414 DISEASES OF CULTIVATED PLANTS 



this country. It produces circular or irregular reddish-brown 

 spots an eighth of an inch or more in diameter, often with a 

 slightly raised purplish margin. When old the spots often 

 become greyish. If the infection is bad the spots coalesce 

 and form large brown patches involving half the leaf or more. 

 It usually appears early in the spring, and fresh leaves become 

 infected throughout the season. As a result the leaves fall 

 early in the season, and if this is repeated for several years in 

 succession, the trees become weakened, and the fruit is small 

 and poor in quality. 



Certain other fungi, such as species of Hendersonia, Cory- 

 neum, Pestalozzia, Alternaria, etc., often appear as saprophytes 

 on the diseased patches caused by the Sphaeropsis. 



Perithecia innate, erumpent ; spores oblong, coloured, 

 25 X 10-11 p, borne on sporophores of equal length. 



Scott says that for the control of this disease alone an 

 application of Bordeaux mixture should be made in the spring, 

 a week or ten days after the petals have fallen, a second 

 application four weeks later, and a third about four weeks 

 after the second. Three applications are necessary only in 

 exceedingly wet seasons in sections where the disease is severe. 

 Ordinarily two treatments, one about three weeks after the 

 petals are off and the other four or five weeks later, are 

 sufficient. 



A weak Bordeaux mixture, such as 3 pounds of copper 

 sulphate and 3 pounds of lime to 50 gallons of water, is 

 effective in controlling this disease, Bordeaux mixture of full 

 strength not being required. 



Scott, W. M., U.S. Dept. Agric., Bureau of Plant Industry, 

 Bull No. i2i, pt. 5 (1908). 



CONIOTHYRIUM (CORDA) 



Perithecia membranaceous, or rather rigid, dark coloured ; 

 spores minute, continuous, coloured, borne at the tips of 

 short sporophores. 



Very closely allied to the genus Sphaeropsis, differing mainly 

 in the relatively smaller perithecia and spores, the only 

 tangible difference consists in the sporophores in Sphaeropsis 

 being elongated, whereas in Coniothyrium, the sporophores 

 are very short or obsolete. 



