October 2014 issue of the Cornell Flower Bulb Research Program Research Newsletter:
It is important to start clean! A thorough cleaning of all bulb handling, planting and cooling facilities will help to avoid problems in forcing, especially with diseases such as Trichoderma. When tulips are thickly rooted in pots, the lack of soil among the roots makes the roots more susceptible to drying out, salt accumulation or any number of other stresses, and weakened roots are thought to be more susceptible to the Trichoderma pathogen.
Read the whole article. Starts on page 3.