520 JOURNAL OF ECONOMIC ENTOMOLOGl' [Vol. 4 



per cent of the scale killed. "Very good" means from 90 to 95 per 

 cent of the scale killed. "Good" means from 85 to 90 per cent. "Fair" 

 means from 75 to 85 per cent. "Poor" means from 50 to 75 per cent. 

 "Very poor" means less than 50 per cent. In our experience too much 

 dependence cannot be placed on counts of a thousand scale unless 

 they are drawn carefully from all portions of the tree. Careful obser- 

 vations have shown that the normal mortality of the Gloomy Scale 

 varies from nothing to more than 90 per cent on different parts of the 

 same tree, so that it would be possible for one to count a thousand 

 scale on an untreated tree and estimate that it had done better 

 than a tree which had been carefully sprayed with the best 

 mixture known at the present time. Careful inspections show that 

 the critical points for inspection purposes are the bases of the 

 new growth and protected crotches. However a successful treat- 

 ment always makes itself evident in the appearance and general 

 vigor of the tree, the growth of the new wood and the expan- 

 sion of the bark. The critical inspections, however, were the 

 ones made in late May when practically all of the young of the 

 first brood had settled and become permanently attached to the 

 branches. The pale grayish young were then very conspicuous 

 among the old black scales and their relative abundance at that time 

 indicated very clearly the number of old scale that were still alive. 



From the above tests it seems safe to conclude that any of the 

 soluble oils at 1 to 8 or 1 to 10 are satisfactory remedies for the Gloomy 

 Scale if used while the tree is dormant, one application being sufficient 

 for several years where the scale is slight or moderate. Where the 

 scale is bad two or more applications are advisable. Better results 

 were obtained where the tree was sprayed twice in the same year than 

 where it was sprayed only once. 



None of the commercial Hme sulphur washes were as satisfactory 

 for controlhng the Gloomy Scale as the soluble oils. This we believe 

 is accounted for by the fact that the dorsal scale of this insect is thicker 

 and apphed more closely to the ventral scale than is the case in the 

 San Jose scale. Our observations would lead us to believe that the 

 oils owe their superior killing powers to the fact that they remain 

 moist much longer than the lime-sulphur preparations and are thereby 

 enabled to creep in between the dorsal and ventral scales. The 

 corrosive lime-sulphur washes do not seem to be able to penetrate 

 the thick dorsal scale of this insect. Some of the hme-sulphur washes 

 gave fair results and if spraying for the Gloomy Scale could be repeated 

 year after year, as in the case of the San Jose scale, they might be 

 recommended. But with shade trees this is usually not practicable. 



None of the spring applications were at all satisfactory, and it was 



