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the effects of spraying when the buds are opening in reducing injuries 

 to the apple crop. In western New York, the hatching of Aphis sorbif 

 Kalt. (rosy apple aphis) occurred during the period of the swelling 

 and breaking of the buds ; all the nymphs probably emerged by 

 24th April, Stem-mothers were observed to be reproducing on 3rd 

 May, and were occupying exposed positions on the stems of the flower- 

 buds or on the underside of the leaves. For a period about 7th May,. 

 a decrease in the numbers of stem-mothers, probably due to enemies, 

 was noted. On 12th May a noticeable increase occurred, coincident 

 with the maturing of the individuals of the second generation. Sohtary 

 stem-mothers or stem-mothers with from 8 to 52 offspring were observed 

 as late as 23rd May at Geneva and 29th May at Wolcott. A few days 

 of high temperature and marked humidity in the middle of June 

 resulted in a rapid multipUcation on the part of the insects, and caused 

 the complete infestation of new leaf-clusters and the tips of young 

 shoots. The stunting and deforming effects on young apples was 

 very evident in the Station orchards by 18th June. Winged forms 

 were first observed at Geneva on 8th June and at Wolcott on 12th June 

 and in the following week were foimd on Plantago lanceolata, L. Large 

 numbers of both winged and wingless forms were present on apple on 

 22nd June. 



Aphis avenae, F. (oat aphis) began to hatch at Geneva on 16th 

 April, and continued until the leaves were showing green. Maturity 

 was reached by some specimens on 26th April and by 3rd May the 

 blossom clusters were heavily infested. Sap was found to be oozing 

 from the feeding pimctures and in some instances the surfaces of the 

 stems were roughened. The leaves were beginning to curl at this date. 

 Winged forms were first detected on 12th May, were abundant on 

 apple by 20th May and by 29th May had practically all migrated to 

 the summer host. 



A. pomi, de G. (green apple aphis) hatched between 16th and 24th 

 April. Stem-mothers began to mature on 4th May, when the blossoms 

 were showing pink. Winged forms appeared on 15th May. At 

 Geneva this species was present in great numbers on the terminal 

 growth of nursery stock and of young trees. The insects showed a 

 tendency to ascend the growing shoots and attack the unfolding buds ; 

 consequently during early summer the damage to the fohage was not 

 very marked, since the insects were not estabhshed on the individual 

 leaves for a prolonged period. During August, the terminal leaves 

 appeared less able to resist attack and frequently became curled, 

 blackened with fungus, or even killed. On 22nd June and on the 

 succeeding days a flight of winged forms was observed, coming from 

 an unknown source and settUng on the imder surfaces of the new leaves 

 of trees in Geneva. 



These three species feed on the succulent tissues, such as stems of the 

 imopened flowers, stems of young fruit, and leaves. Dwarfing of the 

 apples is mainly due to A. sorbi ; the effect of A. pomi and A. avenae 

 on the setting of the crop and the development of the fruit is uncertain. 

 The injuries caused by the three species are cumulative, the damage 

 caused by one species being intensified by the succeeding species. 

 The rate of growth of young apples appeared to be in inverse proportion 

 to the degree of infestation. Malformations were not marked when 

 infestation was restricted to the fohage of a fruit cluster. 



