INSECTS 181 



Many other remedies for the woolly aphis have been tested, but 

 none has proved so effective as kerosene emulsion. The odor of 

 kerosene remains in the soil several months after application and 

 effectually prevents reinfestation. 



Insects affecting the Leaves 



Green-apple leaf aphis (Aphis pomi, De Geer). The green-apple 

 aphis is especially injurious to nursery stock and to young trees in 

 the orchard. The sucking of the juices of the leaves, usually on 

 the terminal growth, causes them to curl, blacken, and wither. This 

 injury to the leaves is followed by the stunting of the wood growth, 

 and on small trees which have been generally infested, the stunting 

 effect is often noticeable for years afterwards. The fruit of bearing 

 trees, when surrounded by aphis-infested foliage, practically ceases 

 to grow, the apples remaining green, hard, and gnarled for some 

 time and then dropping. 



Since the insects cannot be successfully combated after the leaves 

 have curled, the grower must resort to preventive measures. 



Treatment. The green-apple aphis passes the winter season in 

 the egg stage on the limbs and twigs of apple trees. It is possible 

 to destroy the insects at this stage and thus protect trees and foli- 

 age for the first two or three months of summer by thorough 

 sprayings with lime-sulphur solution in the late winter or the 

 early spring. 



Contact poisons must be used to destroy the fully developed 

 aphis. Because of the curling of the leaves it is practically impos- 

 sible to make applications by means of a sprayer thorough enough 

 to reach the insects beneath. It is quite a simple matter to treat 

 nursery stock and orchard trees in their first and second years by 

 dipping the infested foliage in a vessel filled with an efficient con- 

 tact poison and carried from tree to tree by hand. This is simple, 

 rapid, and more thorough than any spraying could possibly be. 

 With the disappearance of the aphids, growth is renewed and the 

 trees thrive. 



Besides kerosene emulsion, whale-oil soap, tobacco decoctions, 

 etc., a manufactured product called "Black Leaf 40" — a con- 

 centrated solution of nicotine sulphate — has come into the market 



