, 
and later with "Mike" sulfur, 127 trees, about 50 per cent, have become diseased; but in 
the group so dusted and also pruned only 87 trees, or 39 per cent, have become diseased. 
Both dusting alone and dusting in combination with pruning appear in this experi- 
ment to have proved less effective than merely pruning out diseased material. This re- 
sult is in accord with results reported previously for the early years of treatment in 
some of the first plots established. Although it may seem that the use of sulfur dusts 
is detrimental rather than useful, there are other considerations, such as the eventual 
disease control obtained over the growth-period of a block of trees and the extra growth 
resulting from the control of leaf spots and a great variety of minor pests. 
FOUR-YEAR RESULTS FROM DORMANT AND SUMMER COPPER SPRAYS 
The relative effectiveness of two copper sprays, applied as dormant and summer 
sprays alone and in combination with pruning, has been tested for four years in two 
experiments involving nearly 1,300 trees. In one of these experiments Z-O was applied 
alone to 143 trees and in combination with pruning to 133 trees, in comparison with 145 
trees receiving pruning only and 136 untreated check trees. In the other experiment in- 
stant Bordeaux was applied to 178 trees and in combination with pruning to 186 trees, in 
comparison with 181 pruned trees and 186 check trees. 
Most of the disease among these trees was the result of Phoma and Coniothyrium in- 
fections. A few cases were caused also by Cytosporina and by Verticilliun,. 
The degree of disease control for the duration of these experiments and the results 
obtained each year are shown in table 3. In both sets of trees treated with Z-O, approx~ 
imately 23 per cent of the trees became diseased during the four years, while about 35 
per cent of the pruned group and 21 per cent of the check group became diseased. There 
were more cases of disease in the treated groups than in the untreated group of trees. 
In the pruned group 75 per cent more trees showed disease than in the untreated group, 
while the sprayed group and the sprayed and pruned group each had 135 per cent more 
trees that showed disease than had the untreated group. 
In the experiment with instant Bordeaux, approximately 335 per cent of the trees 
sprayed with instant Bordeaux became diseased during the four years of the experiment, 
and about 14 per cent of the trees that were sprayed and primed became diseased. In 
the check group about 26 per cent of the trees became diseased, and in the pruned group 
about 25 per cent became diseased. 
These results indicate that the use of instant Bordeaux alone as both a dormant 
and summer spray tends to favor the development of disease, but that this treatment in 
combination with pruning gives a marked degree of control. The degree of control ob- 
tained with the combination of treatments, shown as 46.9 per cent in table 3, is actually 
11 times greater than that given by pruning alone. 
FOUR-YEAR RESULTS FROM DORMANT AND SUMMER SULFUR SPRAYS 
A series of experiments to test the relative effectiveness of dormant and summer 
sulfur sprays has been in progress on approximately 850 trees for four years. Dormant 
applications of lime sulfur were made in the fall and in the spring on all sprayed 
trees and summer applications of two sets of sulfur sprays were made on definite 
groups of trees. The following sulfurs were used as sprays: Koloform, dry wettable 
fiotation sulfur and "Mike" sulfur. 
Koloform was applied alone to 136 trees and in combination with pruning to 141 
trees. Dry wettable flotation sulfur was applied alone to 142 trees in 1935 and 1936 
and was followed with "Mike" sulfur in 1937 and 1938. This same treatment in combina 
tion with pruning was given also to another group of 142 trees. For comparison a group 
of 145 trees were pruned and a group of 136 trees were left untreated, as checks. 
Disease in these groups of trees was caused mainly by a Phoma and by a Coniothyrium; 
however, a few trees were infected with Cytosporina and a few with Verticillium. 
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