Sept. 22 , 1923 
Bacterial Leajspot of Clovers 
473 
leaves and inhibition of development of new vegetative and floral organs. 
Baccarini’s brief account neither names the causal organism nor includes 
a description of it, but the disease manifestly has no relation to the 
American bacterial leafspot. 
In his comprehensive account of the diseases of the clovers in Russia, 
Jaczewski (3) makes no mention of any form of clover bacteriosis in that 
country, but indicates his familiarity with those in Italy by reference to 
the two listed above. Aside from these investigations, bacteriosis of 
clover in Europe appears not to be "recorded, and the only account of its 
occurrence in America is that included in Manns' (5) studies of the 
“streak” disease which is especially prevalent upon the sweet pea. This 
disease, which is attributed to Bacillus lathyri Manns and Taubenhaus, is 
recorded also as occurring on clover and certain other legumes. This 
bacillus is a yellow organism with very different morphological and 
cultural characters from the clover organism under present consideration. 
Furthermore, Manns’ disease is characterized by longitudinal stem le¬ 
sions, which may later involve the petioles and leaves, thus presenting 
symptoms very different from those of the bacterial leafspot described 
by the writers. 
It is entirely probable that bacterial leafspot has been confused with 
the several fungous leafspots which, especially in their later stages, may be 
difficult to differentiate without the aid of a microscope. At any rate, 
it has not hitherto been clearly recognized and there are no unquestionable 
previous records of its occurrence. 
APPEARANCE OF THE DISEASE 
SEASONAL DEVELOPMENT 
A week or two after the first clover leaves become green in spring bac¬ 
terial leafspot begins to appear. In Wisconsin the infections have 
usually been noted in late May and early June upon the young leaflets. 
Even though clovers remain green throughout the winter in North Caro¬ 
lina, no evidence of bacterial leafspot has been found until the warm 
days of May. In the vicinity of Washington, D. C., infections have not 
been observed until late in May. If the weather continues moist, the 
disease progresses upward with the growth of the plant so that at blossom¬ 
ing time even the uppermost leaves may be conspicuously spotted 
(PI. 1). 
There is no evidence that the disease is systemic, and new infections 
may appear at any time when temperature and moisture conditions are 
favorable. In some seasons severe infection appears on the young 
growth following the cutting, of the first crop and may be found com¬ 
monly in the fields as late as September and October. In 1916 the dis¬ 
ease was very abundant on both the first and second crops of clover at 
Madison, while in 1919 hot, dry weather checked the disease in early 
June, and scarcely any new infections appeared after that time. At 
Arlington, Va., the disease has appeared in three successive years on the 
second crops of clover. 
SYMPTOMS 
As the name implies, the most conspicuous lesions of this disease 
appear on the foliage, although stems, leaf petioles, stipules, and flower 
pedicels are also seriously involved. The presence of tiny translucent 
