You shouldn't find Trich sp. inside stipe or cap tissue, but you will regularly find pseudomonas which can be easily cleaned up with amp. I also wipe down my specimens with h2o2 and tear them open rather than cutting. This is important because often contaminants can be introduced into the the tissue by the knife as it passes through the 'dirty' surface layer. Also, where is the contamination popping up? If at the inoculation site then this would be consistent with specimen contam, but if elsewhere then maybe your plate wasn't sealed? With love, Mimz