537 



apparently ceasing to grow at the point attacked, but which swells 

 into a ridge about the cluster of aphides. Those that appear above 

 ground can be controlled without much trouble, but the form which 

 appears on the roots and produces gall-like swellings is much more 

 difficult to extirpate. The injury to the tree is caused by the 

 sucking of the sap, which deprives it of nourishment, and by 

 poisoning of the plants, shown by the galls on the roots. The 

 damage is particularly serious in the case of young trees and 

 nursery stock. 



Among the many remedies used for the destruction of the 

 woolly aphis are Nos. 6, 14, or 20 (see pp. 490-492). A fortnight 

 after Nos. 10 or 14. The use of blight-proof stock, and No. 9 have 

 been proved the best. 



Natural Enemies The woolly aphis has very few known natural 

 enemies. The larvae of some species of laced-winged flies 

 (Chrysopidee} have often been noticed feeding upon this pest, and 

 the ladybird (Leis conformis) has been known to rid whole orchards 

 of it. 



BLACK APHIS OF THE PEACH (Aphis persica niger). 



This aphis has proven very destructive to the peach trees of 

 this State, and as it exists in .two forms, aerial and subterranean, 

 similar to the woolly aphis, its control is subject to all the per- 

 plexities of the latter aphis. It 

 attacks the leaves when they are 

 pushing in the spring, and it 

 multiplies so rapidly that it fre- 

 quently kills young trees and 

 seriously damages large branches 

 on older trees. 



When trees are badly attacked 

 by this aphis the leaves are 

 yellowish, more or less curled, and 

 spotted with fungus. 



Remedies. In winter dress the 

 soil around the stems of trees 

 with gas lime, kainit, fresh manure, 

 or No. 15. In spring spray with 

 Nos. 7, 8, 14, 18, or 20 (see pp. 

 490-492). 



Natural Enemies. The larvae 

 of several species of ' ladybirds 

 feed upon the peach aphis, as do 

 also the larvae of various species 

 of Syrphus flies. True parasites of this aphis have as yet not 

 been discovered, for the reason that the country to which the 

 aphis is indigenous has never been found. 



New growth of peach infested with 

 black peach aphis. 



