44 



INJURIOUS INSECTS AND FUNGI. 



[Sept. 1894. 



with compositions of sulphate of copper and lime has been 

 employed preventively with satisfiictory results in most cases 

 in seasons of disease ; but the treatment has not an unbroken 

 record of success, and in a few instances the application of these 

 compositions to potato plants has even appeared to have an 

 injurious effect upon the yield. 



On the whole, however, there is ample evidence to prove that 

 potato-plants dressed with sulphate of copper compositions offer 

 much more resistance to the attacks of the potato-disease fungus 

 than plants not so treated. It has also been demonstrated that 

 when potato-plants have been attacked by this fungus, the treat- 

 ment with sulphate of copper compositions has proved remedial 

 in a considerable degree, and has in many instances arrested the 

 progress of the disease. 



M. Girard — the greatest authority upon this subject — observes 

 that it is most imprudent to wait until disease has appeared 

 before the sulphate of copper compositions are applied, because 

 the fungus spreads with such rapidity in favourable circum- 

 stances, that the cultivators have not time to organise and carry 

 out defensive measures. . Treatment should be adopted as a 

 means of prevention, even if there may not be actual disease. 

 In short, treatment is insurance against disease ; but it must 

 be remembered that the results, both preventive and remedial, 

 depend in a very great degree upon the time and manner of 

 application, as well as the nature, preparation, and distribution 

 of the compositions. 



Compositions, 



The most commonly adopted composition consists of — 

 20 lbs. of sulphate of copper. 

 10 lbs. of lime. 

 100 gallons of water. 

 This has been found strong enough for all purposes, and does 

 not injure the foliage if it is properly and evenly distributed, 

 and not applied to very young plants. 



A weaker composition is sometimes used, made of — 

 15 lbs. of sulphate of copper. 

 7^ lbs. of lime. 

 100 gallons of water. 

 This is preferred by some observers, especially for potato- 

 plants whose leaves are young and tender. In experiments in 

 Ireland last year, it was found that this composition was not so 

 effective for treating Champion potatoes, whose leafage is coarse, 

 as that made with 2 per cent, of sulphate of copper. 



Another composition is advocated by M. Girard, consisting 

 of— 



20 lbs. of sulphate of copper. 



20 lbs. of lime. 



20 lbs. of molasses. 



100 gallons of water. 



