PLUM DISEASES 363 
Lodeman, E.G. Black knot of plums and cherries, and methods of treat- 
ment. Cornell Univ. Agr. Exp. Sta. Bul. 81:637-655. 1894. 
Butz, G. C. Black knot on plums. Pennsylvania Agr. Exp. Sta. 
Bul. 13: 3-4. 1890. 
Selby, A. D. Peach yellows, black knot, and San José scale. Black- 
knot. Ohio Agr. Exp. Sta. Bul. 72: 206-209. 1896. 
Lrear-BLIGHT 
Caused by Coccomyces Prunophore Higgins 
Leaf-blight, leaf-spot, shot-hole and yellow-leaf are all names 
referring to the disease under consideration. A very similar 
disease affects the cherry (see page 172). i 
Among plums the European varieties are notably susceptible 
to leaf-blight ; these may be completely defoliated in wet sea- 
sons. On the other hand, Japanese plums and Myrobalan 
seedlings are comparatively resistant, the disease being of little 
consequence thereon. 
Affected leaves show dead spots at first (Fig. 105); but soon 
the dead tissue falls away, leaving a circular hole, whence the 
name shot-hole (Fig. 105). This type of symptom is common 
onthe plum. At times leaves are completely riddled with holes. 
. Sometimes affected leaves turn yellow, whence the name yellow- 
leaf. The similar disease on cherry shows less shot-holing and 
more yellowing of the leaves than in the case of plum. In 
most seasons if sufficient moisture is present, white, velvety 
pustules appear on the lower surface. These are coils of spores 
belonging to the conidial form of the causal fungus Coccomyces 
Prunophore (commonly known as Cylindrosporium Padi). 
Bordeaux mixture 5-5-50 is effective in the control of plum 
leaf-blight, but this fungicide may injure the foliage, particularly 
in nursery-stock. Lime-sulfur, on the contrary, diluted 1-50, 
may be used without fear of such injury. In the orchard, spray 
as follows: (1) ten days after the blossoms fall; (2) three weeks 
after the first application; (3) three to four weeks after the 
