64 FRUIT TREES AND THEIR ENEMIES 



the attack is not a very severe one, and is confined to 

 small trees, the aphis may be destroyed by touching 

 the parts afifected with a paint brush dipped in 

 methylated spirits. Repeated treatment is generally 

 required to keep the aphis in check, and to prevent it 

 from spreading to other trees. 



Nursery stock, which, unfortunately, is often infested 

 with woolly aphis, should be freed from it before 

 planting. This may be done effectually by immersing 

 the stocks bodily in water at 115° for ten minutes: 

 higher temperatures may damage the trees. It must 

 be remembered that these will cool the water, and a 

 supply of hotter water should be at hand, to be added 

 as the temperature falls. Immersion for five minutes 

 in petrol (not ordinary paraffin nor solar distillate), or 

 a caustic emulsion, is almost as satisfactory. Fumiga- 

 tion with hydrocyanic acid (13) is generally recom- 

 mended for the same purpose, but, to be effective, 

 the gas must be used in the maximum quantity 

 mentioned above, or the eggs will not be destroyed, 

 and, even with every precaution, success is not always 

 obtained. 



The Leaf-curling Apple Aphis : Green Fly {Aphis 

 poini). — The eggs, which are at first yellow, and 

 subsequently black, are often to be found in great 

 numbers, clustered on young twigs ; hence, pruning 

 should reduce this pest considerably. They hatch 

 when the buds are bursting, and the insect under- 

 goes several changes of skin before it reaches the 

 mature stage. This aphis attacks the leaves, and, 

 by puncturing them, makes them curl, and causes 



