48 THE KEPOL'T UF THE iVo. 36 



by spraying at dillereiit dates. This year we were able to recognize the nymphs of 

 the first instar of sorbi, and now that their identities are established we may safely 

 say that most of the nymphs of the three species are out by the time that the 

 leaves of the more advanced bnds are projecting from one-fourth to half an inch. 



Mr. Biggak: Which do you think would be more effective, concentrated or 

 soluble sulphur? 



Peof. Paerott : I am unable to advise you as to the wisdom of combining 

 nicotinq sulphate with soluble sulphur. You doubtless know that soluble sulphur 

 depends for its insecticidal and fungicidal properties upon polysulphides and 

 sulphides of sodium while lime-sulphur depends on sulphides of calcium. In Xew 

 York we do not recommend a combination of arsenate of lead and soluble sulphur 

 because soluble arsenic is formed. Soluble sulphur can be supplied by itself for 

 the control of San Jose Scale or Leaf Blister Mite or for the control ol Leaf Curl. 

 We take a great deal of pains in our recommendations that fruit growers and 

 farmers should clearly understand tliat they should not use sodium sulphide in 

 combination with either arsenate of lead or other arsenicals. 



Prof. Caesar : I have used calcium arsenate in combination with soluble 

 sulphur and burned half the leaves off the tree>. Is it not possible that your 

 excellent results with the strong lime-sulphur (1 gallon to 8) and black leaf 40 

 on the aphids was due partly to the action of lime-sulphur on the eggs that were 

 almost hatching? 



Prof. Parrott: Yes, that is possible for a small percentage of the eggs; and 

 has already been suggested by the manufacturers oi nicotine sulphate. However, 

 now that we are ablexto recognize the nymphs of the first instar, both Mr. Lathrop 

 and myself were able this year, by observation, as by experimental operations, to 

 show that as far as Eome apples were concerned, ,<-orbi had all hatched by the time 

 we began spraying. Now' had you asked me in 1915, as I have previously stated, 

 I could not have spoken so definitely on this pohit because we did not know the 

 nymphs in their first instar. 



Mr. Eoss : This spring we obtained excellent results in the control of A. 

 malifolice, A. pomi, and A. avenoe in a twelve acre orchard near Vineland, but 

 later on our work was somewhat spoiled by pomi migrants which flew from 

 neighbouring apple trees into the orchard and reinfested the trees. 



Prof. Parrott: I may say in addition, that some of our associates in- New 

 York who have been somewhat reluctant to agree with us in some of our statements 

 relative to sorhi are beginning to change their minds. After seeing the sprayed 

 plants one could hardly draw conclusions very different from those I have presented. 

 The problem for experimental workers now is to ascertain if it is profitable for the 

 average ^grower to spray each spring in order to avoid losses by the rosy aphis. 



Dr. Dearness: I should like to ask Mr. Eoss whether that migration season 

 .seems to hold in the case of the Eosy Aphis. Did I understand jjou right that the 

 generation that comes from the Plantago is oviparous, that there is a migration 

 of viviparas to the Plantago, and then that there is a generation of oviparous 

 from that and whether that seems to be necessary ? 



Mr. Eoss: The alatre which migrate from the apple to the plantain are 

 viviparous, and their progeny are viviparous. The return migrants from Plan'iago 

 to apple are likewise viviparous, but their progeny— the sexual females — are 

 oviparous. 



Dr. Dearness: You think that the migration to the Plantain is necessary to 

 that species? 



Mr. Eoss : I am not quite sure about that. We have been able to make sorbi 



