y) 
14 ‘‘ ROUGH-BARK ’’ DISEASE OF YELLOW NEWTOWN APPLE. 
On oxalic-acid agar slants.—After 12 days the surface is covered with 
powderylike growth, white with a tendency toward brown in some 
places. Neither pycnidia nor spores are formed on this medium. 
On sterile apple wood.—Growth white and scant. Pycnidia and 
spores are formed abundantly in 30 days. 
On synthetic agar slants.—After 15 days the medium is covered with 
a luxuriant growth of downlike mycelium, which later becomes dark 
at the surface of the slant. 
On beef bouillon.—Delicate white hyphs permeate the liquid in five 
days. Later the surface is covered with a crust of hyphe having a 
white powdery surface. Pycnidiumlike bodies are produced on this 
crust next to the wall of the tube, but no spores are to be found. 
PREVENTIVE MEASURES. 
While definite spraying experiments for the control of this disease 
have never been carried on, observations in orchards which have 
been well sprayed both in growing and dormant seasons tend to show 
that such orchards may be as subject to the disease as those in, which 
there has been little or no spraying, other conditions being the same. 
One of the orchards showing the disease the worst of any which the 
writer has seen had for several years past been sprayed in the winter 
with a strong solution of lime sulphur for scale, with dilute lime- 
sulphur solution once or twice in the early spring, and has besides 
received three or four applications of Bordeaux mixture during July 
and August. It is possible, of course, that spraying with bluestone 
or strong Bordeaux mixture before the buds open in the spring, with 
subsequent applications of weaker Bordeaux mixture during the 
early part of the growing season, might serve to check the disease, 
but it hardly seems probable. From the fact that fall inoculations 
have not been successful, spraying at that time of the year or in early 
winter for the control of this disease would seem of little value. When 
it is considered that the spores are protected by their pycnidial cover- 
ings under ordinary circumstances, oozing out only under moist con- 
ditions, and that the disease is probably initiated through the germi- 
nation of spores which have lodged in small abrasions, hail marks, 
insect punctures, etc., the probability of successful spraying for its 
control becomes very remote. Spraying, therefore, probably is of 
value only in so far as in helping to maintain the general health of 
the tree it gives an increased resistance to disease. 
From a commercial standpoint, careful pruning, proper cultivation, 
and, when necessary, fertilization seem quite successful as control 
measures, for as long as the trees are in good growing condition the 
disease will not be very serious. 
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