382 
Journal of Agricultural Research 
Vol. VIII, No. 10 
may be nearly normal, but there are usually many abortive berries (“shot 
grapes ”). Vines badly affected show small yellowish leaves, short joints, 
upright canes, and abnormally numerous laterals (PL 89, A). The 
blossoms on such vines may all drop without setting, or a few normal 
berries may form on some of the bunches. Such vines seldom yield 
more than half a normal crop. Very badly affected vines show the 
same symptoms in an intensified degree, and toward the end of summer 
many of the leaves turn brown in whole or in spots. These vines bear 
nothing, and usually die after a year or two. 
The appearance of a badly affected vine is very distinct, and the symp¬ 
toms are unmistakable. They suggest very strongly a specific disease; 
but no bacterial, fungus, or animal parasite has been found in connection 
with them. 
RELATION TO ENVIRONMENT 
distribution in the vineyard 
The distribution of the diseased vines is of two general types, which 
may be called the “diffusive” and the “intensive.” 
The diffusive type occurs usually in the lightest sandy soils. Here 
every vine in the vineyard may show symptoms. The disease in this 
case is seldom or never severe enough to kill the vines, but may seriously ' 
diminish the crop. It varies with the year and the variety. Some vari¬ 
eties may be almost immune, and in some years very few vines show the 
effects of the disease. 
The intensive type occurs usually in sandy loams. In some cases of 
this type, a few badly diseased vines, even a single one, may be found 
completely surrounded by apparently perfectly healthy vines. Generally 
the diseased vines occur in irregular, ill-defined spots. Most of the badly 
diseased vines are found more or less in groups, but some of them are 
found among the surrounding healthy vines and sometimes a healthy 
vine will be found surrounded by a group of badly diseased. Healthy 
vines are seldom found near the middle of a large group of badly diseased 
vines. 
Plate 92, B, and text figure 1 illustrate the intensive type of distribution. 
Figure 1, A, represents a vineyard where the attack is moderate and which 
is still producing paying crops. There is no evidence that the disease has 
killed any vines, as the number of vacancies (2.1 per cent) is quite normal 
and they occur among healthy and diseased vines with about equal 
frequency. Only 17.9 per cent of the vines are so badly diseased that they 
produce practically no crop; 26.6 per cent are noticeably affected and 
produce, on the average, about one-half of a normal crop. The remain¬ 
der. 53-4 per cent, are apparently healthy. Such a vineyard would 
produce probably about two-thirds of a normal crop. 
Figure 1 ,B, represents a very bad case of the disease. The vacancies 
represent 20.3 per cent of the area, and they are most frequent 'among 
