Termites CAN eat pressure treated wood.
More Info: Though pressure treated wood may discourage termite infestation, it does not prohibit it. Termites will attack pressure treated wood through the ends, any cracks and fissures, and will also build tunnels on top of it.
Pressure treated wood is poisonous to insects, bacteria, and fungi so it will discourage new colonies from forming, but keep in mind that like anything else pressure treated wood will deteriorate over time and exposure to the elements leaving it susceptible to the same assailants as any other lumber.
Potter, Mike, and Extension Entomologist. “Protecting Your Home Against Termites | University of Kentucky Entomology.” Learning, Discovery, Service | in the College of Agriculture. N.p., n.d. Web. 17 Nov. 2011. http://www.ca.uky.edu/entomology/entfacts/ef605.asp
“Termites Management Guidelines–UC IPM.” Home Page – UC Statewide IPM Program. N.p., n.d. Web. 17 Nov. 2011. http://www.ipm.ucdavis.edu/PMG/PESTNOTES/pn7415.html