34 
Colorado Experiment Station 
The bark under these blotches becomes dry and brown. In severe 
cases the bark shrivels and the young tips often curve or are killed 
outright. Spots on fruit are at first musty or frost-like patches 
which later become almost pure white (Plate VIII). The skin 
under the spots becomes brown and the flesh becomes hard. The 
entire crop is often ruined for market. 
Control .— (i) Plant trees far enough apart to allow free cir¬ 
culation of air. This tends to prevent development ol mildew. 
(2) Open head system of pruning is to be preferred. 
(3) Spray with lime-sulfur solution, 1-50, with or without 3 
pounds of iron sulfate added to 50 gallons of the mixture. Addi¬ 
tion of iron sulphate increases covering and sticking qualities. 
(4) Dusting with flowers of sulfur is also effective. This can 
be easily done with a dusting machine. The sulfur should be ap¬ 
plied as early in the morning as possible while the dew is still on the 
foliage. 
Applications for lime-sulfur or sulfur treatment : 
(a) First application, made as soon as the disease appears 
and before it has become thoroughly established. 
(b) Later applications, made at intervals of 9 days or often- 
er, according to the severity of the disease. One or two 
applications may be sufficient while in some seasons five 
or six applications are necessary. 
PEAR. 
Fire Blight. —Fire blight of the pear, apple, quince, apricot, 
and plum attacks blossoms, twigs, limbs or body, and fruit. The 
blight attracts special attention two or three weeks after the blos¬ 
soming period. The fruit spurs at first shrivel, turn brown, and 
then black. Blight works down the twigs and branches into the 
trunk or body of the tree, often causing the destruction of the entire 
tree. The affected portion is somewhat sunken, dark in color, usu¬ 
ally with a brownish tinge. In spring the diseased bark may be 
slightly blistered, and here and there drops of a clear, slimy liquid 
may collect. Later in the season, when the progress of the blight 
is checked, the infected bark shrinks, becomes smooth, and forms a 
definite line of division between diseased and healthy tissues. The 
trouble is seldom found on mature fruit. Hold-over canker on 
twigs is shown in Plate X. 
The disease is caused by a bacterium which is spread chiefly 
by insects. 
Control .— (i) Spraying the trees with a fungicide is not ef¬ 
fective. 
(2) A number of blight remedies have been placed on the mar¬ 
ket by manufacturers. They are supposed to make the trees im- 
