166 



JOURNAL OF ECONOMIC ENTOMOLOGY 



[Vol. 4 



of these, or 88.7 per cent, were freed from Aphis, leavmg 11.3 per cent 

 infested. Fully 39.3 per cent were knotty, and only 60.7 per cent 

 could be used for grafting. 



The relative value of these three series of experiments can be shown 

 best by the following table: 



SUMMARY OF EXPERIMENTS 



Number < Date of spraying 

 of series 



Per cent of 



infested trees 



freed from 



Aphis 



Per cent of Per cent of 

 trees remain- [ knotty 

 ing infested 1 trees 



Per cent of 

 trees saved 

 for grafting 



1 July 26 



2 Sept. 10 and Oct. 1 



3 Oct. 1 



5 



12.6 

 11.3 



20 

 28 

 39.3 



SO 

 72 

 60.7 



A word should be said at this place about the effect of the kerosene 

 emulsion on the roots. None of the seedlings were killed, and the tops 

 showed no ill effects. On examining the roots, however, it was 

 evident that the late sprajdng had killed a large number of the smaller 

 rootlets and root hairs. These effects were not noticeable on the 

 trees sprayed July 26. 



Observations on two-year-old Nursery Stock 



The two-year-old apple trees in the nurseries which were examined 

 this summer contained from 20 per cent to 25 per cent infested trees, 

 and several means were tried to free them from Aphis, or at least to 

 prevent further spreading. In one of the nurseries containing about 

 thirty thousand trees kerosene emulsion of 15 per cent strength was 

 applied in a spray. Wherever the spraying was done properly it was 

 quite effective, but no definite figures can be given at this time since 

 the detailed examination will be made in the spring. 



At another nursery containing about forty-five thousand trees, the 

 trees had been dust rubbed. When they were taken up in the fall, 

 about 3 per cent were thrown away as worthless becauge of the effects 

 from Aphis. Of the 318 trees examined in this packing house, thirty- 

 eight were found to have some Aphis. Taking this as a basis, 12 

 per cent of the stock taken in was infested. Adding to this the 3 

 per cent thrown away in the field, the infestation in fall has amounted 

 to 15 per cent. 



At a third nursery containing about three hundred thousand trees, 

 the trees were rubbed with kerosene emulsion. About 2 per cent 



