16 



COMPARATIVE MERITS OF THE ARSENICAL SOLUTIONS. 



We are vitally interested in the best methods of fighting the Codling Moth. We 

 expect a big crop of apples next year, and we are investigating the spraying vrith 

 the arsenical solutions. I don't see why, from a chemical standpoint, the reason for 

 using Paris green or London purple, as both are hard to make a perfect solution, and 

 it must be the arsenic which does the good. Why not use the common white arsenic ? 

 It is easily dissolved, and with concentrated lye will make a perfect and stable solu- 

 tion, and is cheap. From all that I can learn from California and the East a weak 

 solution, used frequently, is better than a strong solution, as the stronger solutions 

 burn the foliage. I will try one-half pound arsenic, 1 pound concentrated lye, to 400 

 gallons water, and will spray the latter part of May, June, and July. * * *. — [A. 

 Gosliu, Oregon, Mo., December 26, 1887. Addressed to Prof. S. A. Forbes. 



Eeply. — Your letter of the 26th of December, addressed to Prof. S. A. Forbes, has 

 just been referred by him to this office for reply. White arsenic has been used against 

 the Codling Moth by several experimentors, with a fair measure of success. J. N. 

 Dixon, of Oscaloosa, Iowa, was the first to use it for this purpose, and he was cn- 

 tliusiastically in favor of it. In his essay on orchards and insects published in the 

 Transactions of the Iowa State Horticultural Society for the year 1882, he advises a 

 much stronger solution than the one which you i)ropose to try. Less than 1 pound of 

 arsenic to 150 gallons of water, he states, will burn the foliage, and he himself was 

 accustomed to use 1 pound to 200 gallons of water. He first dissolved the arsenic by 

 boiling in a smaller quantity of water, afterwards diluting to the required strength. 

 The tests of later experimenters give the preference to London purple and Paris green, 

 for the reason that they seem to take less eff'ect ux)on the foliage than the arsenic 

 alone. In other words, when the solution of white arsenic is strong enough to kill 

 the insects in one or two applications it is very likely to burn the foliage. This is not 

 an absolute statement, but a comparative one. Cook, of Michigan, prefers London 

 purple; Forbes, of Illinois, and Wickson and Klee, of California, give the preference 

 to Paris green. I myself am inclined to the opinion that London purple, on the 

 grounds of effectiveness and cheapness, as well as from the fact that trees which have 

 been treated can be readily distinguished by color, is perhaps the best substance 

 which can be used ; although its advantages over Paris green are slight. It should 

 never be used in a solution stronger than 1 pound to 100 gallons, and it should be ap- 

 plied as soon as the blossoms fall. 



If, however, you are still inclined to experiment with the arsenic and concentrated 

 lye, I shall be very glad to learn your results, and such an experiment as you propose 

 will certainly be instructive. — [February 16, 1888.] 



PROBABLY A NEW ENEMY TO PEAR FROM OREGON. 



Inclosed find affected X)oars and leaves, also an insect which I detected eating the 

 foliage of my young pear trees. I saw none on the bearing trees, but as nearly all the 

 fruit is affected on them (three trees left of an old orchard) the iniereuce would be that 

 they had left the fruit to attack the foliage on the young trees just set out. I have 

 just set out an orchard of 150 acres, and want to head ofi" all destructive insects. 

 What is this insect and what the remedy? — [R. S. Wallace, Salem, Oregon, May 12, 

 1888. 



Reply. — 1 have read your letter of May 12, and examined the accompanying speci- 

 mens with considerable interest, for the reason that this insect has never been known 

 before to do such damage as you describe. It has no conmion name, but is a snout- 

 V)eetle, known as Aragnomm (jriHcns. ^lay I in(]uire whether you are absolutely cer- 

 tain that this is the insect which did tlie damage, and whether you are sure that it 

 injured the fruit ? Nothing is known of ils bivcdiug habits, and the only thing that 

 we cau do is to reconnncnd a rciiuuly for the adult insect. To this end I would adviso 

 you tospiay your young trees with a solution of Paris green or Loudon purple in the 

 proportion of 1 ])ounc] of the ])oiHon to 100 gallons of water * * * . — [May 22, 

 1888, 



