If I use treated wood around my fruit trees, will the chemicals poison my fruit?

Wood treated under pressure with Chromated Copper Arsenate (CCA) is resistant to termites and decay, however it does contain arsenic, which is a carcinogenic. You should wear gloves, protective glasses and a dust mask when cutting and handling CCA treated wood.

Some arsenic in CCA treated wood will leach out into the surrounding soil, but it quickly binds to clay particles and does not move far.  Most soils naturally contain some arsenic.  Roots growing near treated wood could absorb more arsenic than usual, but the amount in the fruit from your trees should not be very much, and should not be a significant health hazard.

CCA treated wood is being phased out for residential use.  Other compounds which do not contain arsenic will be used as a wood preservative.  You may be able to obtain wood that is not treated with CCA from a local lumberyard.  You could also use Redwood, which is naturally decay resistant but it can be damaged by termites.