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SPRAYING FOR APPLE SUCKER (PSYLLA MALI). 



By F. R. PETHERBRIDGE, M.A. 



(School of Agriculture, Cambridge University.) 



It is a common practice among fruitgrowers to spray their apple 

 trees at the time when the buds are bursting, in order to check the 

 ravages of the apple sucker. It is supposed that the washes applied 

 prevent the eggs from hatching. Some experiments 1 were carried out 

 in 1914 by the writer to try and find out how much good the various 

 washes did in this connection. 



The following experiments are a continuation of this work in more 

 detail. 



The experiments were carried out in one of Messrs Chivers and Sons' 

 orchards. Each plot contained ten apple trees alternated with plum 

 trees, and was separated from its neighbour by a row of plum trees. 

 The trees were about twenty years old and all of the variety Keswick 

 Codling. 



At the end of February the number of apparently fertile apple 

 sucker eggs were counted on certain twigs. A twig was chosen on each 

 of three trees on every plot. The twigs were as similar as possible and 

 were situated on the outside of the trees in order to prevent insects 

 from falling from above. They were thickly covered with eggs, each 

 carrying about 500. 



A high pressure spraying machine was used for making the applica- 

 tions, and special care was taken to cover all the eggs which had been 

 counted. It should be noted that on many of the trees, although care- 

 fully sprayed, about 20 % of the eggs were untouched by the spray. 

 Observations were also made in the orchards of other growers, and it 

 was found that a considerable proportion of the eggs are not covered 

 by the spray fluids used. 



1 Jour a. Board of Agric. Jan. 1916. 



