Woodworm treatment

[brightbluesky]

Advice please,
Outbreak of woodworm hatching in floorboards of kitchen corner.
Small piles of dust next to many holes, cleared dust away and more appeared within days so I think it's active.
Lifted floorboards and underside of top varnished board. .. Many many holes almost making board crumble.
Checked under floorboard, no bad smell, no red dust and nothing untoward other than woodworm holes.
Got 2 treatment firms around.
One suggested under board spraying.
The other suggested varnished floors sanded and sprayed both sides.
Which sounds correct and which will be most effective?

 

[vinn]

Are you certain of the full extent of the infection?
Is the board actually crumbly?
Are the boards and joists safe?
Do you have good through ventilation under the floor?
Any damp present in the kitchen or below the floor?

As a DIY'er you can buy a garden spray, and some basic chemicals, and spray it both sides yourself.
You should spray maybe three times in this next year and see how it goes on.
Clear all frass (worm dust) before spraying.
But first the above questions?

 

[brightbluesky]

Are you certain of the full extent of the infection?
Is the board actually crumbly?
Are the boards and joists safe?
Do you have good through ventilation under the floor?
Any damp present in the kitchen or below the floor?

As a DIY'er you can buy a garden spray, and some basic chemicals, and spray it both sides yourself.
You should spray maybe three times in this next year and see how it goes on.
Clear all frass (worm dust) before spraying.
But first the above questions?

 

[brightbluesky]

Thanks for your reply:
This area is the only sign of current activity.
The boards are not so much crumbly as full of holes.
There is an air brick close by but another won't be amiss I guess.
There was some water penetration on external wall but this was remedied two years ago.
You mention spraying on both sides of board but top side is varnished? Is sanding better then spray?

 

[vinn]

Sanding will obviously better allow chemicals to soak in but its not necessary - simply flood the top surfaces and allow the chemical to penetrate "in-situ" worm holes.
FWIW the chemicals, any bug chemicals, only have shallow penetration.
Going under the floor is the best position to spray from.

Examine the window boards of the house looking for accumulations of dead bugs.