212 The Commercial Apple Industry 



aphis (Aphis sorbi) because of its pinkish to purplish color. 

 This louse is a more serious pest than the others since it 

 not only attacks the foliage, but also causes severe damage 

 to the young apples. (See Plate XV.) These injured 

 fruits, known sometimes as " aphis apples," are frequently 

 much dwarfed and distorted in shape and have no com- 

 mercial value. The fourth species is the woolly aphis 

 (Schizoneura lanigera), easily recognized by its whitish, 

 cotton-like appearance, particularly when in colonies. 

 This species feeds chiefly on the twigs, axils of the leaves, 

 the trunk, especially where the outer bark has been in- 

 jured, and the roots. (See Plate XIV.) 



The life history of plant-lice is somewhat complicated 

 and worthy of brief mention. The oat aphis and rosy 

 aphis migrate to other host plants in the summer, but 

 return in the fall to deposit their eggs on the apple twigs. 

 The green apple aphis breeds on the apple during the 

 entire season as does also woolly apple aphis, although the 

 latter has an alternate host plant in the elm. 



The control of plant-lice is difficult, but by careful and 

 timely spraying satisfactory results can be obtained. The 

 oat, green and rosy aphids hatch in the spring about the 

 time the green tips of the foliage appear. The lice con- 

 gregate upon these tips and soon commence to feed. 



It is in this short period that the fruit-grower has the 

 best chances of effecting control by thorough spraying with 

 a contact insecticide, as nicotine sulfate (40 per cent) at 

 the rate of 1 to 1066 (% pint to 50 gallons of water to 

 which has been added 2 to 3 pounds of soap). If it is 

 desired to spray for the San Jose scale, it may be done at 

 this time, thus giving the tree the so-called " delayed dor- 

 mant " treatment for the San Jose scale and apple aphids. 



