It is a matter of great importance that all cultivators of fruit unite in making observations on this subject, and that it may be done with some unity of purpose.
1. Let the examiner select trees upon which are seen small water-shoots, that have evidently grown late in the fall. Usually, a tuft of withered leaves will indicate them. Examine also all the new wood which retains terminal leaves or is winter-killed at the tips.
2. The pith will be, in apples, an iron-rust color, and in pears greenish black or pepper color; the inner skin will be discolored, and the wood of a greenish, waxy appearance. On cutting down to the point where these shoots unite with the branch or trunk, the diseased sap will be found to have discolored the whole neighborhood. In many cases which we have examined, half the trunk is affected. We examined a bearing pear-tree, which to the eye has not one sign of unhealthiness, but which, on cutting, is found to be affected throughout, and will, undoubtedly, die in spring.
3. Let a comparison be instituted between trees in different circumstances.
Is there any difference between slow-growing varieties and those which grow rapidly?
Is there any difference between trees in cold, northern aspects, whose sap, in autumn, would not be likely to be excited, and those with southern aspects?
Is there a difference between trees upon a fat clay or rank loam of any kind, and those upon a warm, dry, sandy loam. It is supposed that any causes which produce a coarse, watery, flabby tissue in a tree, predispose it to injury by frost, and thus to the blight; and that the fineness and firmness of texture of trees growing in a sand-loam on a gravelly subsoil give them great power of endurance.
4. Let trees which are found to be in an injured condition be marked and examined again as follows:
(1.) At the breaking up of winter, to see if any change of condition has taken place.
(2.) At the breaking of the bud into leaf.