CERTAIN ELEMENTS IN NURSERY PRACTICE 199 



fungus Coccomyces hiemalis, and a similar fungus causes the 

 yellow-leaf or shot-hole of plum. The fungus produces masses 

 of spores that appear as small, white, velvety pustules on the 

 undersides of the leaves, opposite the discolored spots. These 

 spores are produced throughout the summer and being carried 

 by wind and rain to other leaves cause new infections. The 

 fungus lives over winter in the fallen leaves on the ground, and 

 in the spring special fruiting bodies (ascocarps) develop in 

 these old leaves. Spores discharged from the ascocarps pro- 

 duce the first infections that appear on the new foliage. 



Control. Lime-sulfur solution 1 to 50, or a dust mixture 

 of 95 parts finely ground sulfur to 5 parts powdered lead arse- 

 nate, is effective for the control of the yellow-leaf disease. 

 The first application should be made when the first-year buds 

 are about six to ten inches high. As a rule, five to seven 

 applications at intervals of about two weeks are sufficient. 

 An attempt should be made to keep as much as possible of the 

 foliage protected throughout the summer. It is usually not 

 necessary to treat myrobalan plum seedlings or the Japanese 

 varieties of plums since the yellow-leaf disease seldom causes 

 much damage on these trees. 



POWDERY-MILDEW OF CHERRY. The mildew of cherry can 

 be recognized by the characteristic upward rolling of the foliage, 

 accompanied by a shortening and an increased thickness of 

 the iriternodes of the twigs. The curled leaves are covered 

 on the under surface with a tangle of white felt-like threads. 

 Usually after midsummer, small black specks may be observed 

 scattered over the surface of the felt-like mass on the underside 

 of the leaf. The disease is the work of the fungus Podosphcera 

 oxyacanthoe . 



Control. The treatments for the yellow-leaf disease of 

 cherry and plum are also sufficient for the control of the 

 mildew. 



