Appendix. 151 



wash in the East is attributed to the frequent occurrence of rains shortly 

 after the insecticide had been applied, and chemical testimony is brought 

 forward in support of this supposition. 



USE OF CALIFORNIA AXD OHEGOX WASHES IS ILLINOIS. 



In the fall of 1901, when an appropriation of $15,000 for insecticide work 

 on the San Jose scale became available to my office, I was embarrassed 

 by the fact that no effective insecticide previously used by us had been 

 found free from serious liability to injure the more tender fruit trees, or 

 at least their fruiting buds. The peach and the plum were especially 

 liable to serious damage by both the kerosene sprays and the whale-oil- 

 soap solution, the first being injurious to the tree, and the second very 

 commonly destructive to the fruit buds and, of course, to the crop of the 

 following year. At this time I received from Professor Cordley, of Oregon, 

 the above-mentioned letter, in which he suggested that I should give the 

 lime, sulphur, and salt compound a thorough test in Illinois, and further 

 said that in Oregon, where this mixture is thoroughly effective, the cli- 

 mate is as moist during the winter — when the spray is principally used — 

 as in any part of the East. I had additional testimony to the same effect 

 from a former student and assistant of mine. Mr. Fred McElfresh. who 

 informed me, after a year's experience in entomological work at the Ore- 

 gon Agricultural College, that the weather of Western Oregon is very 

 similar to that of the greater part of Illinois. 



Under these conditions I decided last fall to use the lime, salt, and 

 sulphur mixture, standard in the Pacific states, for all our Illinois insec- 

 ticide work on the peach and plum, preferring to take the risk of a 

 possible inefficiency of the insecticide rather than the much greater one 

 of serious injury to the orchard tree. The season seemed favorable to the 

 treatment and highly encouraging reports came in from the field through- 

 out the entire winter up to early March. At this time, in order to secure 

 more precise and comprehensive information as to the value of the 

 Oregon and California washes, I detailed one of mj' office assistants, Mr. 

 E. S. G. Titus, to carry out a series of experiments with them under 

 various conditions, and sent him to Sumerfield, in St. Clair county, where 

 he remained for three weeks, supervising the treatment of the trees, and 

 making counts of scales and other observations of the results. 



SECONDARY RESULTS OF THE EXPERIMENTS. 



It was the principal object of these experiments to test the effects of 

 rains on the two washes used, but other important results appeared in 

 the outcome besides those immediately aimed at. Counts of dead and 

 living scales on the check trees not treated and on the experimental trees 

 before treatment, showed a surprising percentage of half-grown scales al- 

 ready dead, the ratio of dead young to living scales varying on different 

 trees and on different parts of the same tree from twenty-one per cent 

 to sixty-nine per cent. This fact had already been observed in other lo- 



