Aaron wrote

> Both Trevor and Nick point out that CCA treated lumber should be painted.
> Do either of them know whether specific guidelines as to quality and type of
> paint were developed?
>
> Comments regarding grade and type of paint used in the field would be
> appreciated.

Have checked with our wood chemists and it seems that it does not matter what type of paint is used.  The main criterion is that the timber must be drier back to equilibrium mositure content (EMC) which is what the moisture is in the surrounding air.  This is normally in the range of 12 to 15% but can be lower in areas of very low humidity e.g desert areas.

If the timber is dry to EMC then any paint type should not allow the CCA to come through.  This is provided the paint surface stays intact and the bees do not chew it off and expose the treated surface or wear it off in areas such as entrances where the traffic of bees can remove paint and timber.

I was also told that there is a chance that CCA may not be around for too much longer.

Nick quoted some research in New Zealand on CCA.  The full reference is:-

Danger of Using Arsenic Treated Timber for Beehives by D.L. Harrison, T. Palmer-Jones and R.G. Nairn  New Zealand Journal of Agriculture Vol. 98 (4) pages 338-9, 1959.

This work was done by only painting the outside of the boxes and leaving the insides as is.  The timber was dried and in one trial was even treated rough, dried and dressed.  It would seem there was no painting of the inside to see what effect this would have.

Looking back on my own notes, I saw where in lectures to beekeepers we were recommending that they do not use CCA for any hives parts that may be accessed by bees.  This would leave only the botom cleats on hives and other things such as hive stands.  This is in line with what Nick posted.

Trevor Weatherhead
AUSTRALIA