14 



BULLETIN 866, U. S. DEPARTMENT OF AGRICULTURE. 



gave as good results as the Bordeaux sprays containing 1.25 per cent 

 of copper sulphate. In fact, all of the sprays gave practically the 

 same results. The only plats giving yields below 240 pounds were 

 the two check plats and the one treated with copper sulphate and 

 lead arsenate. The yield and blight readings were practically the 

 same for the plats sprayed with the Pickering solution as for those 

 sprayed with Bordeaux mixture (Plate II, fig. 1). 



In Central Maine. — Separate plats of about % acre each of Green 

 Mountain and Rural New Yorker seed potatoes, in Foxcroft, Me., 

 were treated with Pickering and barium-water sprays of 0.7 per cent 

 copper sulphate content, and with reduced lime Bordeaux, 4-4-50, 

 4-2-50, and 4-1-50, sprays. The rest of the 8-acre field was sprayed 

 with a standard Bordeaux, 5-5-50. Plats sprayed with standard 

 Bordeaux were placed between the experimental plats. A spray 

 wagon treating six rows at a time was used. As the vines were not 

 sprayed until July 15, they were double sprayed at each spraying, or 

 four times altogether. The results of these tests are given in Table 4. 



Table 4. — Effect of various sprays on late blight and yield of potatoes (Central Maine, 



1918). 



Plat 

 No. 



l.. 

 2.. 

 23.. 

 4.. 

 5.. 



Spray used. 



Pickering (A) 



Barium water 



Bordeaux, 4-4-50. 

 Bordeaux, 4-2-50. 

 Bordeaux, 4-1-50. 

 B ordeaux , 5-5-50 . 



Copper 

 sulphate 

 in spray. 



Per cent. 

 0.7 

 .7 

 1.0 

 1.0 

 1.0 

 1.25 



Green Mountain. 



Blight on 

 vines. 



Per cent. 

 Trace. 



..do 



..do 



..do 



..do 



..do 



Yield.' 



Pounds. 

 331 

 322 

 285 

 338 

 381 

 258 



Rural New Yorker. 



Blight on 

 vines. 



Per cent. 

 Trace. 



...do 



...do 



...do 



...do 



...do 



Yield, i 



Pounds. 

 324 

 332 

 285 

 333 

 319 

 330 



1 Obtained from two rows, 150 feet long. 



2 A ledge or rock in this plat. 



On the whole, the blight results were uniform and very low. Early 

 in August a trace of blight appeared through this and other fields, 

 but the dry August practically put an end to it. The yields of Green 

 Mountain tubers varied somewhat, particularly at the lower end of 

 the field where plats 5 and 6 were located, but plats 1, 2, and 4 gave 

 practically the same yields. The Rural New Yorker potatoes were 

 grown on a more uniform portion of the field, so that they showed 

 uniform results, except in plat 3, where a ledge of rock reduced the 

 yield. Only traces of blight were seen on the Rural New Yorker 

 vines, which are much more rangy and stand up from the ground 

 higher than the Green Mountain vines, making them less liable to 

 infections of late blight. 



BARIUM-WATER SPRAYS IN 15116. 



It was thought that the greater solubility of barium hydrate over 

 lime might be an advantage in the preparation of a spray like the 



