Spring Black Stem is a common fungal, foliar disease caused by Ascochyta medicaginicola (syn.

The fungus survives in stubble from previous cuttings and spreads easily by rain splash, running water, and equipment.

Phoma medicaginis overwinters as mycelium in old stems and fallen leaves, where small pimple-like structures form, called pycnidia, the asexual fruiting body.

[4] Spores germinate about 24 hours after their deposition on susceptible alfalfa leaves if the proper environmental cues are present, a cool, wet environment.

Infection of new shoots occurs as they grow through the residue or stubble of previous alfalfa crops as well.

[5] The fungus invades inter- and intracellular spaces, and chlorosis of the epidermal cells is seen in as little as 3 days after inoculation.

Once it causes necrosis of the epidermal cells, the fungus moves toward the chlorenchyma and cortical tissues.

Root injuries caused by both biotic and abiotic factors, enhance the disease severity.

[6] This is determined as the fungus infects new growth if favorable environmental conditions occur, usually in spring and fall, multiple times during the disease cycle.

It is a widely adapted crop, energy-efficient, and an important source of biological nitrogen fixation.

[13] Spring Black Stem is present in numerous alfalfa fields throughout the Northeast United States.