What insect produces this web on trees ?

hogue

Over the past week or so I have been seeing parts of young trees enclosed by a dense web - like a spider's web - see the attached photo. It reminded me of a trip to Vermont and New Hampshire last year where I saw many trees affected this way.

I have read somewhere that the Ermine moth produces this kind of web here - to protect its caterpillars who proceed to defoliate the enclosed part of the tree. I also seem to recall that the ermine moth has preference for spindle trees (Euonymus ??) and I havent seen any spindle in the immediate vicinity.
The attached photo shows web on young Scots Pine and other species (Ash, Birch) growing nearby are also affected - as are some of the stakes supporting the young trees.

I havent seen any caterpillars in the web but there are many small spiders on the outside - perhaps they are visitors or predators rather than the producers of the web.

Any ideas on the cause and/or the effect it is likely to have on the trees ??

Greengage · Posted: Thu May 24, 2012 8:01 pm Post subject:

I dont know where you are but check out the processionary caterpillar http://web.cortland.edu/fitzgerald/PineProcessionary.html

hogue · Posted: Thu May 24, 2012 9:25 pm Post subject:

Thanks Greengage,
I will follow those leads and i may come back to you for further info. It was in Kildare that I saw the "webbed" pines.
Thanks again.

Greengage · Posted: Fri May 25, 2012 1:34 pm Post subject:

now im curious exactly where and I will go look

hogue · Posted: Thu May 31, 2012 8:32 pm Post subject:

I went back to look at the webs this afternoon - it had been raining for several hours at the time. Most of the webs that saw last week have now more or less disappeared although remnants can be seen on the pine trees.

I looked for signs of life in what remained of the webs but did not find anything - no caterpillars and no sign of the small spiders that I had noted earlier.

i will keep an eye on the trees and let you know if any webs re-appear.

Greengage · Posted: Thu May 31, 2012 8:44 pm Post subject:

Ive linked the post to a number of friends no reply yet, still curious
Put it under whats this plant and silver surfer may know

inishindie · Posted: Fri Jun 01, 2012 2:20 pm Post subject:

Interesting stuff....., Greengage mentioned it earlier and my facebook chums seem to agree...Pine Processionary Thaumetopoea pityocampa
Also known as tent caterpillar..Leinster had a lot of them last year...

http://en.wikipedia.org/wiki/Pine_Processionary

Some places have these to try and control them.. http://en.wikipedia.org/wiki/spam

Greengage · Posted: Fri Jun 01, 2012 9:04 pm Post subject:

im really interested in your views that Leinster has processionary caterpillars
are you sure I would love to know where and when because as far as im aware it has not arrived yet.
This is a serious nasty piece of work if you can verify it has arrived I wouldd like to know where, My sourses are still on the case. the only thing that kills it is hairspray and you will get a rash from the caterpillars.
please post more.

inishindie · Posted: Fri Jun 01, 2012 9:11 pm Post subject:

I'll check with the lad in Leinster. I think that they might be spotting the spiders webs on hedgerows on misty mornings...I'm looking into it...

hogue · Posted: Fri Jun 01, 2012 11:43 pm Post subject:

Thanks folks,
I will be interested to hear more about processionary caterpillars in Leinster - having being alerted to them I have been discovering that they are, indeed, nasty beasties

Greengage · Posted: Sun Jun 03, 2012 2:55 pm Post subject:

Ok you made this hard and I had to do a lot of work but at last I have an answer
This web is created by the webber moth a close relation of Thaumetopoea pityocampa or Tent Catterpillar which comes from North America.
I gogled it when I believe thats what it is an Peter Donegan had an article which ive linked here.
http://blog.doneganlandscaping.com/2010/06/02/webber-moth/
This should earn me a few brownie points.

kindredspirit · Posted: Sun Jun 03, 2012 5:17 pm Post subject:

Are you sure it's not an Ermine moth?
Usually defoliates hawthorn but also infests pine trees.
The small caterpillars have grey and brown bands.

Greengage · Posted: Sun Jun 03, 2012 5:48 pm Post subject:

No im not sure but on the info posted here and my sources Im sticking with Webber moth until proven otherwise, If it is seen again post on the site and I will go look and collect caterpillars for positive ID.

hogue · Posted: Sun Jun 03, 2012 8:06 pm Post subject:

Thanks folks,
I appreciate your help and the suggestions.

I am relieved that Processionary Moth has been taken off the list of "possibles" but I am troubled by the fact that I have not seen any caterpillars in any of the webs. I note that Webber moth caterpillars are 12-15mm long and i feel that I would have seen caterpillars of that size had they been present.

I will be keeping an eye of the trees in that area and if there is a recurrence of webbing I will post it.

Thanks again for all of your help.

mothman · Rank attained: Hazel Tree Joined: 13 Dec 2006 Posts: 10

I was alerted to this thread by a colleague. In my opinion this web is not caused by caterpillars, for a number of reasons.

There have been no caterpillars sighted,
The web disintegrated in the rain. Caterpillar webs are not that delicate
I am not aware of pine being a foodplant for any of our web producing moths.

There are a number of moth species that produce webs or tents. Ermine moths were mentioned above and some of these can produce very extensive webs and a colony may defoliate 10s of metres of hedgerow. It is these that often make the news. There are 5 species of these ermine moths known in Ireland. They look very similar as adults, but can be identified by foodplant and nature of web. 2 of the species use Spindle, another uses Apple, another usually Hawthorn or Blackthorn and the other Bird Cherry.