Leopard moth (Zeuzera pyrina) - stem-boring larval damage to olive

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MikeHardman

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I have a small olive tree (2m tall), which was not very healthy. It was also in the wrong place, so I moved it. It moved OK and is showing some new foliage now, but because there is still relatively little foliage, I was able to see numerous stem-borer holes. I am pretty sure these are caused by the larvae of Leopard moth (Zeuzera pyrina). But I'm not sure what to do...
Some of the affected stems are not much fatter than the larval holes (see last photo), so they will be physically weak. So I am happy to prune them off. But where to draw the line with the pruning? There are also larval holes low down in the main trunk. The photos show the holes in a range of trunk sizes.
It would be nice to save some of the structure of the tree. Can I prune lightly and treat the tree to protect it?
Or should I cut it back to a stump and let it regrow, gradually building up a new structure?
Other suggestions?
(Note: the last photo shows the whole extent of the gallery - much shorter than I expected. The hole to the outside is at the bottom of this photo; I presume that is an exit hole.)
Mike
Geologist by Uni training, IT consultant, Referee for Viola for Botanical Society of the British Isles, commissioned author and photographer on Viola for RHS (Enc. of Perennials, The Garden, The Plantsman).
I garden near Polis, Cyprus, 100m alt., on marl, but have gardened mainly in S.England

David Bracey

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Re: Leopard moth (Zeuzera pyrina) - stem-boring larval damage to olive
« Reply #1 on: October 13, 2011, 09:43:52 PM »
Mike ,this is new for me so I looked it up on Wikipedia...................http://fr.wikipedia.org/wiki/Zeuz%C3%A8re_du_poirier

Are they like witichy(?) grubs in which case you could farm them.  From the look of the holes the damage may already be done.  I would cut out the infected branches to below the entry hole; you should be able to see the caterpillar if it has not departed, and then burn the prunings.

Wikipedia recs Bacillus thuringiensis presumably against the larvae but how do you get it into the tree.  Can you get hold of some imidacloprid and scatter it round the base of the olive.This is systemic and may do the job.

It may be that you just have to give your olive a haircut but I`m not sure what to do about the next adult generation, sticky traps, pheromones for the moths.  What do the locals do?
MGS member.

 I have gardened in sub-tropical Florida, maritime UK, continental Europe and the Mediterranean basin, France. Of the 4 I have found that the most difficult climate for gardening is the latter.

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MikeHardman

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Re: Leopard moth (Zeuzera pyrina) - stem-boring larval damage to olive
« Reply #2 on: October 14, 2011, 07:22:15 AM »
Thanks David,
Certainly some of the damage is already done. I don't know if any of the holes have occupants; I will investigate...
The problem with systemic pesticide is that the grubs eat central part of the wood, which I am guessing doesn't see much circulation? On a small tree, I suspect it could be more effective to find all the holes and treat them individually somehow. I will try to find out what the locals do (both cure and prevention) - good idea.
Mike
Geologist by Uni training, IT consultant, Referee for Viola for Botanical Society of the British Isles, commissioned author and photographer on Viola for RHS (Enc. of Perennials, The Garden, The Plantsman).
I garden near Polis, Cyprus, 100m alt., on marl, but have gardened mainly in S.England

David Bracey

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Re: Leopard moth (Zeuzera pyrina) - stem-boring larval damage to olive
« Reply #3 on: October 14, 2011, 08:23:58 AM »
Mike find the holes and squirt an aerosol up it.  Any synthetic pyrethroid will do.
MGS member.

 I have gardened in sub-tropical Florida, maritime UK, continental Europe and the Mediterranean basin, France. Of the 4 I have found that the most difficult climate for gardening is the latter.

