New York Agricultukal Experiment Station. 299 



From the data in these tables it appears: (1) That it is unsafe 

 to leave peach trees exposed to the action of the gas for periods 

 of 12 hours no matter what weight of potassium cyanide per 

 cubic foot is used; (2) that all vigorous trees, even those as 

 tender as peach can be safely treated with as much as 2^ ozs. of 

 98 per ct. potassium cyanide per 100 cu. ft, (.75 grm. per cu. ft.) 

 for a period not exceeding 30 minutes, providing the treatment 

 is given while the trees are dormant; (3) that peach trees which 

 have their vitality reduced by attacks of the scale are liable 

 to be injured after April 1st by use of 2^ ozs. of potassium cyan- 

 ide per 100 cu. ft.; but the injury is not usually such that the 

 trees do not recover and make a better growth than while 

 infested; (4) that peach can be treated in the orchard for inter- 

 vals varying from 30 to 60 minutes with as much as If. ozs. 

 potassium cyanide per 100 cu. ft. (.50 grms. per cu. ft.), .even after 

 fruit buds shov»^ coLor; (5) that Vv'alnut and chestnut will stand 

 the same treatment as peach. 



The tests made in 1900, under tents and hence liable to error, 

 indicate that plums and cherries are similar to peach in resist- 

 ance, and that pears cannot stand If ozs. of potassium C3'anide 

 after the flower buds are exposed. At this time the injury was 

 confined principally to the flower buds, but even where these 

 were injured the entire setting of fruit was not destroyed. 



Johnson has reported injury to peach in Maryland by use of 

 about one-half the above amounts of potassium cyanide per cubic 

 foot. It will be shown under rules for estimating contents of 

 tents and fumigators that, through an error, Johnson has actu- 

 ally used much more than the amount he recommends as safe. 



Caution. — It should be remembered that the larger amounts 

 tested apply only to trees in orchards where the gas comes in 

 contact with the ground. 



EFFECT OF THE GAS ON THE SCALE-INSECT. 



The effect of the gas upon the insects is not as easy to deter- 

 mine as its effect on the trees. Frequently on branches thor- 

 oughly encrusted with this pest not over one per ct. of the 



