52 



ENCYCLOPEDIA OP PRACTICAL HORTICULTURE 



shoots of plums in spring. The stunting 

 effect of its injury is sometimes very no- 

 ticeable on the trees. The summer gen- 

 erations live on grasses. 



CHERRY 



The Black Cherry Aphis 



Myzus cerasi Fabr. 

 This is a jet black shiny louse with 

 long slender black cornicles. It infests 

 chiefly the heads of young shoots and is 

 often very injurious, checking consider- 

 ably the growth of the tree. The life his- 

 tory and control are similar to those of 

 thC'Green Apple Aphis. 



PEACH 



The Green Peach Aphis 



Myzus persicae Sulz. 

 The majority of the individuals are 

 green or green with black markings, but 

 some are pink, reddish-brown or yellow. 

 This louse measures about one-tenth of 

 an inch in length. No other aphid with 

 such a wide range of food plants as the 

 Green Peach Aphis is known. Its food 

 plants include nearly all deciduous fruit 

 trees, nearly every vegetable, many 

 greenhouse plants and numerous weeds. 

 In Colorado and Missouri it is often quite 

 harmful to peaches and other stone fruits, 

 but on the Pacific Slope it is rarely in- 

 jurious to fruit trees. The life history 

 is somewhat similar to that of the Rosy 

 Apple Aphis, in that the third generation 

 migrates from fruit trees to weeds, veg- 

 etables and greenhouse plants. In the 

 fall occurs a return migration to the 

 fruit trees on which the winter eggs are 

 deposited. In California viviparous lice 

 may be found throughout the year on 

 weeds and in greenhouses. The princi- 

 pal injury occurs to fruit trees in the 

 spring, the lice feeding on the young 

 fruit buds and weakening them to such 

 a degree that they finally shrivel and fall 

 off. Later the foliage will be curled by 

 the lice feeding thereon. 



Control 



As the lice hatch fully two weeks 

 before the buds open a winter wash may 

 be applied very successfully at this time. 

 The winter sprays recommended for the 



Green Apple Aphis are successful in com- 

 bating this aphis. Black Leaf "40", 1 

 to 1,000, or Black Leaf, 1 to 70, is also 

 effective. After the trees are in foliage 

 the tobacco extracts may be used effect- 

 ively, but spraying should not be delayed 

 too long as the lice are very hard to 

 reach once the leaves are curled. 



The Black Peach Aphis 



Aphis persicae-niger Smith 

 This is a native American species dis- 

 tributed all over the United States. Both 

 winged and wingless viviparous females 

 are shining black and the young lice are 

 brown. The louse infests roots as well 

 as the aerial portion of the tree. Its 

 life history is somewhat similar to that 

 of the Woolly Apple Aphis. In winter 

 only the wingless root forms exist. Some 

 of these migrate upward in late spring 

 and found colonies on the leaves and 

 shoots. These colonies remain through- 

 out the summer, the winged individuals 

 migrating to other trees. The sexed 

 forms are as yet unknown. The root 

 form occurs chiefly on the smaller and 

 more tender roots and thrives best on 

 light sandy soils. 



Control 

 The aerial lice ma.v be controlled by any 

 of the contact insecticides suggested for 

 the Green Apple Aphis. For the root 

 form the surface soil above the roots 

 should be scraped away and tobacco dust 

 applied. This will be leached down by 

 the rain. 



CURRA>TS \yn GOOSEBERRIES 



The Currant .\phis 



Myzus ribis L. 

 This is a small green or yellow louse 

 with black markings which curls the 

 terminal leaves of the shoots of currants 

 and gooseberries. Its life history is sim- 

 ilar to that of the Green Apple Aphis. 

 As the lice collect on the under side of 

 the leaves it is necessary to use an under- 

 spray nozzle to reach them. Any of the 

 contact sprays suggested for the Green 

 Apple Aphis may be used but applica- 

 tions should be made before the leaves 

 are badly curled. Very often hand-pick- 

 ing of the curled leaves will suflSce to 

 clean up this pest. 



