the total number of trees upon which it was tested are given, as are also the least 
and greatest degrees of prevention obtained. In determining average effectiveness, 
plot data have been weighted, whenever possible, in terms of the number of trees in 
the tree blocks concerned. In such cases the indexes of average control given in 
the table are considered to be more fairly expressive of the values of the treat- 
ments. 
A casual inspection of table 5 will leave 3 outstanding impressions; 
namely, that more than half of the treatments appear to have no value, that not all 
the treatments that do have value give consistently positive results, and that the 
degree of effectiveness demonstrated by effective treatments often is disappoint- 
ingly low. However, certain treatments negative as to their averages, have positive 
value under some conditions, and a few of the effective treatments have positive 
averages sufficiently high to indicate definite, practical usefulness. 
A visual comparison, based on the averages given in table 5, of the effec~ 
tiveness of tested treatments is shown in figure 1, in which bars reaching to the 
“right represent effective and bars reaching to the left ineffective treatment, the 
length of the bars representing the percentage of control or lack of control. 
By examining this diagram it may be seen that those treatments for which 
ee rootiveness has been demonstrated include (1) pruning, (2) copper sprays supple- 
“mented by pruning, (3) sulphur dusts, and (4) sulphur dusts supplemented by pruning. 
“Those demonstrated to be ineffective include (1) copper sprays, (2) sulphur sprays, 
i (3) sulphur sprays supplemented by pruning. 
I A definite basis appears to have been demonstrated for judging the effec- 
tiveness of any treatment. It will be noted that all the treatments extending on 
the positive side in figure 1 involve either pruning or dusting and that, without 
