April, '14] MELANDER: SPRAY RESISTANCE 169 



experiment were ideal in each of these cases. The trees were vigorous, 

 the scales abundant, the appUcations thorough and bad weather did 

 not interfere. The figures show the proportion of scales rated as 

 alive at the successive bi-weekly counts. The first experiment repre- 

 sents 5° factory-made sulphur-lime, approximating one pound of 

 sulphur to three gallons. The second, 3° sulphur-lime, or one pound 

 to five gallons, the third 2°, or one pound to seven gallons. Then 

 follow two sulphur-limes prepared just before the application, experi- 

 ment four, 3°, corresponding to the second experiment, and number 

 five, with the same amount of sulphur but with four times the chemical 

 requirement of lime. The sixth test gives a carbolated emulsion, 

 called Spramulsion, prepared on the Pacific Coast. The last two 

 represent oil sprays made with a fish oil emulsifier: Thomsen's Orchard 

 Brand and a fuel oil emulsified during the tests. 



It will be observed that the normal action of the sulphur-lime is 

 continuous, producing complete destruction of the scale in a little 

 more than a month's time. In the Clarkston experiment, however, 

 from 4 to 13 per cent, or more, of the scales were alive six weeks after 

 spraj'ing, at which time they had begun their spring growth and were 

 probabh' but little susceptible to whatever weathered sulphur-lime 

 remained. 



Attention may be called to the similarity of the results obtained with 

 the last two oil sprays at all three places, showing that Clarkston 

 scales have no resistance to these sprays, and to the similarity of the 

 action of sulphur-lime used at North Yakima and Sunnyside, as 

 compared with Clarkston. It is evident from these figures that the 

 San Jose scale at Clarkston manifests a decided resistance to the action 

 of sulphur-lime. 



Although sulphur-lime has come to be regarded quite as a panacea, 

 because of its destructive action on fungi, lichens, insect eggs, scales, 

 etc., yet it is specifically a scalecicle, and particularly is used against 

 the San Jose scale during its hibernating condition. Other scales 

 are less susceptible, the naked Lecaniums not at all, and thick shelled 

 or active insects emerge quite unharmed from a bath of sulphur-lime. 

 Even the San Jose scale shows a variable susceptibility, for during 

 the growing period sulphur-lime has proved to be much less effective. 

 Furthermore, there is a sex-difference, for among the resistant indi- 

 viduals escaping the action of the spray, the majority are males. 

 Sulphur-lime is not a universal poison; it does not assure certain 

 destruction of all insects; and there is thus a chance for an immunity 

 to manifest itself in increasing degree as the insects become acclima- 

 tized. 



The physiological effect of sulphur-lime is believed to be due to 



