68 Bulletin 140. 



This spraying was given to all plats except No. 39, which was left 

 as a check. On this plat no treatment was given except for the potato 

 beetle, the Pans green applied being mixed with plaster. By reference 

 to the table on page 56 it will be seen that on plat 39 the yield of 

 potatoes was only 234 bushels per acre, while on the adjacent plat, 

 No. 40, treated exactly the same as plat 39, except the spraying, the 

 yield of potatoes was 305 bushels per acre. In this case the sprayed 

 plat gave an increase of 7 1 bushels per acre over the plat not sprayed. 

 The average total yield of all plats sprayed and given level culture was 

 337 bushels per acre and of the plat receiving no spraying 234 bushels. 

 The only reason we can ascribe as the cause of the low yield on the 

 plat not sprayed is that owing to the attack of the blight the vines 

 died three weeks earlier than did those on the sprayed plats. 



The necessity for thorough work should be emphasized. The foHage 

 must be thoroughly covered with a coating of the Bordeaux mixture 

 so that spores of the blight will not readily find a lodging place. If 

 the spraying is done in a careless manner it may nearly as well not be 

 done at all, as it will not accomplish the purpose. Even with the 

 potatoes on the experimental ground where the spraying had been 

 thoroughly done the blight struck them about the ist of September, 

 and no doubt lessened the yield somewhat. It was, however, so late 

 in appearing that no opportunity was offered for the disease to attack 

 the tubers and produce the rot. Had another spraying been given 

 about August 25, it is probable the time of growth would have been 

 lengthened and more satisfactory results obtained. There appears to 

 be a difference in the ability of different varieties to withstand attacks. 

 With us the Carman No. 3 possessed the greatest power of resistance, 

 and the Rose of Sharon was most susceptible to the disease. In all 

 cases the seed used should be from stock not attacked by blight, as it 

 is possible the disease may be carried over in affected tubers. 



One Acre Potato Field. 



In addition to the series of experimental plats which have been 

 described, one acre of potatoes was planted on the land where 314 

 bushels of potatoes had been harvested in 1S96. Previous to 1896 

 this land had been subjected to a regular four years' rotation of wheat, 

 meadow, corn and oats. In the fall of 1895 a light application of 

 strawy manure was applied, and then the straw was all raked off in the 



