J^i^toirjology 



A FEW ENEMIES OF THE PLUM. 



PROF. OTTO LUGGER, ST. ANTHONY PARK. 



DISEASES. 



I suppose all persons hold the opinion that a ripe plum is a fine 

 thing to possess, either to eat or to sell. When we consider that of 

 all fruits the plum is the most promising one for this state, we can 

 only regret that our success depends upon so many factors, and 

 that it can not be attained without very much labor and patience. 

 Yet I have no doubt that plums of superior quality and in large 

 quantities can and will be raised in the future. To be successful in 

 this work it is verj^ important to know exactly what obstacles are to 

 be overcome. Studying the question simply from the standpoint of 

 an entomologist and botanist, such obstacles are chiefly parasitic 

 plants and injurious insects; but as there are a large number of 

 both diseases and enemies, I will only discuss a few of the more 

 important ones. 



The Black Knot of the Plum and Cherry. (Fig. l.) 

 Plowrightia niorhosa (Scher./ Sacc.j 



Fig. 1. Black Kxot of the Flux and Cherry.— a, old knot ; h, new swell- 

 ing; c, summer-spores upon knot; d, cavity in old knot filled with threads and 

 club-shaped bodies; e, formation of winter-spores; /, germinating winter-spores; 

 a, b, nat. size; c, d. e, /, greatly enlarged. 



