56 



EtllCYCLOPEDIA OF PRACTICAL HORTICULTURE 



plants as the Corn-root Aphis. It is about 

 one-twelfth of an inch in length, bluish- 

 green and without bloom. It migrates 

 from weeds to cultivated host-plants in 

 summer and when abundant stunts the 

 plants and causes the leaves to wither 

 and finally die. Injury is heavier on 

 broom-corn and sorghum than on corn. 

 In Texas it has been found on barley in 

 winter. Little seems to have been done 

 on the control of this louse. Whale-oil 

 soap 1 pound to 5 gallons will destroy 

 the aphis, but it is doubtful if this would 

 be practicable in the field on large areas. 



SMALL GRAINS 



Three species of plant-lice, all Euro- 

 pean, are injurious to small grains. These 

 are: (1) the English Grain Aphis 

 (Macrosiphum granarium Buckt.) ; (2) 

 the Spring Grain Aphis (Toxoptera 

 graminum Rond.); (3) the European 

 Grain Aphis ( Aphis padi L.). These are 

 all bright green forms, the first-named 

 being considerably larger than either of 

 the other two. In the warmer parts of 

 the United States they produce parthen- 

 ogenetically all the year around on grains 

 and grasses, but In the North winter is 

 passed in the egg stage. The injury they 

 do to young grain plants is often severe, 

 and grain should be watched for their 

 appearance. Small localized outbreaks 

 may be controlled either by plowing un- 

 der, by covering the spots with straw 

 and burning, or by spraying with whale- 

 oil soap (1 pound to 10 or 12 gallons of 

 water). On large areas of infested grain 

 the only known methods of control are 

 the suppression of all volunteer wheat 

 and oats in the fall, late sowing of fall 

 wheat, and fertilization of the soil to 

 help the plants to resist attacks. 



POTATO 



Tlie Potato Apliis 



Macrosiphum solatiifolii Ashmead 



This is a large green plant-louse which 

 is occasionally very injurious to the po- 

 tato in the eastern states. The aphid 

 passes the winter on Shepherd's Purse 

 and other weeds, migrating in spring 

 and summer to the potato and returning 

 in the fall to the weeds. The usual con- 



tact insecticides (whale-oil soap, oil emul- 

 sions and tobacco extracts) are not prac- 

 ticable against this louse on a large scale, 

 but they may be employed with success 

 on a small patch. Control on a large 

 area is reduced to clean culture, fall 

 plowing and the burning over of weedy 

 places in the vicinity of potato fields in 

 order to clean up the land of the alter- 

 nate host-plants of the aphis. 



HOP 



The Hoi) .Vpl'is 



Phororion humuli Schrank 



This is a light green non-pulverulent 

 louse originating in Europe and now dis- 

 tributed all over the United States. The 

 winter is passed in the egg stage on 

 plums and prunes, wild and cultivated, 

 the lice migrating in spring to hops. In 

 California researches would indicate that 

 the aphis may pass its whole annual life 

 cycle on the hop. as plums growing in 

 the vicinity of hop-yards badly infested 

 have been carefully examined and found 

 to be totally uninfested by the winter 

 eggs. This plant-louse may be destroyed 

 by suraving with tobacco extract (Black 

 Leaf 1-2.000 to 1-3.000) combined with 

 flour paste (4 pounds to 100 gallons 

 water). 



W. M. DAvmsoN 



Apple 



HISTORY AM) ORIGIN 



The histor.v of the apple is an interest- 

 ing illustration of modification through 

 artificial selection. Its history before the 

 period of its domestication is unknown. 

 The best we can do is to point to the 

 wild ancestor and say. "Here is where 

 our particular variety had its origin." 



Since the period of its cultivation, how- 

 ever, the changes have been rapid and 

 always in the direction best suited to 

 the wants of mankind. We have studied 

 the habits, adaptations, wants, likes and 

 dislikes of fruits, and more especially the 

 apple, because it is the "King of fruits," 

 and have reduced this study to more or 

 less of a science. We have systems of 

 experimentation and discovery which tend 



