162 



Insect Pests. 



Wye College, and these bore out what Mr. Chapman had found ; 

 check trees in both cases being kept. Still more definite results 

 were obtained by Mr. J. H. "W. Best of Suckley, and Mr. Montague 

 Taylor of Shelsley Walsh, and Mr. Martin of the Toddington Fruit 

 Grounds, crops of apples being obtained by the former, for the 

 first time for many years, on the treated trees, while the rest of the 

 plantations suffered as usual. 



Where failures have taken place such as recorded by Mr. Spencer 

 Pickering (10), and notified to me by Mr. Harriett of Sittingbourne, 



the cause was probably be- 

 cause the wash was not put 

 on thick enough.* 



The wash does not do 

 any such impossible thing as 

 corrode the egg-shells, it acts 

 as far as I can see as a 

 mechanical barrier to the 

 escape of a very large number 

 of the young. At the same 

 time it is possible that the 

 salt has some osmotic power, 

 for where the quantity of 

 salt is increased the action 

 becomes greater. Observers 

 have noticed that when trees 

 are thus treated the Psylla 

 ova assume a dull leaden hue, 

 and this still further points 

 to some change taking place 

 in the ova. The addition of 

 waterglass is to prevent the wash from flaking off. Many sub- 

 stances have been tried for this purpose, both by Mr. Spencer 

 Pickering and myself, and the same results have been attained; 

 waterglass or paraffin being the only substances found to do good 

 in this respect. The latter, however, I found much inferior to the 

 former. 



Spraying when the suckers are in the trusses of the blossom may 

 do a little good if the blossoms are hit fairly hard so as to drive 

 the liquid in, but this may do some harm, and but few are actually 

 touched by the spray owing to their waxy and thready coverings. 



FIG. 135. SEXECA NOZZLES USED FOR LIME AND 

 SALT WASH. 



A, set for spraying. B, opened to blow out lime 

 when blocked. 



* In the former I now learn this was the case. 