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MikeHardman

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Re: Leopard moth (Zeuzera pyrina) - stem-boring larval damage to olive
« Reply #4 on: October 14, 2011, 05:15:08 PM »
Will co', David. Thanks.
For reference (for me as well as anybody else), here's a detailed factsheet on synthetic pyrethroids -
http://www.beyondpesticides.org/pesticides/factsheets/Synthetic%20Pyrethroids.pdf
Mike
Geologist by Uni training, IT consultant, Referee for Viola for Botanical Society of the British Isles, commissioned author and photographer on Viola for RHS (Enc. of Perennials, The Garden, The Plantsman).
I garden near Polis, Cyprus, 100m alt., on marl, but have gardened mainly in S.England

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MikeHardman

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Re: Leopard moth (Zeuzera pyrina) - stem-boring larval damage to olive
« Reply #5 on: October 15, 2011, 07:30:57 AM »
Interim update/thoughts:

I have pruned back the branches that were almost devoid of foliage, and examined the holes in those branches. All holes are about 60mm long and 5mm in diameter, ie. none of them extend into big galleries. They are also consistently in the centre of the branch, which probably leaves the branch with the greatest strength (it is a tube). All holes were empty.
The holes one sees on the outside are the same diameter as on the inside, so I am sure these are exit holes. ...or I would be if I had found a pupa inside. Having made the chamber, it would seem likely the moth would use its protection and pupate there. That's confirmed by this diagram (figure D). Maybe the larvae were extricated by a predator of some sort (we don't have aye-aye in Cyprus!) Note that, in figure D, the pupal exit hole is at the top of the tunnel; none of the tunnels I have seen come out at the top. That may be consistent with predation at the larval stage.
...
Some pieces of the jigsaw don't seem to fit, yet...
Even if the larva was lost to predation, how come the hole on the outside is the same diameter as that inside? The larva must have chewed it out to that size. (The larva emerges from the egg laid near a leaf bud and bores through the bark when very small - so the entrance hole is tiny.) I can see that would be a good idea - to let its crass (faeces) fall out. So maybe that figure D is misleading; maybe the last chewing the larva does is final enlargement of the entrance hole, then after pupation and metamorphosis, the adult emerges from the pupa downwards (assuming it can turn around). And then maybe the remnants of the pupal case fall out - leaving the empty tunnel. That scenario would also be of benefit since rain water would have no chance of entering the tunnel.

Interesting little conundrum.
Still pondering...

« Last Edit: October 15, 2011, 09:30:46 PM by MikeHardman »
Mike
Geologist by Uni training, IT consultant, Referee for Viola for Botanical Society of the British Isles, commissioned author and photographer on Viola for RHS (Enc. of Perennials, The Garden, The Plantsman).
I garden near Polis, Cyprus, 100m alt., on marl, but have gardened mainly in S.England

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MikeHardman

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Re: Leopard moth (Zeuzera pyrina) - stem-boring larval damage to olive
« Reply #6 on: October 15, 2011, 09:24:20 PM »
Here's a photo of a much smaller stem-borer hole (with one of the normal sized ones for comparison). I can't say the small hole was made by a leopard moth larva, but it demonstrates the idea. My worry is that most of the larva's existence may be within the wood before it makes the larger-sized hole - in which case it will be much harder to find the right holes (holes with occupants) to prod with David's wire.

Note:
- If you look slightly to the right of the tiny hole, you'll see a slight change in colour of the twig - showing where the twig has died back to
- the scale is mm
« Last Edit: October 15, 2011, 09:28:00 PM by MikeHardman »
Mike
Geologist by Uni training, IT consultant, Referee for Viola for Botanical Society of the British Isles, commissioned author and photographer on Viola for RHS (Enc. of Perennials, The Garden, The Plantsman).
I garden near Polis, Cyprus, 100m alt., on marl, but have gardened mainly in S.England

ezeiza

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Re: Leopard moth (Zeuzera pyrina) - stem-boring larval damage to olive
« Reply #7 on: October 16, 2011, 02:54:12 AM »
Besides other available methods, a syringe with its needle and a small amount of formaline or turpentine applied well inside the tunnel will do. Immediately after applying seal the hole with some plasticine, or chewing gum, dough, etc.