ELM I.KAF CTRL AND WOOLLY APPLE APHID. 



237 



infestation from the woolly aphid was rendered impossible. 

 Leaf curl from elm with pupae and alate forms were secured 

 from the south some time before material at the same stage 

 would be available here,' and migration tests were made. 

 The winged forms from the elm were caged over seedling 

 apples, and their progeny, growing along creases where the thin 

 bark is scaling back, in the axils of the leaves and on exposed 

 roots of the apple seedlings, covered by typical flocculent white 

 secretion, are unmistakably the woolly aphid of the apple. 

 (Fig. 448). The colony in the figure just cited was started 

 May 12-13, 'by migrants from elm leaf curl. Their progeny 

 thrived from the first and the photograph was taken May 29, 

 the day on which the first apterous generation on the apple 

 began to give birth to young. 



On part of the seedlings similar 

 tests were unsuccessful, the nymphs 

 dying very soon or in one case 

 after about two weeks tardy 

 growth. This was probably due to 

 aphid resistant seedlings, the ap- 

 ples from which the seeds were 

 planted being from several differ- 

 ent varieties, and as is well known 

 all apples are not alike susceptible 

 to attacks from the woolly aphid. 



HABITS. 



The woolly aphid occurs upon 

 the apple as a bark feeder and is 

 found upon branches, roots, and 

 tender places on the trunk. These 

 insects are covered by a white 

 flocculent waxy secretion given off 

 as fine filaments through pores in 

 the skin and their colonies are thus 

 readily detected by the masses of 

 white "wool" which renders them 

 conspicuous. (Figs. 438 and 448.) 

 On the roots its attacks induce 

 enlargements or galls or swellings, and in the creases of these 



Fig. 438. Bark colonies 

 of Woolly Aphid on apple. 

 (From Alwood.) 



