CYPRESS BARK SCALE. 19 



be considered as of any importance, because of its great scarcity. In 

 all the writer's observations but three scale insects have been found 

 with punctures in them, from which parasites have escaped. Two of 

 them were from Monterey cypress and one from incense cedar in 

 the Sierra Nevadas. The scarcity of this scale insect in the Sierras 

 would indicate that a parasite was quite active upon it. If such is 

 the case, it has not as yet been noted. 



CONTROL EXPERIMENTS. 



A series of experiments was undertaken in order to find one or 

 more materials capable of reducing the numbers of this very harm- 

 ful pest. Only those sprays were experimented with which would 

 be able to penetrate well into the crevices of the bark, where many of 

 the scales were located. Oil sprays are the only ones which meet 

 these requirements, consequently no others were tried. The oil sprays 

 are capable of penetrating and creeping into all the tiny cracks and 

 crevices of the bark when properly applied. The higher the gravity 

 of oil used, the better is the penetration. 



First, crude-oil emulsion was used, but, being a low-gravity oil, it 

 was unsatisfactory. Next, distillate emulsion was used and, being of 

 somewhat higher gravity, was more satisfactory, but still did not 

 kill more than 10 per cent of the scale insects. Miscible oil No. 1 

 was next used, being of about 28° Baume gravity. This used in a 

 12J per cent solution was quite satisfactory, destroying from 75 to 

 90 per cent of the scale insects. A well-known washing powder was 

 tried as an emulsifler with both the emulsion and the miscible oil, 

 but proved of no value, so its use was discontinued. 



Carbolic sheep dip was tried out^ as this was reported to have very 

 good penetrating powers. This, however, gave only about 30 per cent 

 efficiency and was not used further. Six per cent was the highest 

 used with this, as a higher percentage was believed to be dangerous 

 to the tree. It also made the lungs of the experimenter quite sore. 



Next, miscible oil No. 2 was experimented with, for this had the 

 very high gravity of 33° Baume. A 12 J per cent solution of this 

 proved quite satisfactory, killing a high percentage of the scales and 

 upon second application destroying virtually 100 per cent. Further 

 experiments with this substantiated these results. 



In Table II are recorded all spraying experiments performed 

 upon the cypress bark scale. All spraying was done in the warm 

 part of the day, generally in the afternoon, when the trees were dry. 

 The spray was applied very heavily and thoroughly, every part 

 sprayed being completely drenched. In experiments Nos. 19, 20, 

 and 21 (small trees) the entire tree was sprayed; in all others only 

 the trunk, lower limbs, and foliage were sprayed, as the trees were 

 too large to be treated with a hand pump. The cypress foliage 



