New York AGRICULTURAL EXPERIMENT STATION. 703 
seldom causes serious trouble in the orchards, though it is found 
to some extent, especially on certain varieties. It does much 
damage here by defoliating pear seedlings in the nursery. We 
have never seen fruit cracked by the leaf blight in New York » 
State, but in States further south it attacks both the fruit and 
foliage, frequently doing much damage. 
The distinction between pear scab and pear leaf blight should 
be kept clearly in mind, for the method of treatment which may 
' properly be recommended for the leaf blight may not be suffi- 
cient for the disease known as pear scab. 
Cause of pear scab.—Pear scab is caused by a parasitic fungus, 
Fusicladium pyrinum (Lib.), Feckl, which attacks both the leaves 
and the fruit. On the leaves it is usually found on the under 
surface, where it appears in spots as shown in Figure 1, Plate 
VIII, which is reproduced from a photograph. The same figure 
also illustrates the effect of the scab on the fruit and its appear- 
ance on the upper surface of a leaf. 
Before the blossoms open the dark scab spots begin to appear 
on the tender new growth, thus showing, as previously stated, 
that infection takes place soon after the fruit buds open. Whether 
or not the fungus is in an active state of growth before the buds 
open is not at present known. The scab spots at first appear as 
a dark olive green or brown mold, with an almost velvety 
surface, bearing minute little bodies known as spores. The func- 
tion of these spores will be readily understood if we say they are 
the seeds of the fungus, although strictly speaking they are too 
simple in structure to be called seeds. Under favorable condi- 
tions of moisture and temperature they readily germinate, and if 
they happen to be located on the foliage or fruit of the pear they 
soon send out a net-work of branching threads, absorb nourish- 
ment from the skin of the leaf or fruit and rapidly form a new 
scab spot, which in turn produces vast numbers of spores. Fig. 2, 
Plate VIII, reproduced from a photograph of a young fruit, shows 
that early in the season the fruit may be very much spotted by the 
disease. Scattered by the winds, the spores quickly spread the 
disease to other portions of the same tree and to other trees. 
Being very light, they easily float in the air and are quickly dis- 
tributed over wide areas by the winds. Since each scab spot is 
capable of producing great numbers of the spores, it is seen at 
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