applied very promptly as soon as it is evident that it is
likely to be necessary and must cover every part of the tree to be
effective. The object is to prevent the spores from germinating, the
spray being entirely a preventive and in no sense a cure. The disease
most frequently first manifests itself on the tender new growth and on
the blossoms. Two mixtures have been found to control it, namely,
Bordeaux and a weak solution of lime and sulphur. One or other of
these should be applied just before the blossoms open, just before
they fall, and when necessary two and nine weeks later.

(2) NEW YORK APPLE TREE CANKER is usually found mainly on the trunks
of old trees, but it also affects the smaller branches. Practically
every old or uncared for orchard has more or less of this canker, and
where it is not checked it eventually destroys the tree. This fungus
is the cause of most of the dead wood found in old orchards. The
surface of the canker is black and rough and covered with minute black
pimples. It lives over winter and spreads from one branch or tree to
another. As it most frequently enters a branch through wounds made in
pruning, these should be promptly painted over with a heavy lead and
oil paint. All diseased parts should be cut out and removed as soon as
observed. The value of spraying for this disease is not definitely
known, but it is seldom very troublesome in well sprayed and well
cared for orchards.

(3) BLIGHT appears on apple trees in three forms, as blossom blight,
as twig blight, and as blight cankers. It is a bacterial disease
which is distributed by flies, bees, birds, etc., and cannot be
controlled by spraying. The bacteria are carried over the winter in
cankers on the main limbs and bodies of the trees, oozing out in a
sticky mass in the spring. These cankers should be cut out with a
sharp knife cutting well into the healthy bark and then washing the
wound with corrosive sublimate, one part to one thousand of water.
Cutting out and destroying are also the chief remedies to be used when
the blight appears in the twigs and blossoms. It is not usually as
serious on apples as on pears. Some varieties, like Alexander, are
more subject to it than others.

CHAPTER VIII

THE PRINCIPLES AND PRACTICE OF SPRAYING

The spraying of fruit trees in the United States is of comparatively
recent origin, having been a general commercial practice for less than
two decades. It involves the principle of appl