14 



Not only do these experimental facts point to the inefficiency of 

 Paris green as against the later broods of the codling moth, but 

 it is plain that the result was what we must have expected a 

 priori. As the codling moth of all broods deposits the egg habit- 

 ually on the blossom end of the apple, the poison taking effect 

 only in case it reaches the surface of the apple between tlie calyx 

 lobes, it is evident that there is little probability of effectively 

 j)oisoning the fruit when the apple is full grown and pendent upon 

 its stem. 



DANGER OF APPLICATION. 



Furthermore, 1 wish to emphasize especially the point that 

 spraying after the apples have begun to hang dotonward is un- 

 questionably dangerous, and should not be permitted under any 

 circumstances if the fruit is afterwards to be used. The results 

 oi the chemical analysis reported last year show that even heavy 

 wind and violent rain are not sufficient to remove the poison 

 from the fruit at this season; and remembering that the stem end 

 of the apple presents a large conical pit by which the poison 

 could be received and held, where neither rain nor wind could 

 dislodge it, we have additional reason for this absolute prohibition 

 of the use of any poison dangerous to health, except when the 

 fruit is young. 



COMPARISON OF PARIS GREEN AND OTHER POISONS. 



I made this year some further experiments, intended to test 

 the relative efficacy of Paris green and a solution of arsenic* as 

 applied to the codling moth, spraying two trees with the standard 

 arsenic solution and two others with Paris green. The com- 

 parative results are shown in Table IX., from which it will be 

 seen at a glance that, so far as these experiments are concerned, 

 the advantage remains decidedly with the Paris green. f The 

 damage to apples treated with Paris green appears, in fact, to be only 

 about forty-two per cent, of that following treatment with arsenic, 

 — the ratio being not materially different for picked and fallen 

 fruit. 



It will be remembered that I made a similar comparative experi- 

 ment last year with Paris green and London purple, finding then, 

 also, that the former poison was decidedly the more efficient. As 

 only a single tree was treated with London purple, and as I see 

 no sufficient 7'eason why this substance should not act as efficient!}' 

 as Paris green, I think that this result should not be insisted on. 

 The facts, as made out, are given in Table X. 



•The wliitft aiWnlc, aH analyzed for nie in the UniverHity laboratory, proves lo have been ol 

 (.'XcoUent (luality, contalninK nincty-elpcht per (;ent. of nrsenious add. 



tWcfnrtlKir noticed a dnciilod HCort liinK of the k-aves on the trees which were sprayed 

 arsenic, while those to which the Paris preen was applied were entirely uninjured. 



