60 STATE POMOLOGICAL SOCIETY. 



Beauty has almost been superseded by less valuable sorts in many 

 localities. 



Unfortunately there has been no opportunity for personal inves- 

 tigation of this disease at our experiment station, since there are 

 no bearing trees available. However, from the marked success 

 attending the work of other experimenters I am convinced that the 

 treatment suggested for apple scab will be satisfactory in this case 

 as well. Professor Beach of the experiment station at Geneva, N. 

 Y., as a result of some work conducted on a commercial scale, 

 found that while the average cost of spraying each tree five times 

 during the season was about forty-eight cents, the increase in the 

 commercial value of the fruit actually sold was about $5. In other 

 words, while the average receipts from the Seckel trees which were 

 sprayed were $5.70 per tree, the average receipts from the 

 unsprayed trees were but ninety-three cents. White Doyenne gave 

 even better results. 



3. Black-Knot. 



To every plum grower in the land the very name "black-knot" 

 suggests an eternal struggle with the powers of darkness, and it is 

 unnecessary to speak of the outward appearance of the disease. 



Many have supposed the "knots" or wart-like excrescences to 

 be caused by insects, for frequently on cutting open one of the 

 warts larvffi will be found inside. But in the first place insects are 

 not always present — never in the early stages of growth ; and in 

 the second place no gall producing insects have ever been found. 

 There can no longer be any doubt that the trouble is due to a para- 

 sitic fungus — Plowrightia morbosa. 



Without entering into details, we may briefly trace the life his- 

 tory of the fungus. It is generally conceded that the knots first 

 make their appearance in the fall, when they may be seen as slight 

 swellings of the bark along the branches. But little growth is made 

 till the following spring when the increase in size is very rapid. 

 This rapid growth is specially noticeable about the first to the mid- 

 dle of June when the bark which at first covers the diseased tissue 

 is burst open and the knot presents a dark green velvety surface 

 due to the immense number of spore-bearing stalks (conidia) which 

 are produced at this time. 



Later in the season the surface of the knot becomes rough and 

 covered with little pimples which are the receptacles of another kind 



