Sorry i wasnt very constructive there . Blue stain as i know it has no structual effect on the timber and is only found in pine . It is a fungus that attacks the sapwood and feeds on the sugars in the timber and ray cells if i remember rightly ..... It was along time ago ......Bluestain is not regarded as a defect in the timber as all it does is make the timber look blue . The staining in the Hardwood ply shown looks more to me like the start of wet rot .