XXI.—A Study of Apothecial Development in the Leaf-spot Disease of Red Clover

Abstract

The Leaf-spot Disease of Red Clover, which, as the name implies, confines its attacks to the leaves, is caused by the fungus Pseudopeziza Trifolii (Biv-Bern.), Fckl., (1), (7). It is responsible for the appearance, in early stages of disease, of small purplish spots, which later become brownish-yellow or black in colour. These spots ultimately bear the fruiting discs or apothecia which are found abundantly on both living and dead leaves. The disease was very prevalent, and caused considerable damage to the hay crops at the Welsh Plant Breeding Station, Aberystwyth, in 1923 and 1925. Williams (11), in his extensive studies of the clover plants at this Station, observed that in these years certain varieties were much more susceptible to the disease than others. He states that in the majority of the early varieties, which were more seriously damaged than the later, most of the lower cauline leaves were completely killed off and were shed before the crops were cut. He adds that there does not appear to bo any marked difference between the various late varieties as regards their susceptibility to this disease. The writer, from his own observations of these crops in the field, was struck by the marked frequency with which the apothecial discs occurred in clusters of from three to five in number, and accompanied, though not so frequently, by a similar cluster on the opposite side of the leaf.