88 MAINE AGRICULTURAL EXPERIMENT STATION. I916. 



omission of the first spray 3 years out of 4 led to no material 

 difference in the results. On the other hand a like omission the 

 first year the experiment was tried meant, from the standpoint 

 of the practical orchardist, a difference between success and 

 failure in the spraying operations of the year. Where all 3 ap- 

 plications were made nearly 90 per cent of the fruit was sound 

 and perfect. Only about 50 per cent of the same grade of fruit 

 was obtained where the first application was omitted. This 

 was in 1912, a season particularly favorable for scab develop- 

 ment. The date of the first application that year, May 24, was 

 with one exception the latest since the series of experiments 

 were begun. 



Arsenate of lead as a fungicide: The apparent high fungi- 

 cidal value which this well-known insecticide has shown is one 

 of the quite unexpected results obtained. 



The first suggestion of the value of arsenate of lead for con- 

 trolling apple scab, as shown by these experiments, came in 

 1912. Then 4 pounds of the paste arsenate of lead alone in 50 

 gallons of water gave as good or better scab control than did 

 a 3-3-50 bordeaux mixture or lime-sulphur plus two pounds of 

 the paste in each 50 gallons of spray. Unfortunately no check 

 plot was saved that season, but over 3 times as much scabby 

 fruit was obtained on a plot sprayed with two pounds of the 

 arsenate of lead paste in 50 gallons of water than were pro- 

 duced where double this amount of the insecticide was used 

 alone. One possible explanation for the apparent fungicidal 

 action of the larger amount of the poison that season was that 

 the plot on which it was used was located at the corner of che 

 orchard more exposed to air and sun. This factor was elim- 

 inated in the later experiments. 



In all later work an unsprayed check plot was added and dry 

 arsenate of lead substituted for the paste form. In 1913 one plot 

 was sprayed at all 3 applications with two pounds and another 

 plot with one pound of the dry, powdered insecticide in 50 gal- 

 lons of water. Nearly 39 per cent of the apples on the unsprayed 

 plot were scabby. Almost perfect scab control was obtained with 

 bordeaux mixture, the larger amount of the arsenate of lead 

 used alone, and lime-sulphur 20 per cent stronger than stand- 

 ard dilution — the efficiency being in the order named. Some- 

 what poorer results were obtained with standard dilution lime- 



