262 MANUAL OF FRUIT DISEASES 
SHELLING 
Cause somewhat obscure 
Grape-growers in certain parts of America have known this 
trouble for at least fifty years. It has been reported especially 
from Connecticut, central and western New York, and 
Michigan. What appears to be the same disease has been 
observed in Australia (Queensland) and in many parts of 
France. In France there appear to be two forms of shelling : 
‘one in which there is a failure of the flowers to set fruit in some 
or all parts of the cluster, known to the French as coulure ; the 
second form, in which the fruits fall or shell. The latter type 
is the more important in this country ; the losses at times being 
serious. Fifty per cent of the fruit may drop when affected 
with shelling, or rattling. 
Symptoms. 
Affected grapes fall two or three weeks before maturity. 
Those diseased berries, particularly of the green varieties, 
exhibit a peculiar though indistinct mottling of the surface. 
The skin becomes abnormally thick, and the whole berry is 
harder than healthy berries of the same age. The interior of 
such a fruit shows a brown zone just beneath the skin. The 
taste of shelling berries is noticeably insipid as compared to 
the tart, astringent flavor of the healthy, unripe berries. Shel- 
ling grapes separate easily from the stem, leaving the latter 
as if cut with a knife; no such phenomenon occurs with un- 
affected berries. Generally those berries at the lower end or 
at the extremity of the shoulder are first to fall from the bunch. 
Shelling is not always accompanied by foliage discolorations, 
nor is a browning of the leaves a certain indication of the disease. 
Cause. 
The cause of grape-shelling is obscure, although a great 
many suggested causes have been eliminated by close students 
of the trouble. Among the excluded primary causal factors 
