1907.} 



The Cottony Maple Scale in Illinois. 



355 



seven to forty days actually intervened between the time of spraying 

 and the time when the test inspections were made. 



It will be sufficient to say, without entering into details, that a 

 critical examination of 13,000 scales taken from 8 trees showed that 

 86 per cent, of them had been killed by a 19 per cent, emulsion ; and 

 an examination of 23,000 scales taken from 1 1 trees which had been 

 treated with a 20 per cent, emulsion showed that 91 per cent, of these 

 had been killed. Seven trees, two of which had been sprayed Janu- 

 ary II and five March 30 with emulsions containing from 19 to 24 

 per cent, of kerosene, were examined June 10, 49,000 scales in all 

 being, counted, with the result to show that in this case, also, 91 

 per cent, of those alive when the treatment was applied had been 

 killed by the emulsion. The trees covered by these observations 

 were soft maples, lindens, and honey-locusts, but as the percentages 

 of benefit do not differ materially for these different species they 

 need not be separately given. The following table summarizes 

 these data. 



Injury to Trees. 



As one of the results of an examination of trees previously 

 sprayed, made by my inspector June ii to 13, he reported so serious a 

 damage to some erf the trees as to cast doubt on the safety of the kero- 

 sene spray. At Graceland Cemetery, for example, some soft maples 

 had received during the winter an experimental treatment with a 25 

 per cent, kerosene emulsion, evidently prepared in the usual way, and 

 all these trees were in a conspicuously poor condition, with foliage 

 thin, pale, and shriveled, while that of unsprayed trees among them 

 was heavy and dark green. Many of the trees in Lincoln Park on 

 which an emulsion containing 19 or 20 per cent, of kerosene had 

 been used, presented the appearance of a similar, although less seri- 

 ous, injury. A few, indeed, were dead, and dead branches were 

 more numerous on others than usual. 



After a study of the report of my own inspector, Mr. E. O. G. 

 Kelly, on the condition of these trees last June, and a full and care- 

 ful report on the same subject made to Superintendent Warder by 

 Mr. R. W. Braucher, in charge of the spraying operation, and an 

 examination of comparative photographs, made under Mr. Branch- 



