. 69 



orcliards, already considerably or badly infested and situated in a 

 generally infested territory, by measures which would make this 

 economically worth while; and at the same time to show which of 

 the various treatments used was the most successful and the most 

 profitable. This purpose was in part defeated, however, by the failure 

 of a company with which our contract for insecticide supplies was 

 made to deliver the materials ordered in time for use in 1910, A 

 breakdown in their factory of which we were not notified until it 

 was too late to obtain supplies from another source, prevented our 

 spraying these orchards in that year, and the San Jose scale conse- 

 quently multiplied for a season without restraint. These orchards 

 were saved notwithstanding, and are now in profital)le use, but at a 

 heavier loss and a greater expense than was necessary. 



Experiments op 1907-08 



Two apple orchards, originally of 1200 and 1600 trees respect- 

 ively, belonging to James M. Etherton and Homer Etherton, and 

 situated about eight miles south of Murphysboro, Jackson county, in 

 southern Illinois, were selected for these tests. Both contained Ben 

 Davis and Winesap apple-trees, so set in the spring of 1903 with 

 two-year-old nursery stock that the orchards could be readily divided 

 into similar experimental plots of sufficiently large size to permit the 

 omission of the marginal rows of the plots and the use, for compara- 

 tive purposes, of the central rows only. This, as will be shown, is 

 an essential point in experiments of this description, since check and 

 experimental plots placed side by side influence each other in a way 

 to diminish the infestation of the margins of the former and to in- 

 crease those of the latter. 



Infestation data were obtained by a critical inspection and grad- 

 ing as described in an earlier article on "Comparative Experiments 

 with Various Insecticides for the San Jose Scale," published in the 

 Twenty-fourth Report of this office, pages 59-77. 



GRADING OF THE TREES 



The trees in the experimental orchards were carefully examined, 

 one by one, November 11 and 12, 1907, by W. P. Flint and L. M. 

 Smith, of the State Entomologist's staff, under the general super- 

 vision of Mr. West. These inspectors worked together until it was 

 evident that their procedure was uniform, after which they worked 

 separately. The trees were graded on a scale of 10 degrees, the sev- 

 eral grades having the following significance: — 



1 signifies a tree infested by a trace of the San Jose scale— so 

 very slightly infested that one must search to discover the insects: 

 2, a tree slightly infested,— that is, having scattered scales upon it, 

 nowhere clustered and yet fairly numerous; 3, a tree slightly in- 



