Apple Spraying Experiments in 1916 and 1917. 121 



some days before the blossom buds showed pink, would have 

 been advantageous. However, throughout this series of ex- 

 periments, covering 8 successive seasons, no evidence has been 

 obtained to indicate that under Maine conditions the period for 

 making any single applicaton of spray for the successful control 

 of apple scab is limited to a single day, or even two or three 

 days, although the pink-bud and calyx applications should be 

 made as closely to the specified times as possible. 



ARSENATE OF LEAD AS A FUNGICIDE. 



While previous results seemed to furnish fairly conclusive 

 data relative to the fungicidal value of acid arsenate of lead in 

 preventing apple scab, these here reported represent much more 

 severe tests. In comparing plots 6 and g in 191 6, Table I, it 

 will be seen that by the use of arsenate of lead alone the amount 

 of scab on the fruit was reduced from nearly 39 to a little over 

 one and one-half per cent. This was the fifth consecutive sea- 

 son that the figures obtained from experimental tests in this 

 orchard have shown that arsenate of lead alone has materially 

 reduced the amount of scab on the fruit. Scab control on plot 

 6 in 1916 was nearly as efficient as was obtained on plot 1 where 

 the standard lime-sulphur and arsenate of lead treatment was 

 used. A more important fact which should not be overlooked 

 is that with the arsenate of lead used alone nearly twice as many 

 merchantable apples were obtained, due to the greater freedom 

 from russeting. 



A comparison of the results obtained on plots 2, 5 and 9 

 in 191 7, Table III, also indicated that arsenate of lead showed 

 considerable fungicidal value, even under the severe conditions 

 of that season. However, the results were plainly much inferior 

 to those obtained with the combined lime-sulphur and arsenate 

 of lead spray. 



ACID ARSENATE VS. "t. P." ARSENATE OF LEAD. 



No definite conclusions can be drawn from the work of a 

 single season but the records obtained in 191 7 on plots 1 and 2, 

 Table III, indicate that the "T. P." arsenate of lead possesses 

 fully as great if not greater fungicidal properties than the acid 

 arsenate since about 9 per cent less scab was obtained with it. 



