Emory S. Crosby

Publication Date


Advisor(s) - Committee Chair

Luther Baxter, H.L. Stephens

Degree Program

Department of Agriculture

Degree Type

Master of Arts


Plant pathologists have worked to some extent for many years in an attempt to describe the complete physiology of the organism responsible for pepper spot of clover, particularly as found on white clover (Trifolium repens, L.). These works have not been extensive or concentrated and at the present time, no definite conclusions have been reached.

The causal agent of pepper spot of clover is Pseudoples trifolii (Rostr.).

Pseudoples trifolii usually is found parasitizing clover in the early spring and continues throughout the spring until the temperature exceeds thirty degrees centigrade. Elliott established that Pseudoples trifolii will not produce infectious spores when the temperature is above thirty degrees centigrade.

No evaluation has been accurately made to ascertain the exact losses sustained due to this disease; however, it is certain that the injury incited to the leaves of white clover by the pathogen would hinder the food manufacturing capabilities of the individual plants, thus rendering the plant incapable of full potential growth.

Pseudoples trifolii is widespread in North America and England. In North America Pseudoples trifolii attacks both white clover and alfalfa (Nedicago sativa); however, in England the pathogen has only been described on white clover.

Elliot ascertained that the infectious spores were able to remain viable throughout periods of freezing at a temperature of minus ten degrees centigrade, thus finding a method whereby infection could potentially occur in the spring following severe winters.

It is the writer’s intention, in the following work, to critically study and evaluate previous investigations concerning the physiology of spore formation and ejection in Pseudeples trifolii.


Agriculture | Biology | Microbiology