The soil fungi Verticillium albo-atrum and V. dahlia enter plants through the roots, causing Verticillium wilt diseases, or in case of tomato, sleeping disease. The fungi are far from choosy. They love horticulture crops (tomato), trees (olive) and flowers (dahlia). Plants wilt and get brown stains. The heat-lover is especially a problem in the South of Europe, but that might change.
In the lab you learn to recognise this tormentor and get an understanding of his brutal methods.