Anne, every packet or bag I've ever had of Trichoderma-based fungus, says quite clearly that it should be incorporated into the potting mix or ground soil, and not sprinkled on top as a top-dressing, as one might do with, say, a bulb food. It seems to need to be dug into the mixture. I suppose it need to get its (metaphorical) teeth into the humus content as soon as possible to become active.