February, ’18] FRACKER: CROWN GALL AND APPLE NURSERY STOCK 135 
The fourth nursery usually has so few infected trees that the method 
employed in the others was scarcely available here. In one variety of 
their own production, however, which they had been careless in graft¬ 
ing, between 50 and 60 per cent of the “ seconds ” proved to be infected 
with crown gall but only about 10 per cent of the “ firsts.” 
t 
Summary 
In the first three nurseries discussed, 1,012 apple nursery trees were 
examined for crown gall and hairy root and graded into sizes. They 
indicate that the infected trees, if their sale was permitted, would yield 
17 to 18 per cent less gross return to the nursery than a similar number 
of non-infected trees. This is in spite of the fact that the largest of 
the infected trees were usually as large and apparently as strong as the 
non-infected ones. In taking the figures the separate nurseries and 
varieties were tabulated separately and not a single nursery or variety 
shows as great a proportion of trees of salable size among those with 
crown gall as in those without the disease. 
An interesting point in connection with the inspection at the first 
two nurseries, both of which make a practice of providing their cus¬ 
tomers with two grades of stock, was the great diminution in the 
number of first grade trees when infected and the increased number of 
seconds. In many cases there seemed to be a tendency for the infec¬ 
tion to decrease the vigor of the plant without severely forcing its 
size down below commercial value. 
The correlation between small size and infection might be said to be 
due to a possible greater susceptibility of weak trees. Phytopatholo¬ 
gists, however, state that the reverse is true and only strong actively 
growing tissue will support the disease. In view of the marked delete¬ 
rious effects of crown gall in the irrigated orchards of the west, it seems 
most likely that this reduction in size in Wisconsin nurseries is a direct 
result of infection. 
