68 



Annals of Horticulture. 



following table is an interesting and important one, in show- 

 ing the effects of sprays of different strengths as compared 

 with wholesome food : 



Dates. 



No Poison, i lb. to ioogals. i Id. to 200 gals. 1 lb. to 300 gals. 1 lb. to 500 gals 

 —12 Insects. =-12 Insects. — 12 Insects. — 22 Insects. — 22 Insects. 



May 6 . . 





3 



2 





1 



" 7- • 





1 





4 



2 



" 8. . 





1 



2 



2 



1 



" 9. . 





2 



3 



3 



3 



" 10. . 





3 



1 



4 



4 



" 11... 





1 





6 



4 



" 13. • 







4 



2 



5 



" I4-. 





1 





1 



1 



Total, 



t 



12 



12 



22 



21 



"All strengths of the poison mixture here killed the beetles feeding on it, 

 "the difference being seen in the rapidity with which they took effect. In four 

 days from poisoning, the ratios killed were 42 per cent, in lot two, 33 per 

 cent, in lot three, 27 per cent, in lot four and 18 per cent, in lot five." 



The success of the arsenites in combatting curculio on the 

 plum and cherry has led fruit growers to apply them to the 

 peach. This has been particularly true in the " peach belt" 

 of Michigan during the past season. But it was found at 

 once that peach foliage is easily injured by the poison, and 

 this experience has opened again the question of the proper 

 strength of the spray. Cook has published the best experi- 

 ments in this connection. He finds* that "London purple is 

 more injurious to foliage than is Paris green ; and white 

 arsenic — arsenious acid — is more harmful than either. This 

 is doubtless owing to the soluble arsenic which is quite abund - 

 ant in London purple, and almost absent in Paris green." 

 As peach foliage is especially susceptible to injury he recom- 

 mends that only Paris green be applied to it. 



For economic reasons, as well as to avoid injury to foliage, 

 recent tendency is towards weaker mixtures. It is probable 

 that a pound of poison to 250 gallons of water is strong 

 enough for any use, while for the peach and other trees par- 

 ticularly liable to injury, a mixture of half this strength is 

 best. But the spray should always be fine and it should be 

 driven into the tree with great force. There is some evi- 

 dence to show that mixtures of equal strength act differently 



•Bull. 53, Mich. Exp. Sta. 



