APPLE INSECTS 145 



judicious pruning, especially on young trees. Nursery stock is 

 frequently badly infested, and the dormant trees may be heavily 

 stocked with the eggs. It is sometimes practicable to crush 

 the eggs on a few young trees with the fingers or a thin wooden 

 paddle. The eggs are very resistant to the strongest contact 

 insecticides, like oils and soaps. Experiments indicate that 

 spraying to kill the eggs is of doubtful utility, usually enough 

 eggs hatching to 

 abundantly stock 

 the trees with 

 aphids. Thorough 

 fumigation with hy- 

 drocyanic acid gas 

 is said to kill many 

 of the eggs. 



After the aphids 

 hatch in the spring, 

 they are readily 

 killed when hit with 

 ^' Black Leaf 40" 

 tobacco extract, f 



of a pint in 100 gal- ^^^ 



Ions of water, add- u^,, ..y m..,.+ i; i . • , 



' j^itf. lo/. — riant-lice clustering on a young apple. 



ing 3 pounds of soap 



to each 100 gallons to make the liquid stick and spread better. 

 One thorough application when the aphids are thick on the 

 opening buds will usually control the more common apple bud 

 aphis, S. avence, which as a rule does not curl the leaves as 

 much as the other species. The apple leaf aphis and rosy apple 

 aphis, however, breed on the trees longer and often curl the 

 leaves, so that it is almost impossible to hit a majority of them 

 with the spray. Nurserymen often dip the infested branches 

 into the insecticide (Fig. 156), thus doing more effective work 

 than can be done with a spray. Several dippings or sprayings 



