June 1893.] 



INJUBIOUS INSECT8 AND FUNGI. 



effective, both as a preventive of the potato disease, and as a 

 remedy against it when it has appeared. Many potato growers 

 are so convinced of the vahie of this treatment that they intend 

 to spray their potato plants systematically, as a part of ordinary 

 cultivation, at certain stages of their growth, whether tliere is 

 disease upon them or not. 



There are horse-machines well adapted for distrihuting the 

 sulphate of copper solution evenly and in a fine : spray over and 

 under the leaves of the plants, taking seven or eight rows at a 

 time. From eight to 10 acres can be sprayed in a day by these 

 machines, whose makers sell them and let them out on hire. 

 Smaller horse-machines, which are suitable for small occupations, 

 have been recently adapted to take three rows only. 



The formula for the preparation of sulphate of copper solu- 

 tions, or, as it is termed, bouillie bordelaise, is 20 lbs. of sulphate 

 of copper, 20 lbs. of lime, and 100 gallons of water. Some put only 

 10 lbs. of lime to 20 lbs. of sulphate of copper, but it has been 

 shown by M. Girard and other experimenters that 20 lbs., or 

 at least 15 lbs., of lime is preferable to the smaller quantity 

 mentioned, because it is essential to neutralise completely the 

 acid in the sulphate of copper, or the solution will burn the 

 leaves of the plants. It is important also, for this reason, that 

 the lime should be pure, and this applies equally to the sulphate 

 of copper. 



Some recommend that 20 lbs. of treacle or molasses should be 

 mixed with 20 lbs. of sulphate of copper, 20 lbs. of lime, and 

 100 gallons of water, as they hold that the syrup causes tlie 

 solution to adhere to the leaves. In several cases last year 

 where this di^essing was tried side by side with the ordinary 

 sulphate of copper solutions no apparent difference was remarked. 

 The cost of spraying varies according to circumstances, from 

 78. 6d. to 108. per acre for each application. 



It will be interesting here to give some extracts from the Report 

 on Experiments on Potatoes carried out by the Technical Educa- 

 tion Committee of the Wilts County Council in 1894, to show the 

 advantages of spraying for preventing disease. Twenty-four 

 different varieties were grown, and sprayed twice, on June 25th 

 and J uly 26th, with a solution of 20 lbs. of sulphate of copper and 

 10 lbs. of lime to 100 gallons of Avater. A few days previous to 

 the second spraying, disease spots were noticed over an entire 

 plot of Imperators, whilst all the central plots not sprayed were 

 more or less affected. The weather was very suitable for the 

 propagation of the disease and much damage had already been 

 done to the crops generally in the district at the time of the 

 second spraying. By August 13th, several of the unsprayed plots 

 had entirely lost their haulm, and on September 1st, Schoolmaster, 

 Supreme, and many second early varieties were still green on the 

 unsprayed areas, whilst on September 13th the later varieties 

 seemed hardly touched with the disease, although at this latter 

 date the haulm on the central plots had disappeare.d, In the case 



