BASIC COPPER SILFATE AS A FUNGICIDE 139 



Potatoes 



A spraying experiment was conducted on a 3.55 acre strip on the Farm field 

 north 1, under the supervision of M. H. Cubbon, to determine the relative effec- 

 tiveness of low and high basic sulfates (lots G and 7) and Bordeaux 4-4-50 in 

 controlling early and late blights on potatoes. The field was undulating from east 

 to west and suffered from excessive water in the dips. It was divided into 2 sec- 

 tions (150 by 495 feet), east and west, of 13 four-row plots each. The east half 

 was evidently more uniform than the west. The entire field was manured at 

 the rate of 15 tons to the acre, and in addition the east half received 1100 pounds 

 an acre of a high commercial fertilizer and the west half 600 pounds of the same 

 mixture. The seed was certified Green Mountain disinfected with corrosive 

 sublimate. The potatoes were planted on May 14 and 15 at the rate of 25 bushels 

 an acre on the two southern rows of each plot 1 to 9 inclusive and 15 bushels an 

 acre on the northern rows of plots 1 to 9 and all rows of plots 10 to 13 inclusive. 

 The crop was harvested between September 17 and October 10. The basic sul- 

 fates with linseed oil 0.50 pt.-50 were applied at a concentration of 0.24 per cent 

 copper, the same as Bordeaux 4-4-50 and with lead arsenate 2-50 when necessary. 

 Chemical hydrated lime was used in preparing the Bordeaux. A "Gray Jacket" 

 traction field force pump with a 100-gallon tank, under 200 to 300 pounds pressure, 

 and a boom covering 4 rows, 3 nozzles to a row, was employed. The amount of 

 spray varied somewhat with the pressure from 100 to 135 gallons an acre. The 

 plants were slow in starting but made a fair growth considering the season. The 

 vines were sprayed practically every week as long as the tops continued green, 10 

 treatments. Doran observed some early blight and tipburn on August 10 and 

 late blight on August 17. Insects were not a limiting factor (Bourne). The yield 

 records were determined from the 2 middle rows of every plot. 



On 25 out of 28 plots the fungicides reduced the amount of rot. The Bordeaux 

 was the most effective followed by high and low basic sulfates. The extreme 

 variations in results due to inequalities m soil, natural drainage, excessive rainfall, 

 etc., warrant only general deductions as to trend. The Bordeaux was unquestion- 

 ably superior to the basic sulfates probably due to its greater dispersion. 



Dusting experiments were conducted on the Station rotation 0.08 acre plots 

 Nos. 51, 54 and 57 and on the west half of Field B 0.205 acre plot, under the super- 

 vision of J. P. Jones, to determine the relative effectiveness of low and high basic 

 sulfates and a commercial monohydrated copper sulfate-hydrated lime dust 

 in controlling early and late blights on potatoes. On plot 51 potatoes alternate 

 every other year with onions and on plot 57 with tobacco, while on plot 54 potatoes 

 have been grown continuously for five years. These plots received the equivalent 

 of 2500 pounds of 5-8-7 fertilizer an acre. The northern portion of the west 

 half of Field B was in potatoes in 1927 and the southern portion in mangels. Field 

 B received approximately the equivalent of 2000 pounds of 5-8-7 fertilizer an 

 acre. The seed was certified Green Mountain disinfected with corrosive sub- 

 limate. The potatoes were planted on May 10 and harvested on September 14 

 when the vines were nearly dead. The growth during the entire season indicated 

 . adequate fertilizer treatment. The vines remained green longer than usual in 

 spite of late blight, probably because tipburn injury was negligible (Jones). 

 The basic sulfates (lots 6 and 7) were mixed with a free-flowing talc, with and with- 

 out lead arsenate, and contained 5.41 per cent copper and 4.00 per cent arsenic in 

 the first instance and 6.80 per cent copper in the latter. The commercial copper- 

 lime dust was guaranteed to contain 6.80 per cent copper ' and when mixed with lead 

 arsenate was calculated to contain 5.41 per cent copper and 4.00 per cent arsenic. 



'Actually tested 7.70%. 



