This section is from the book "The Gardener's Monthly And Horticulturist V20", by Thomas Meehan. See also: Four-Season Harvest: Organic Vegetables from Your Home Garden All Year Long.
I see in the Feb. Monthly, page 52, your Notes on the cracking of the Pear; you claim it is clear to all who have given close observation to the subject, that there are several, if not many causes; as much as to say we are all grop~ ing in the dark. I have never as yet learned of a remedy from our men of superior wisdom; but hold they do not see the exact process in which the fungus is conveyed to the fruit. I am fully satisfied from the experiments I have made, the disease can be exterminated. In order to test my theory, an isolated specimen should be selected which is bearing cracked fruit, all the last summer's growth or wood taken off except a few blossom buds. I hold the fungus after being established on a tree, is perpetuated on that tree, by its propagation on the young wood and fruit; there is no doubt a difference in the susceptability of fruits, in taking on this condition; but close observation will disclose the fact, that the young wood of all varieties of Pear trees do not present the same appearance. Some contain an unbroken cist wherein the fungus lies; in others the cist has opened the fall before, and become harmless.
I will give you an extract of a letter to F. W., Feb. 18, 1874: Dear Sir: - "I find the wood on the Lawrence Pear least infected by fungus; Duchess, Bartlett, Belle Lucrative, very slightly; Beurre Diel, Flemish Beauty, and White Doyenne most. The above observations are pointed. To one year old wood, it should appear a thick skinned pear may resist the injury done in a measure; think the living principle of fungi on some varieties remains enclosed in the cist during the winter, and and does not open until spring when new growth commences, while in other varieties the cist opens the latter part of the same season of fungus propagation, and thereby becomes harm less. It would be well to look for the living spore or seed and ascertain the point".