480 



JOURNAL OF ECONOMIC ENTOMOLOGY 



[Vol. 8 



SO bad, however, While part of the infestation, here as elsewhere, is 

 unquestionably due to faulty application, inefficient methods cannot 

 be blamed for everything. The spraying tests below recorded were 

 carried out thoroughly. The weather was ideal and the insects were 

 drenched with liquid. Nevertheless none of the sulphur sprays 

 afforded anything like satisfactory control and this year even the 

 Orchard Brand of oil failed to give its usual complete success. Un- 

 questionably under conditions like this, sulphur-hme as well as other 

 sulphur sprays should be abandoned in favor of other materials having 

 different insecticidal properties. 



20 days 15 days 15 days 20 days 



Sulphur-Hme, 10° 65% 41% 28% 43% 



Sulphur-lime, 5° 35 41 39 45 



Sulphur-lime, 3° 92 59 45 45 



Sulphur-lime, T 69 63 61 32 



Sulphur-soda, 3° 86 51 67 29 



Sulphur-soda, 2^ 97 72 67 46 



OU, 5% 7 5 3 3 



Check 89 98 94 55 



This investigation has shown that differences in results from spray- 

 ing are due to locality rather than to the strength of the solutions used. 

 There is a much greater variation in the effectiveness of the three 

 degree sulphur-lime comparing Wenatchee and Clarkston than there 

 is when comparing a two-degree with a ten-degree sulphur-lime used 

 at "Clarkston alone. This contrasting difference between Wenatchee 

 and Clarkston cannot wholly be ascribed to climate, nor to the con- 

 dition of the trees, nor to the water used in diluting the sprays, nor to 

 comparative thoroughness of application, nor apparently to any com- 

 bination of extrinsic factors. The prevalence of scale at Clarkston 

 and its scarcity at Wenatchee where effective spraying has kept it in 

 complete control, further bear out the supposition that there is an 

 inherent biological difference in the insects of the two places. 



Vice-President Cooley: Could you find no other cause than 

 heredity for the resistance to treatment? 



Mr. a. L. Melander: That is the only cause that has been de- 

 termined thus far. 



Mr. S. W. Foster: In comparing treatment on different trees, the 

 weather conditions should be similar at the time parallel tests are 

 made. A variation of a week's time in doing part of the spraying 

 might give quite different results. 



Mr. a. L. Melander: In the tests mentioned the weather con- 

 ditions were as near similar as possible. 



