Unfortunatly in the research that I have done I have discovered that there is no way to make a selective media the will prevent the growth of Trichoderma. The problem is that it is a parasitic fungi so it feeds off other fungi. Allthough I was not able to come up with a selective media because of this I did however run across this patent application for something that will work in preventing the growth of green molds and also reduce/eliminate current infestations unfortunatly I do not have access to the proper supplies to test this any more. But it is a start if anybody has access to what the patent calls for I am sure they can get it working doesnt seem too complex.
http://tasteslikeachamp.com/Green_Mold_Inhibitor.docx (http://tasteslikeachamp.com/Green_Mold_Inhibitor.docx)