1907.] The Winter Spraying of Fruit Trees. 623 



Ground limestone should contain a rather larger percentage 

 of fine powder, as the finer the grinding the greater will be its 

 activity in the soil. It should also contain a high percentage of 

 carbonate of lime. When the purer limestones are used for the 

 preparation of ground limestone, the percentage of carbonate 

 of lime may be expected to exceed 95 per cent. 



Since November, 1905, various experiments have been carried 

 out with Insecticides by Mr. W. E. Collinge, of the Department 

 of Economic Zoology, of the University of 



SprayinJ^of^Fpuit ^^^"^^"S^^^^^' amongst these was one 

 Trees. undertaken for the purpose of finding a 



more effective winter spray-fluid for destroy- 

 ing the eggs of the Mussel Scale, Plum Aphis, and Apple 

 Sucker, three well-known insect pests in the Midland Counties,, 

 which annually cause serious losses to fruit-growers. 



In connection with these experiments, it was found in spra}^- 

 ing the eggs of the Apple Sucker with soda and potash that 

 whilst it sometimes happens that the eggs are not all killed, all 

 the experiments go to prove that if the spray-fluid is properly 

 made and applied, and does not contain too much soft soap, com-^ 

 paratively very few of the eggs hatch out. It seemed desirable 

 to institute trials with a view to obtaining a more effective 

 .spray-fluid, and experiments were first made with caustic soda 

 and soft soap, but these proved unsatisfactory. A number of 

 laboratory experiments were next made with various strengths 

 of caustic soda, mixed with varying quantities of paraffin 

 emulsion. Nearly all of these pointed to the fact that a strong 

 solution of caustic soda and paraffin emulsion was effective, and 

 the percentage of eggs killed rose with the strength of the 

 spray-fluid up to a certain point. 



Out-of-door experiments were then commenced in March,, 

 1906, with the following spray-fluid 



Caustic soda (98 per cent) 

 Soft soap ... 

 Paraffin 

 Soft water... 



The soft soap was dissolved in a gallon of boiling water, and 

 whilst still hot the paraffin was added and beaten up into 



2 lb. 



4 lb. 



5 pints. 

 :o gallons. 



