168 Report of State Board of Horticulture. 



to 11, 12, and 13 of Lot 3, we find that in the latter ninety-four per cent 

 of the scales were finally killed, and in the former only eighty-two per 

 cent — an unmistakable indication that the Oregon wash was not at all 

 affected in these experiments by water treatment; while the effect of 

 the California wash was considerably reduced — a clear difference of 

 twelve per cent of effectiveness in favor of the Oregon wash. 



Comparing next the general averages of final effects shown by the 

 ratios for corresponding trees of Lots 2 and 4, contrasting thus with 

 respect to these two lots the advantages of the California and the Oregon 

 wash, we find them to be as eighty-eight per cent and ninety-two per 

 cent respectively — a difference of four per cent in final effect shown by 

 this group of experiments in favor of the Oregon wash. 



Bringing together the two lots representing each insecticide treatment 

 and combining averages for the two insecticides as represented by the 

 four lots of trees, it appears that ninety-two per cent of the scales were 

 destroyed by the Oregon wash on fifteen trees as compared with eighty- 

 seven per cent on fifteen trees identically treated after spraying with the 

 California wash — a difference of five per cent in favor of the former 

 treatment.* 



THE TENT EXPERIMENT. 



All the preceding experiments were intended to test the effect of arti- 

 ficial applications of water on the action of the two insecticides, these 

 applications being made in a way to simulate the effects of rainfall. They 

 were interfered with slightly by the three periods of light rain, the effects 

 of which could not be clearly separated from those of the artificial treat- 

 ment. 



With a view to a test of the effects of rainfall, a small experiment was 

 undertaken in which two trees — one treated with the California wash 

 and the other with the Oregon wash — were covered with heavy canvas 

 during the night and whenever rain threatened by day. Two other trees 

 were similarly treated and left at all times exposed, and still two more, 

 selected because of their close correspondence to the experimental trees 

 were reserved without treatment, as checks. This experiment was begun 

 March 20. The trees selected (the only ones remaining available) were 

 peach trees on high ground and light soil, heavily infested, and in very 

 poor condition. The drouth of the preceding season had affected them 

 very seriously, the young wood being largely killed, and only twenty- 

 nine per cent of the young scales on them being still alive. 



The weather was favorable to the experiment. The insecticides were 

 applied on the afternoon of March 20, and a slow fine rain began at five 

 p. m. of the same day and continued until nine o'clock and for an un- 

 known time into the night. Rain fell in a continuous drizzle, broken by 



*The slight difference between this statement and the one on p. 1.53 is due to the fact 

 that in the former certain trees treated with the California wash were included which 

 were not exactly duplicated as to treatment by any of those treated with the Oregon 

 wash. 



