SPRAYING PROBLEMS 141 



left a grim page in the history of these islands. In 

 1845 Sir Robert Peel received an account in August 

 of an extraordinary appearance of the potato crop in 

 the Isle of Wight; these signs were soon observed 

 throughout the south-eastern counties. The crops 

 were almost entirely destroyed. Alarming accounts 

 were received from Ireland, where the potato was 

 almost the chief article of food and the means of 

 obtaining other food. Dr. Lindley and Dr. Playfair 

 were sent to Ireland to investigate the malady. 

 Indian corn to the value of ; 1,000,000 sterling was 

 sent to alleviate the distress, without avail. The great 

 potato failure of 1846 brought in its train ruin, star- 

 vation, and death to many thousands. It has been 

 described as one of the greatest calamities which ever 

 afflicted the human race. 



Through the allotment movement of 1917 the men 

 and women of Britain became amateur gardeners and 

 cultivators of the potato. The present year brings 

 with it the prospect of an extensive use of potato flour. 

 The production of 6,000,000 tons of potatoes is aimed 

 at. The risk of serious loss through an epidemic 

 of potato blight is correspondingly increased at a 

 time when we cannot afford to take risks, at a time 

 when it is imperative to reach high-water mark in 

 food production. 



The methods adopted in fighting plant pestilences 

 are somewhat analogous to those used in actual war. 

 The parasite must be attacked at a vulnerable point 

 or moment. 



In the case of a " naked" aphis, your spray com- 

 pares with rifle and machine-gun shooting, except 

 that the insects are killed either by suffocation or 

 poisoning. 



Again, in the case of the limpet-like San Jose scale, 

 and other insects which pass the winter as a young 



