190 MAIXE AGRICULTURAL EXPERIMENT STATION. I915. 



factors were particularly favorable for scab infection at the 

 blossoming period. Hence the results secured by omitting the 

 first fungicidal spray were most striking. Three applications of 

 standard dilution lime-sulphur gave almost perfect scab control, 

 there being only 1.4 per cent of affected fruits at harvest time. 

 Where the first of these applications was omitted 47.6 per cent 

 of scabby apples were obtained. However, even here the 

 amount of scab was materially reduced, but this can only be 

 judged approximately, for the only available check plot was one 

 sprayed with 2 pounds of arsenate of lead paste (approximately 

 equivalent to one pound of the dry powder used during the past 

 2 seasons) in 50 gallons of water. Somewhat over 80 per cent 

 of the fruit on this plot was scabby at harvest time. Our work 

 during that season and the two following has shown that double 

 this quantity of arsenate of lead is of material value as a fun- 

 gicide for apple scab. Also the results obtained in 1913 indi- 

 cated that even so small an amount of arsenate of lead as was 

 used on this so-called check plot in 1912 might materially reduce 

 the amount of scab and consequently make a plot sprayed in 

 this way unreliable as a basis for comparison in judging the 

 efficiency of a fungicide used on another plot. 



Different dilutions of lime-sidphur. Last season was the 

 third where different dilutions of lime-sulphur were tested, in 

 which apple scab developed to a sufficient extent to judge their 

 efficiency. Earlier work indicated that under Maine conditions 

 it was not safe to use a weaker dilution than that commonly 

 employed, or what is referred to throughout this publication as 

 "standard dilution." From the work of the three seasons it 

 would seem that on the Ben Davis, a variety well-known to be 

 easily injured by bordeaux mixture, at least 20 per cent more of 

 a lime-sulphur concentrate than is commonly employed may be 

 used to make a given amount of spray and be used with com- 

 parative safety. 



With this stronger dilution a slight amount of leaf injury 

 has been observed occasionally and the amount of fruit russet- 

 ing has been somewhat increased, particularly last season where 

 it was increased from 4.63 to 7.06 per cent when compared with 

 the plot sprayed with the weaker dilution. Therefore there 

 might be some question about using the stronger spray for the 

 later applications. 



