Life History of a Cercospora Leaf Spot Fungus of Cowpea

SUMMARY

This report deals with a fungus, here designated by the new combination Mycosphaerella cruenta, that causes a leaf and stem spot disease of cowpeas.

Lesions on the leaves are usually irregular and reddish brown. Those on the stems have not been observed to bear conidia.

The fungus has three spore forms in its life cycle. Two of these are herein described for the first time.

This disease has previously been attributed to the conidial stage, Cercospora cruenta Sacc., but evidence of the genetic connection between this conidial stage and its newly found spermogonial and perithecial stages is given.

The pathogen has been isolated in pure culture from conidia and from ascospores, both of which gave rise to typical Cercospora conidia.

The pathogenicity of this fungus has been established by inoculation experiments with conidia and with ascospores.