Tapesia yallundae[1] is the causal agent for a variety of cereal and forage grass diseases.

Produces two types of mycelium - one vegetative, yellow-brown, linear, and branching, the other dark and stromalike.

Sclerotia or sclerotialike stromatic mycelium, at first white to yellow-brown but later dark brown, may also be found on the lesions of infected plants.

[2][3] Black apothecia, 0.2 to 0.5 mm of diameter, form at the base of host culms.

[4] Tapesia yallundae can be grown on a moist, sterile wheat and barley straw, oat kernels, and a variety of simple agar media, preferably supplemented with wheat extract.

Young colonies on potato-dextrose agar are gray, compact and mounded.

[2] Polymerase chain reaction (PCR) combined with restriction enzyme digestion of an amplified ribosomal DNA fragment, are now used to characterize T. yallundae isolates.

"First report of eyespot Pseudocercosporella herpotrichoides in wheat in the Prairie Provinces" (PDF).