188 



THE CANADIAN HORTICULTURIST. 



orchard. If one wishes choice fruit for i 

 home use, he can Unci nothing better ! 

 than the " Primate," " Early Straw- 

 berry," and " Summer Rose," but save 

 the second named, they are not so 

 desirable for orchard culture. Select- 

 ing early ap})les, and packing them 

 carefully in new half barrels, lined with 

 white paper, or in suitable crates, will 

 greatly increase the market returns for 

 this kind of fruit. — American Ayricul- 

 turist for August, 



THE BLACK KNOT ON PLUM TREES. 



Dr. B. D. Halsted, writes of a seri- 

 ous pest of the orchard, in the Ameri- 

 ca/rt Agriculturist for August. 



Mr. D. D. (;}aines, near Catskill, N. 

 Y., brings us peculiarly distorted 

 branches from his plum orchard, and 

 complains that the trouble is a serious 

 one, as he has over two thousand plum 

 trees more or less affected. The cause 

 of this distortion of the smaller branches 

 is a fungus, and it has long been known 

 as " Black Knot." It has often been 

 claimed by careless observers that the 

 swellings were due to various insects 

 which infest the peculiar outgrowths. 

 The parasitic fungus attacks the young 

 branches in early spring, causing them 

 to increase rapidly in size ; rupture of 

 the bark soon follows, and the soft sub- 

 stance, coming to the surface, expands 

 in an irregular manner, and is shortly 

 covered with a peculiar olive-green 

 coat. The fungus plant is like many 

 others of the same low order of vegeta- 

 tion as the various moulds, mildews, 

 etc., and consists of a multitude of fine 

 threads, that run in all directions 

 through the substance of the plum tree. 

 The olive color of the surface is due to 

 a vast number of minute bodies called 

 spores, which are formed on the tips of 

 the threads, and, breaking away from 



their attachments, serve to propagate 

 the trouble. After the knot has grown 

 to some size, its soft substance oU'ers a 

 good home for various kinds of insects, 

 and it is rare to find such a knot that 

 is not thus infested. This was the 

 strong argument in favour of the view 

 that the knots were of insect origin. 

 The scientific name of the fungus i« 

 Sphceria morhosa, and this, the cause 

 of the black knot, is as much a plant 

 as the plum tree upon which it lives. 



The olive surface-spores continue t-o 

 form through the summer, and at 

 autumn another kind of spore begins 

 to develop within the substance of the 

 knot. These are of slow growth, and 

 are not ripe until the following spring. 

 The only remedy thus far known is the 

 judicious use of the knife. The knots 

 should be cut off and burned whenever 

 they are found. They are most con- 

 spicuous in the winter, when the 

 branches are not covered with leaves ; 

 but when a tree is attacked, it is not 

 wise to delay the removal until a more 

 convenient time. The diseased branches 

 should always be burned, otherwise the 

 spores will continue to form for awhile, 

 and thus propagate the contagious pest. 

 If the tree is badly attacked, it may be 

 best to remove it entirely. 



The Choke Cherry is a favorite host 

 of the black knot, as the neglected 

 fence rows often show in winter. All 

 such trees should be rooted out. The 

 cultivated cherry trees are subject to 

 attacks by the black knot, for which 

 the same remedy as that for th<5 plum 

 tree is recommended. Use the pruning- 

 knife, always at sight, and cut several 

 inches below the swelling, that all the 

 infested portion may be removed. 



Arsenic Water for CoDLiJf Moth. — 

 J. N. Dixon, of Iowa, sprayed his apple 

 orchard with arsenic water to eradicate 

 the canker-worm, and unexpectedly found 

 it a remedy for the codling moth. 



