APHIDS 



47 



generation will be winged and migrate 

 to other trees, but the great majority 

 will be wingless and remain to colonize 

 the growing shoots. These develop in 

 from 14 to 20 days and when mature im- 

 mediately deposit young. The lice of the 

 third and subsequent generations during 

 the summer season develop in 10 days. 

 Sometimes winged and sometimes wing- 

 \ ' 



Fig. 2. Winsed Viviparous Female of Green 

 Apple Aphis. Enlarged. 



less forms predominate in the summer 

 generations, most of the former migrating 

 to other trees. These generations are all 

 parthenogenetic, that is, the females give 

 birth to their young without the pres- 

 ence of the male element. The young in 

 this case are born alive, or viviparously. 

 There may be from 10 

 to 16 such generations 

 in a single season. 

 About the time of the 

 first frosts in the fall 

 appears the sexual gen- 

 eration consisting of a 

 wingless male and a 

 wingless egg-laying or 

 oviparous female. The 

 males are smaller than 

 the other forms of this 

 louse, and are of a yel- 

 lowish-brown color with 

 dusky appendages and 

 cornicles. The sexual 

 females resemble in size 

 and general appearance 

 the wingless summer 

 forms, but they are dull 

 green with a tinge of 

 rusty yellow. The sexes 

 occur mostly on the un- 

 der side of the leaves. 

 They mate and the fe- 

 male then lays three 

 or four greenish eggs 

 Fig. 3. Eggs of Green on the smaller limbs of 



Apple .\piiis on Ap- ,, . ,, . 



pie Twig. the tree, generally in 



the crotches of the twigs or at the base 

 of a next-year's bud. In a day or two the 

 egg turns a shining jet black. 



The summer lice var.v considerably in 

 size and in the green shade of the body. 

 The average length of the body of the 

 wingless viviparous lice is 1.75 mm., 

 while that of the winged lice is 1.55 mm. 

 The average egg measurement is .60x.25 

 mm. 



Injury 



The Green Apple Aphis attacks leaves, 

 young shoots and fruit. When abundant 

 the lice curl the leaves badly and greatly 

 reduce the size and marketable value of 

 the fruit. 



Control 



This species can be controlled most 

 easily by the application of winter washes 

 directed against the winter eggs. Home 

 made lime-sulphur, using the 1-1-3 for- 

 mula, commercial lime-sulphur 1 to 8 

 or 1 to 10, or a 12 per cent, crude oil 

 emulsion will be found satisfactory as an 

 ovicide. The winter spray should be ap- 

 plied as late as possible before the buds 

 open, as the best results accrue when the 

 trees are sprayed just before the buds 

 begin to open. Against the lice on the 

 foliage spraying should be done directly 

 the lice have all hatched and before they 

 have had time to curl the leaves. Once 

 the leaves have been curled it will be 

 very hard to destroy the lice on them. 

 Whale-oil or fish-oil soap 1 pound to 5 

 gallons of water, kerosene emulsion 7 per 

 cent, or diluted tobacco extract (Black 

 Leaf "40" 1-1,200, Black Leaf 1-80) is ef- 

 fective. Good pressure is a requisite for 

 the spring applications. Pruning the 

 twigs in winter will destroy a large 

 number of the eggs. 



The Rosy Apple Aphis 



Aphis sorbi Kalt. 

 This species occurs on the apple all 

 over the United States. In Europe, its 

 original home, it infests also wild apples 

 (Sorhus spp.) and hawthorns. Its life 

 history is not fully known. The stem- 

 mother lice hatch at about the same 

 time as the leaves open out in the spring. 

 They feed on the under side of the leaf 

 and very soon cause it to curl around 



