44 FRUIT TREES AND THEIR ENEMIES 



for woolly aphis, with a high class burning oil, such 

 as White Rose oil, and very little damage to the 

 foliage will result; but in this case neither the heavier 

 oil (solar distillate) nor the lighter oil (petrol) must 

 be used : the latter appears to destroy the foliage 

 almost instantly. The use of undiluted paraffin — 

 even White Rose oil — on trees in leaf, must, however, 

 at present be considered a somewhat risky proceeding, 

 and one which requires further investigation : it is 

 well to apply such a drastic remedy only in cases 

 where unimportant trees are infested, and where there 

 is danger of the infection spreading to more valuable 

 ones. But if paraffin is used, it should not be diluted 

 — that is, made into a strong emulsion — under the 

 impression that there will then be less likelihood of 

 its doing damage, for the reverse has been found to 

 be the case, strong emulsions causing more injury 

 than undiluted paraffin. 



In spraying paraffin a very fine spray, such as 

 that produced by a "mistifier" or pneumatic sprayer 

 (p. 17), should be used. 



16. Paraffin emulsion. — For spraying in winter, an 

 emulsion containing 6 per cent, by volume of paraffin 

 is recommended, and no fear need be entertained of 

 any damage being done by it, so long as the buds are 

 not opening. It has already been used very ex- 

 tensively in conjunction with caustic soda {lob, loc 

 and lod), and no damage has yet been reported, even 

 in the case of peaches and nectarines ; in some cases, 

 too, it has been applied to mixed plantations when 

 the gooseberries and currants were quite green with 

 foliage, and the damage done to them was of the 



