This section is from the book "The Gardener's Monthly And Horticulturist V24", by Thomas Meehan. See also: Four-Season Harvest: Organic Vegetables from Your Home Garden All Year Long.
Some time since I received from Frank Erbland Waldo, Florida, a piece of a branch of Le Conte Pear tree, which had been attacked by fungus. As this variety of pear has been supposed to be entirely healthy, and proof against disease, the matter is of more than ordinary interest to pear culturists. I submitted the specimen to J. B. Ellis, Newfield, N. J., one of our best authorities on fungus growths. His reply is so interesting that I have thought it proper to have it published in the Monthly. He says :
" I have just examined the piece of limb of Le Conte pear affected in a peculiar manner by a fungus growth which appears to be quite injurious. The first appearance is of little reddish brown circular disks, about one millimetre in diameter at first, and slightly elevated above the surface of the surrounding bark. The little disks continuing to increase, become concentrically cracked and enlarged to ¼ or ½ an inch in diameter, or by confluence spreading along the surface of the limb for one or more inches, and nearly surrounding it. This diseased growth bears some resemblance to the diseased blotches on black raspberry canes sent me last season by Mr. Williams, of Montclair, New Jersey, but differs in the blotches being of a darker color and concentrically cracked and having a distinct raised border. On this diseased growth are two distinct species of Sphseriaceous fungi, belonging to the genus Sphaerella. The species of this genus are found mostly on fallen leaves and dead vegetable stems. A few, however, attack living plants; although not known to be specially hurtful, must of course cause more or less injury to the living organism.
It may be that this diseased growth on the pear limbs is caused by the mycelium of the fungus which has somehow found a lodgment on or in the living branch, and by its growth and development caused the abnormal scab-like excrescences which may be necessary to the production of the perfect asci gerous fungus. In favor of this view the analogous case of the fungus causing the Black Knot on plum and cherry trees may be cited. The only known remedy for Black Knot is to cut off and burn the affected parts, and that would certainly be a safe method with the diseased pear limbs, for it is not likely that the affected limbs where the natural bark has been in great part broken up and destroyed by this excretionary growth will ever recover even if left on the tree".