16 EXPERIMENTS ON THE APPLE WITH SOME NEW FUNGICIDES. 



particularly the lime-sulphur plat, its real competitor in efficiency. 

 In the case of the Yellow Newtown, the slightly greener color might 

 not be objectionable. With the York Imperial it was not sufficiently 

 marked to be important. On the Ben Davis it might possibly be 

 slightly objectionable, unless by allowing the fruit to hang later it 

 eventually attained full color. 



On plat 7 the new form of copper sulphid gave entirely satisfactory 

 results on both fruit and foliage of the Yellow Newtown and the York 

 Imperial varieties. It gave excellent results on the foliage of the 

 Ben Davis, but russeted the fruit about 10 per cent — that is, one-sixth 

 as much as standard Bordeaux mixture. Under the conditions at 

 Winchester the new copper sulphid was almost, if not quite, abso- 

 lutely harmless on the Yellow Newtown and the York Imperial, and 

 this is the only copper spray of which this could be said. If these 

 results can be depended upon in the future, this spray could be used 

 commercially with excellent success. The 10 per cent of russeting of 

 the Ben Davis would entirely prohibit its use on that variety if the 

 self-boiled lime-sulphur and the iron sulphid prove as efficient as 

 indicated by this experiment. The percentage of russeting on the 

 Ben Davis might possibly be reduced by cutting down the amount 

 of copper from 2 pounds to 1 pound, or even to one-half pound. Fur- 

 thermore, this copper sulphid may prove to be noninjurious on the 

 Ben Davis fruit after it has reached a certain stage of growth. We 

 may say, therefore, that we have in the copper sulphid the least 

 injurious form of copper, and if copper is absolutely necessary for 

 ultimate success in controlling the most difficult diseases, this form 

 of spray produces the minimum amount of injury. 



One of the surprises of this experiment was the remarkably good 

 result obtained from the arsenate of lead plat, it showing entire 

 freedom from russet injury. Under the rather easy conditions in 

 regard to fungous infection prevailing at Winchester during the 

 season in question arsenate of lead proved efficacious in preventing 

 fungous diseases. It is certain that under more adverse conditions 

 this freedom from fungi can not be depended upon to the extent 

 indicated in these experiments. 



The efficiency of the arsenate of lead cast some doubt as to whether 

 it was not concerned in the success of the self-boiled lime-sulphur 

 and the iron-sulphid plats, and perhaps some of the others, since it 

 was added to all of the mixtures used. Self-boiled lime-sulphur, 

 however, has been successful in several of Mr. Scott's experiments on 

 the apple, and still more so on the peach, and it is now recognized 

 as the standard fungicide for the summer treatment of peach diseases. 

 An iron sulphid somewhat similar to this one, made with the sulphur 

 solution, in the experiments of Mr. W. H. Volck, at Watsonville, 

 Cal., on the powdery mildew of the apple, proved superior to Bor- 



[Cir. 58] 



