take-all

A disease of grasses and cereals caused by the fungus Gaeumannomyces (Ophiobolus) graminis. The pathogen survives in the soil on crop debris and can infect the crop at any stage. The dense mycelium on the roots and stem bases gives them a typical blackened appearance. If the plants survive until ear emergence the ears have little grain and appear bleached and are therefore called 'whiteheads'.