NEW YORK EXPERIMENT STATION BULLETINS. 395 



BLACK KNOT OF PLUM AND CHEERY. 



Ploicrightia Morbosa, (Sclm.) Sacc. 



"Black-knot" is a disease of plums and cherries which causes the forma- 

 tion of a hard, rough, black wart-like surface on an enlarged or distorted 

 outgrowth of the bark. It is not a new disease. Its pernicious charac- 

 ter has long been known. Nearly five years ago Mr. A. J. Downing said 

 of it that " in some parts of the country it is a most troublesome disease 

 and has even destroyed the whole race of plum trees in neighborhoods 

 where it has been suffered to take its course." Could he have looked into 

 the future and seen the plum industry literally wiped out of existence by 

 black-knot not only " in whole neighborhoods " but in whole counties 

 along the famous Hudson river valley, doubtless the strong words quoted 

 above would have seemed to him a faint statement of the destructive 

 character of this disease. Although Downing did not know the real cause 

 of the trouble yet he urged upon his readers the proper remedy, namely, 

 the destruction of all affected parts by fire; but he advocated burning as 

 early as possible in the spring, while, as will be shown hereafter, the proper 

 time is just after the leaves fall. He also gave the following sound 

 advice: " It will be necessary to prevail on your neighbors, if they are 

 near ones, to enter into this plan, or your labors will be of little value." 

 Had his advice been followed and the work of burning all black-knot 

 wherever found been systematically undertaken at that time and enforced 

 by wise laws supported by strong public sentiment in their favor, there is 

 little reason to doubt that in the favored localities along the Hudson river 

 commercial plum orchards might have been paying good profits for the 

 last twenty years instead of presenting as they do discouraging pictures 

 of loss and decay. 



A reliable nurseryman recently made the statement that " Twenty 

 years ago there were shipped from Geneva to the Hudson river country 

 from twenty thousand to twenty-five thousand plum trees annually, where 

 now few or none are sent and the reason for this loss to the nursery trade 

 is fully accounted for by the fact that the black-knot has become so 

 destructive that no one dares to invest his money in plum-growing in that 

 section." 



The following brief accounts of destruction of plum trees by the black- 

 knot are sufficient in themselves to show that this disease must be placed 

 on the list of serious public pests and like the glanders or pleuro-pneu- 

 monia is a fit subject for special legislation designed for its eradication or 

 control. 



Mr. Geo. T. Powell of Ghent, Columbia county, New York, who is 

 director of the department of farmers' institutes of the New York State 

 Agricultural society, writes as follows: 



" The black-knot has swept the plum-growing interest nearly out of 

 existence in the Hudson river valley. When the orchards were being cut 

 down and planting had ceased I put out an orchard of one thousand trees 



