New York AGRICULTURAL EXPERIMENT STATION. io 
saprophytic Phyllosticta as that found on the spray-injury spots 
and by no other fungus which could have caused the spots’. 
What was the real cause of the spots we are not prepared to say, 
but it is very improbable that they were due to any fungus. And 
yet they were typical examples of the apple leaf spot, except for 
the absence of the species of Phyllosticta, to which the disease is 
commonly ascribed. 
If we proceed on the assumption that the apple Phyllostictas 
are not parasites, we must account for the origin of the spots in 
those cases in which they occur on unsprayed trees, as they un- 
questionably often do occur. This is one of the problems yet to 
be solved. <A possible explanation which suggests itself is that 
when a shower is followed by bright sunshine drops of water on 
the leaves act as lenses and concentrate the sun’s rays to such an 
extent as to overheat the tissues underneath. At any rate, it is 
entirely possible that the spots are in some way the result of at- 
mospheric influences. Duggar® has cited an instance in which 
sunshine following rain caused the shot-hole effect in peach leaves. 
So far as known to the writers, the parasitism of the apple 
Phyllostictas has not been previously questioned. In the past 
the presence of Phyllosticta-pycnidia on circular, dead brown 
Spots on apple leaves has been considered conclusive evidence 
that the spots were caused by the Phyllosticta, and the disease has 
been promptly diagnosed as leaf spot. In the future the problem 
of determining the cause of such spots on apple leaves will be a 
more difficult one. It is our opinion that at least a large part of 
the so-called apple leaf spot is due to spray injury and weather 
conditions and is not of fungous origin. 
Returning, now, to the situation in western New York, it may 
be said that the prediction that the sprayed orchards would have 
the advantage at the close of the season, in spite of the injury 
done to the foliage, became a fact. When it came time to gather 
and market the fruit it was found that there was an unusually 
large amount of scab. In many unsprayed orchards the 
entire crop was so scabby as to be almost worthless. Even 
cece tn pee niimeret eainll, Keown IeGkAat kaste ike those associated 
with the spray-injury spots. See foot-note on page 71. 
8Duggar, B. M. Proc. of the Soc. for the Promotion of Agr. Sci. 19:69. 1898. 
