102 



If the scale is discovered in any locality before it has spread to any 

 considerable extent, it can usually be eradicated by grubbing out ail 

 trees found to be infested, and by spraying thoroly all others in the 

 vicinity; but if it has had time to spread to a number of trees, its 

 eradication will in many cases be impracticable. Even then, however, 

 it may be controlled by spraying annually with one of the solutions 

 described below. 



Spraying for this scale should be done when the trees are dormant, 

 for solutions strong enough to kill the insect after it has formed its 

 protecting scale will seriously injure the foliage and the tender growth 

 of many trees. Spring treatment is most effective; fall treatment is 

 only slightly less so ; but midwinter spraying should be avoided, and 

 spraying operations suspended whenever the temperature in the shade 

 approaches freezing. When the leaf-buds swell and begin to show 

 plainly the green within, the season is over for spraying and it should 

 generally be stopped. If, however, the infestation is bad, and injury 

 by the scale threatens to be serious, it may be advisable to spray even 

 at the risk of some injury to foliage. 



Summer spraying for the San Jose scale is not practicable so far 

 as destroying the scale that is already on the tree is concerned ; for, 

 owing to the weakness of the spray that must be used, only the very 

 young insects can be killed at best, and since these are appearing con- 

 tinually thruout the season, spraying, to be effective, would have to 

 be repeated every two or three days. Summer spraying, however, with 

 the lime-sulphur is no doubt of much value, since its presence on the 

 bark prevents newly hatched young from setting. 



The Lime-Sulphur Wash 



The "California wash," of lime, sulphur, and salt, and the "Oregon 

 wash," of rime, sulphur, and blue vitrol, were used successfully against 

 the San Jose scale on the Pacific coast for several years before they 

 came into use in the central and eastern states. They had been tried 

 in the Atlantic States, but with so little promise of success that their 

 use was almost abandoned until in 1902 it was demonstrated by Mr. 

 E. S. G. Titus, working under the direction of Dr. Forbes, that the 

 lime-sulphur washes were even more effective than the other washes 

 in general use. Since then, the results obtained by Dr. Forbes have 

 been verified by workers in all the states, and the lime-sulphur wash is 

 now the standard insecticide for the San Jose scale. The formula has 

 undergone some change, however, neither the salt nor the blue vitriol 

 being now used. 



