insecticides labeled to control mimosa webworm include BioNeem (azadirachtin); Sevin (carbaryl); Bayer PowerForce Multi-Insect Killer (cyfluthrin); pyrethrins and piperonyl butoxide; and Captain Jacks Deadbug Brew (spinosad)."

Too much to prune at this stage

One worm on a lower branch waS 3/8" - 7/16" long.
This is obviously the second generation of worms sicne it's August. They are pretty well protected inside their webs.

Do you think Bt would work at this stage or should I just wait until next year?
Can I purchase and apply it myself?
Is Bt something that the tree absorbs or something that I need to get all over the leaves?

Are any of the other solutions listed in the article above non-toxic to humans?

Any other advice would be welcome. :)


Follow-Up Postings:

RE: Honey Locust Mimosa Webworms...HELP!

  • Posted by jean001 z8aPortland, OR (My Page) on
    Sat, Aug 21, 10 at 14:13

Bt won't work if inaccessible to the worms.
Perhaps you can disrupt a number of the webs with a long-handled tool, perhaps a broom or a length of PVC.

RE: Honey Locust Mimosa Webworms...HELP!

The tree is 30 feet tall. The webs are mostly in the upper branches. If you've never seen them in person, the webs actually bind a number of leaves together. So unless you use your fingers, you can't get at the worms. These aren't like tent catepillar nests where the webbing is visible. The webbing is almost like a glue that holds the matted brown leaves together protecting the worms.

So should I wait until next June? Quesiton is, how do I know when to spray? I can't see the tiny worms up there. All I see is the matted brown leaves that appear after the worms are well established.

RE: Honey Locust Mimosa Webworms...HELP!

You could always call a tree service and have their tree expert look at the problem.
You are going to have to do that anyway, if the tree is 30 feet tall.
Or let it go and see if the tree survives, it needs it's leaves after all.

RE: Honey Locust Mimosa Webworms...HELP!

I guess I do need to call a tree company.

I was hoping to avoid that. They always want to charge an arm and a leg to pour some toxic substance on the roots that will systemically kill every living thing that touches the tree, and that turns leave piles in the fall into toxic mounds.

I thought that I might be able to hit the top of the tree with a hosed based spray.

How long do trees need there leaves for? It's almost September. According to the University sites, Mimosa Webworm on a Honeylocust is just a cosmetic issue. Bit like it being "only a flesh wound."

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