FRUIT TREES AND THEIR ENEMIES 165 



detected. Pruning off and destroying all 

 shoots in which eggs have been deposited is 

 the usual course of treatment before hatching 

 has commenced. When the caterpillars ap- 

 pear they may be readily collected in the webs 

 in which they congregate when not feeding 

 and during dull weather. Spraying with 

 Abol insecticide will kill the caterpillars, but 

 the eggs resist even the most powerful winter 

 washes. This pest has also been referred to 

 when dealing with forest trees. 



Aphis, several species, attack the leaves of 

 fruit trees, the most persistent being the leaf- 

 curling aphis (A. pomi\ the rosy-leaf aphis 

 (A. sorfa), and the blossom and leaf aphis 

 (A. fitchii}. The two former, by attacking 

 the leaves, cause them to curl up, and to be- 

 come discoloured and sticky with excreta from 

 the insect's body. The red or yellow colour 

 of the injured leaves has given the popular 

 name to the rosy-leaf aphis. Spraying with 

 weak paraffin emulsion about the end of April, 

 before the leaves curl up, is to be recommended. 

 Autumn spraying with strong paraffin emul- 

 sion has also proved successful in dealing with 



