In this experiment, "Mike" sulfur appears outstanding in its ability to control 
disease. However, the results of this experiment are parallel with the early results 
obtained in other previously reported experiments, in which combinations of pruning and 
spraying, as well as pruning alone, proved over a period of years to be the more effec= 
tive treatments. Continuation of this experiment is necessary for a better evaluation 
of the effectiveness of this sulfur. 
EFFECT OF TREATMENT ON TREE GROWTH 
Two kinds of data have been kept which throw light on the effect of sprays on tree 
growth as a consideration separate from disease control. Measurements of tree diameters, 
made in connection with two of the spray experiments, give definite evidence that treated 
trees have grown better than untreated trees. Less definite, but perhaps equally in- 
dicative of the value of treatment, is the record of the number of trees selected and 
sold from one of the experimental plots. 
DIAMETER MEASUREMENTS.--In the fall of 1934 diameter measurements were taken of the 
trees in the plot reported above as having received seven years of summer spraying with 
dry wettable flotation sulfur and commercial Bordeaux (see table 1, plot VII), and in 
the following spring similar measurements were made of trees in the plot reported as 
having received dormant and summer sulfur sprays for four years (see table 4). In’ the 
fall of 1938 diameter measurements were taken again of all of the trees then standing in 
these plots. 
The individual trees measured in 1938 were selected from among those measured in 
1954 and 1935, arranged in diameter classes differing by one-half inch, and valued ac-— 
cording to wholesale prices of that date, to give their total sale value as of the winter 
of 1934-35. After measurement in 1938, they were again valued at wholesale prices, as of 
the winter of 1938-39, on the basis of one-half inch diameter classes. ‘The increase in 
the sale value of check groups and of treated groups, after four years of growth, was 
determined by subtracting the 1934~35 valuation from the 1938-39 valuation. The results 
of this estimation are given in table 6. 
For all treatments represented by an adequately indicative number of trees, there is 
definite indication that growth occurred more rapidly and that sale values increased more 
quickly in the treated than in the untreated trees. The inerease in valuation averaged 
50 cents per tree as a result of summer spraying with commercial Bordeaux and 37 cents 
per tree with dry wettable flotation sulfur. For pruning alone this increase amouted to 
5 cents per tree, but with dormant and summer sprays combined with pruning this increase 
was respectively 26 cents and 36 cents per tree for the two types of summer sulfur sprays. 
Although small per tree, these increases in value amount to considerable sums, as 
indicated in table 6, when considered as applicable to a thousand salable trees, and 
represent possible additional sale values of from $50 to $370 per thousand over trees 
receiving no treatment. 
NUMBERS OF TREES SOLD.~-During the winters of 1936-37 and 1937-38 the larger and 
better trees were selected by the nursery owner from one of the experimental plots, in 
order to fill purchase orders for trees of specified large diameters and high quality. 
The exact numbers of suitable trees found in the check group and in each of the treated 
groups are shown in table 7. 
The advantage of treatment for disease control as a stimulant to more rapid growth 
is indicated by the fact that from 3 to 9 per cent more trees were selected from groups 
receiving some kind of treatment than from the untreated check group. These figures 
are the more significant, because the diameter specifications on which the selections 
were made were above the average run of the plot. 
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