Wood worm - is it dead yet

[Lazurus]

Just moved into our new place and I cleaned out the single garage that the old boy before us had used as a small workshop. I noticed some active woodworn in the rafters (flat pent roof) so I gave it a good dose of Cuprinol wood worm killer 5 days ago. I noticed today there is still some active critters in the wood. Do I need to reapply or will the original spray act on and kill thos still munching?

 

[MikeG.]

Keep on going with the poison. They go through stages of their life-cycle fairly quickly, and you may have killed the larvae but missed some eggs, for instance, which have since started munching.

What's the state of the wood? If you poke around with a screwdriver or bradawl, do you find soft stuff? I presume the timber is untreated, is it?

 

[Lazurus]

Keep on going with the poison. They go through stages of their life-cycle fairly quickly, and you may have killed the larvae but missed some eggs, for instance, which have since started munching.

What's the state of the wood? If you poke around with a screwdriver or bradawl, do you find soft stuff? I presume the timber is untreated, is it?

Timber all looks sound and dry, just the critters, I will give them another dose of the good stuff and await the results.

 

[Ttrees]

Guessing the hidden parts of the rafters would be the most difficult to decimate furniture beetle, especially if there is a large amount of sapwood in those areas.
What's the procedure for doing these awkward bits, would tenting, covering or wrapping with plastic be more efficient with the permethrin solution?

Sounds like the place is or was a bit on the damp side, hopefully just from being jam packed full of clutter, or having maybe some other issue that's since sorted?

 

[Richard_C]

Persistent little things, keep an eye out, you may even need to treat again after a few weeks/months - depends how well the treatment has soaked in. It does work though, I did similar in a new (to me) garage about 40 years ago and the roof survived our tenure and beyond.

According to the myth, when Noah was doing his species-saving gig and letting all kinds of things two by two onto his arc - even some big and scary carnivores - he drew the line at woodworm. "Sorry mate, far too dangerous to let the likes of you on board. Dunno how long this wooden arc will have to last".

But of course he didn't have modern insecticides.

 

[Chrispy]

I'm pretty sure that the worm fluid you use does NOT kill the worm, it only kills the new laid eggs and sterilizes the adults as they eat their way out thus breaking the breeding cycle.

 

[Sgian Dubh]

I'm pretty sure that the worm fluid you use does NOT kill the worm, it only kills the new laid eggs and sterilizes the adults as they eat their way out thus breaking the breeding cycle.

That's not quite the case Chrispy. The typical common furniture beetle treatment fluids are permethrin therefore they are contact pesticides affecting the nervous system and kills them. The stuff passes through the insect's cuticle or shell. It kills only those insects it comes into contact with. It does not kill through, for example, the mature grub chewing a hole to emerge because they're not feeding to do so, but it will kill if the emerging insect's shell scrapes along treated wood. Nor does it kill mature insects laying eggs, although it does rather discourage them from doing so, and it will kill the larvae as they emerge from the egg, if they come into contact with the permethrin.

Flooding treatments with permethrin can't penetrate deeply into the wood, no more than maybe a couple of millimetres, but possibly (very rarely I'd say) up to three to six millimetres if the material is especially absorbent. Immature grubs that come into contact with that treated wood near the surface will be affected, but not those deeper in where the poison cannot reach them. Treatment relies entirely upon repeated dosing that rub against the skin (if that's the correct term) as the grubs pass by or, as already mentioned, as they emerge as adults; the immature grubs can spend anywhere between two to five years maturing, meaning treatment has to be repeated over a number of years, especially during the spring and early summer period when the grubs emerge as adults. Slainte.