452 BULLETIN OF THE BUSSEY INSTITUTION. 
PREVENTION OF THE DisEAsE.— From the knowledge that the | 
knot is a contagious disease, caused by a fungus whose ascospores are 
ripened in midwinter, and whuse mycelium does not extend for more 
than a few inches below the knots, and bearing in mind that the 
fungus is indigenous on certain of our native species of Prunus, the 
remedy is obvious. When a knot makes its appearance, the branch 
should be cut off a short distance below the slight swelling of the stem, 
which is found just below the knot. When cut off, the branches should 
be burnt, to prevent the spores from spreading the disease; for, 
although the asci may have but begun to form when the branch is 
cut off, they will grow and ripen their spores even when separated 
from the trees, as we know from experience.* The question arises 
as to the best time for cutting off the diseased branches. We should 
say, cut them off whenever one sees them. ‘The most favorable time is 
late in the autumn, before the ascospores are ripe. But it must not 
be forgotten that the conidia ripen in early summer; and, if knots are 
seen iu the spring, they should be cut off-at once. 
Not only should diseased branches of cultivated cherries and plums 
be removed ; but all means should be taken to destroy the choke cherry, 
the bird cherry, and the wild plum, in the neighborhood of orchards. 
In New Enyland, particularly, the choke cherry can only be regarded 
as a pest. We notice that Mr. Emerson, in the new edition of his 
”? 
“Trees and Shrubs of Massachusetts,” recommends the choke cherry 
as worthy of cultivation on account of its beauty. However opinions 
may differ as to its beauty, there can be only one as to its injurious 
influence on cherry and plum orchards ; and it cannot be too strongly 
impressed upon fruit-growers, that the choke cherry is a most dangerous 
enemy, and should be destroyed. It is quite time that it was generally 
understood, that many of our herbaceous and shrubby plants cause 
or, at any rate, increase disease in our vegetables and fruit-trees. ‘The 
farmer destroys caterpillars wherever and whenever he finds them; why 
should he not also cut down and destroy all trees and shrubs which 
carry a contagious disease into his fruit orchards ? 
* A plum-tree covered with knots was cut down at Newton, Mass., towards 
the end of the summer of 1875, before the ascospores had begun to form; but 
by the first of the following March ripe spores were formed in all the knots, 
notwithstanding the fact that on the first of the previous December the tree 
had been exposed to a temperature of — 8° F. 
