burn them. The insect-blight does
not affect the tree far below the location of the worm. Watch your trees
closely, and cut off all affected parts as soon as they appear, and burn
them immediately, and you will soon destroy all the insects. But very
soon after the appearance of the blight they leave the limb; hence a
little delay will render your efforts useless. These insects often
commit the same depredations on apple and quince-trees. We had an
orchard in Ohio seriously affected by them. We know no remedy but
destruction as above.

_The Frozen-Sap Blight_ is a much more serious difficulty. Its nature
and origin are now pretty well settled. In every tree there are two
currents of sap: one passes up through the outer wood, to be digested by
the leaves; the other passing down in the inner bark, deposites new
wood, to increase the size of the tree. Now, in a late growth of this
kind of wood, the process is rapidly going on, at the approach of cold
weather, and the descending sap is suddenly frozen, in this tender bark
and growing wood. This sudden freezing poisons the sap, and renders the
tree diseased. The blight will show itself, in its worst form, in the
most rapid growing season of early summer, though the disease commenced
with the severe frosts of the previous autumn. Its presence may be known
by a thick, clammy sap, that will exude in winter or spring pruning, and
in the discoloration of the inner bark and peth of the branches. On
limbs badly affected on one side, the bark will turn black and shrivel
up. But its effects in the death of the branches only occur when the
growth of the tree demands the rapid descent of the sap: then the
poisoned sap which was arrested the previous fall, in its downward
passage, is diluted and sent through the tree; and when it is abundant,
the whole tree is poisoned and destroyed in a few days; in others more
slightly affected, it only destroys a limb or a small portion of the
top. Another effect of this fall-freezing of sap and growing wood, is
to rupture the sap-vessels, and thus prevent the inner bark from
performing its functions. This theory is so well established, that an
intelligent observer can predict, in the fall, a blight-season the
following summer. If the summer be cool, and the fall warm and damp,
closed by sudden cold, the blight will be troublesome the next season,
because the plentiful downward flow of sap, and rapid growth of wood,
were arrested by sudden freezing.