It is caused by several species of Fusarium . FHB is favoured by humid conditions during flowering and early stages of kernel development. FHB is recognized in the field by the premature bleaching of infected spikelets and the production of orange, spore-bearing structures called sporodochia at the base of the glumes. During wet weather, there may be whitish, occasionally pinkish, fluffy fungal growth on infected heads in the field.
Diseased spikelets can contain visibly affected kernels.
FDK in wheat are shrunken and typically chalky white, while fusarium mould on barley is an orange or black encrustation of the seed surface. Much of the severely infected wheat is poorly filled and may be blown out the back of the combine due to its low kernel weight. Grain infected after the flowering stage may be heavy enough to be harvested along with healthy grain, although most FDK will result from infections that occur during flowering. The fungus may eventually kill the developing seed at about the soft dough stage. Symptoms of fusarium mould in barley or oats are usually sparse, making it difficult to tell if grain has been infected.