Masonry bee structural damage / in cavity wall by eating area

[peteuk]

Hello all,
I wish I had found this site last year when my 1st bee concern arose - strangely it didn't come up - maybe because I searched for 'masonry' or 'solitary' bees.
Anyway hopefully someone can reassure and advise me.
I've read the other points in this forum and don't follow it all though I do feel better after reading it.
1st a bit of history:
We bought our bungalow about 3.5 years ago and in the 1st summer discovered wasps going though an airbrick into a South facing cavity wall / underfloor space. The Council duly came and sprayed the airbrick - problem solved.

Last year we noticed what I took to be masonry bees flying in to the same cavity wall via holes left following satellite dish removal.
I remember seeing a UK TV program (a long time ago) which showed how masonry bees (I think) had dammaged the structure of a house and the advice being to get rid of them.
UK advice on the net seemed to be leave alone. But sites from other countries (eg Canada/Australia) was that the comb and honey can cause damage, and that masonry bees can cause structural failure due to undermining the mortar.
We left alone and eventually the bees filled up the holes in the wall with a 'cement type' structure. I expected them to appear again this year.

Now the bees are back (same ones?) but they are not using the holes they sealed last year. They are using the same airbrick that the wasps originally used. Unfortunately this is right beside the table we use on the patio and people are too nervous to sit there (despite my reassurance after reading your site).

Questions:
1). Can I be sure the bees will do no harm to my house?
2). Can I be sure the bees are not a threat to anyone including young children even if eating in the area.
3). Can I discourage them? I do not want to kill them only to find we then have another wasps nest in its place which seems to be a possible danger. (Sealing the airbricks - there are 3 - does not seem to be realistic: they are there for a reason. If the bees are no threat whatsoever I do not mind them using the cavity say if they reverted to their old entrance via the now blocked satellite dish holes. These are higher up the wall and not near where people regularly sit).

Your reassurance and advice will be gratefully appreciated - thanks.

[RoofTops]

It sounds as if they are mason bees but there other sorts of bees - can you see them carrying any bits of leaf into the nest?

Assuming these are not honey bees which have set up home in your cavity wall (a bad thing) then if the bees are building nest holes in the air bricks with mud they are mason bees and eventually they are going to fill the brick up completely. I would suggest offering them an alternative nest - you can buy them from garden centres and once they start using it you could block up the air bricks in a way which still allowed air to circulate but kept the bees out. Either fix some plastic mesh over the air bricks - greenhouse shading would work or fill the holes in the air bricks with short lengths of plastic drinking straw - too small a diameter for the bees but OK for air circulation.

The bees won't sting anyone but some people will be nervous of them so re-locating them will be best.

PS: If you do get bees nesting in the drinking straws let us know - they could be something interesting!

[peteuk]

Hi RoofTops,

Thank you for the quick response.
I've tried to photograph the bees but they're too quick for me - I have a synchronisation issue with the digital camera. But I think they are masonry bees because of what they did last year.

The bees don't seem to be blocking up the airbrick so I assume they are nesting elsewhere within the cavity (I thought I heard a bee like buzzing noise from under the floor the other day but this could have been paranoia as I haven't heard it since)

Does anyone know if they could be causing a structural problem?

If I provide an alternative nest, how do I persuade them to move before blocking the air brick off?
If I block it off straight away I assume some bees and larvae would be trapped in the cavity? Will they die or seek another way out - into the house even?

Thanks again

[Chris]

100 years of mason bees excavating mortar might cause 'damage'.

As far as I know they do posses a sting, but it is not sufficiently pointy enough to pierce human skin. And the venom is only weak.

If it were my home I wouldn't care in the slightest whether they are in my wall or not. I would say the chance of a sting is a pretty remote one. But if you want to try and annoy them by blocking off access to their nest holes, that is a surefire way of trying to get them to sting.

If you find out they are honeybees, then the above info does not apply. A sting from a honeybee hurts.

[peteuk]

Assuming I get it to work I have uploaded 2 photos of my bees.

http://www.britishbee.org.uk/forum/picture.php?albumid=22&pictureid=137

http://www.britishbee.org.uk/forum/picture.php?albumid=22&pictureid=138

Can anyone confirm they are masonry bees?
Unfortunately the photos of the bees are not very big but the bees seem to be black with a yellow marking around them.
The yellow marking (IMHO) seem similar to that round a red masonry bee but the body colour is wrong.

Assuming they are masonry bees and I put a mesh of some kind over the airbricks, how do I avoid trapping some in the cavity / entice them to another location.
Because this is a very visible area of the patio, does anyone know of an elegant way to attach the 'mesh' so that it is not an eyesore - I have airbricks all round the house. (Sorry I am not the most practical guy and I can only think of using screws at the moment).

Thanks,

Pete

[ChrisBroad]

It's Red Mason bees. The colour can vary a bit but often its a gingery yellow. They don't damage masonry but just nest in existing holes in brickwork or anything that offers a bit of weather protection. They won't sting you. The flying bees will start to disappear very soon.

If you block the airbricks you will trap some inside but also you will have trapped the whole of the next generation due to hatch next spring. As they are totally harmless to people or property why not just leave them alone?

[peteuk]

Thanks Chris,

If the flying will stop soon I'll leave alone this year.
My concern is the attitude of my wife and others who visit who would like to sit in the garden - they just don't want insects flying about them - specially those that look like they might sting.

My guess is that the bees have used the airbrick because they'd blocked off the holes from the old satellite dish (that they used last year) so this was the easiest way out for them.
The ideal would be for them to go back to their original holes (or other new ones) if I could think of a way of getting them to do that - it's higher up and a few metres away.

I don't want to kill them so I don't really want to seal off the airbrick.

[Chris]

My concern is the attitude of my wife and others who visit who would like to sit in the garden - they just don't want insects flying about them - specially those that look like they might sting.

I would love a garden.