38 BLIGHT 
the blight is under control, it is not much trouble to keep it out of the af- 
chard, if the trees are examined and treated regularly. We hare seen 
some very profitable crops of pears raised in orchards treated by this 
method, when the neighboring orchards were half-ruined by the bKaht. 
Fire Blight 
Fire blight is the name commonly given to this disease, which has 
several different forms. It is sometimes called twig blight, fruit blight, 
pear blight, sun-scald, canker, body blight, apple blight, root blight, and 
blight canker. 
It is a bacterial disease which attacks mountain ash, pear, apple, 
quince, Juneberry, haws, and other closely-related plants. It has also 
been reported on plum and apricot. The pear suffers more than other 
fruits from the ravages of blight, and spraying will do no good; how- 
ever, the disease can be controlled with profit. 
The pear has always been a great revenue-producer in nearly every 
part of the country, except where there has been serious trouble with the 
blight, and now blight can be controlled by proper methods and carefiisl 
attention, as demonstrated by Dr. Waite. 
All of the different forms of fire blight in apple, pear, etc., are 
caused by a germ, or bacteria, named Bacillus amylovorous. This is ai 
microscopic plant, which, like the fungi, belongs to a very low order. Ifi 
is rod-shaped and so low in the scale of plant life that there is only one' 
cell to each individual. It is approximately 1-2000 of an inch long — this 
means that it is so small that hundreds of them may stick to a claw of 
a bee or any small insect. 
It has a number of long hair or whip-hke processes (flagella), which 
enable it to move about in the sap of the diseased plant. This bacteria 
multiplies by the very simple process of dividing into two parts at the 
middle. In about half an hour these two parts have reached normal size 
and divide again, and so on until thousands have been produced from a 
single individual in a very short time. 
It attacks all parts of the tree and the first infection is in the spring 
usually in blossoms. The bacteria live during the winter in "hold-over" 
cankers on the large branches and limbs, and are carried by flies, wasps, 
and other means during the spring to the blossoms, causing blossomi 
blight. Bees also spread them from blossom to blossom. 
From the blossom they work down, causing spur blight, and later 
there may be an epidemic of "fruit blight," both of which are more or 
less associated with the "twig blight." 
On the trunk, there are usually growing water-sprouts. These water- 
sprouts are infected from the twigs or cankers, and because the water- 
sprouts are of sappy growth, the blight works down them, and thus gains 
entrance to the main trunk or large branches. In this way the disease 
gets a foothold in the older wood. If it were not for the water-sprouts, 
it would be unable to penetrate the thick bark of a branch or trunk, unless 
it were through a pruning scar or an injury caused in cultivation. Follow- 
ing is a more detailed description of the various effects of blight, all of 
which are caused by the same bacteria or germ. 
Blossom Blight. The bacteria spend the winter in some few of t^e 
old blight cankers on the branches or trunk of the tree. They are alive 
along the margins of the canker next to the healthy bark, and during the 
warm, moist spring days they increase so rapidly that they ooze out in 
small sticky white or brown drops, through the small cracks and holes 
in the diseased bark. These drops are composed of innumerable bacteria 
and a sweet sticky substance, and bees, wasps, or flies lighting here get 
the bacteria on their claws. When an insect goes to a blossom for nectar, 
the blossom is infected, but it takes eight or ten days for inoculation; in 
the meantime the petals often drop. 
