212 SlIOT-HOLE FUNGUS. [JUNE, 



bursts through the epidermis of both sides of the leaf, in 

 the form of very minute dark-coloured, hair-like tufts or 

 threads which bear the minute spores at their tips. At this 

 stage the diseased patches become dry and brown and drop 

 out, leaving circular holes, suggesting the idea of the leaf 

 having been riddled with small shot; hence the popular name 

 of "shot-hole fungus" (see illustration). 



The reason why the pieces drop out of the leaf is as 

 follows : — The irritation caused by the fungus induces the 

 formation of a circumscribing wall of wound-cork or periderm 

 round the affected area, cutting off its supply of food; the 

 isolated patch therefore dies, contracts and falls out, carrying 

 along with it the fungus, which remains in the fallen patches 

 until the following season, when a crop of spores is produced 

 and infection of the young leaves takes place. When the 

 diseased patches have fallen the remainder of an injured leaf 

 is quite green and appears to be perfectly healthy ; neverthe- 

 less, such injured leaves invariably fall quite early in the 

 season. As a rule when the disease once attacks a tree, 

 owing to the rapid production of spores almost every leaf 

 becomes infected, and it is not unusual for a tree to be 

 completely defoliated early in the season. In such cases the 

 formation of wood is checked, and there is a lack of reserve 

 food which materially affects the succeeding crop of fruit. 

 When nursery stock is attacked to the extent of causing 

 defoliation for two or three seasons in succession, the trees 

 never completely recover. 



Remedies. — Peach foliage suffers most from the "shot- 

 hole" disease in this country. In this case the disease is 

 difficult to check, as, on account of the very tender nature of 

 the leaves, Bordeaux mixture cannot be applied. 



Dr. W. M. Scott, of the U.S. Dept. Agric, has found that 

 a fungicide, known as "self-boiled lime-sulphur mixture," 

 can be used on peach foliage without injury. The propor- 

 tions for a mixture ready for use are : — 8 lb. lime, 8 lb. 

 sulphur, 50 gallons of water. The following is the method 

 of preparation : — 



"The mixture can best be prepared in rather large quan- 

 tities — say 20 pounds, or even 40 pounds, at a time — so as to 

 get enough heat to produce a violent boiling for a few 



