PREVENTION OF RUSTS. 67 



sulphate, cupric ferrocyanid, cupric hydroxid, ])otassium sulphid, 

 flowers of sulplmr, and sulpliosteatite powder. Treatments were 

 given when the plants were 2 to 4 inches high in the fall and con- 

 tinued until Mav 16 — seventeen treatments in all. 



In June, in spite of all these treatments,- "not a leaf could be found 

 that did not show the fungus." The treatments, furtliermore, had 

 no appreciable effect on the yield. Under Galloway's direction, 

 Swingle performed similar experiments in Kansas the same year 

 ^vith Bordeaux mixture, ammoniacal copper carbonate, and j)otas- 

 sium sulphid. In liis experiments "Bordeaux mixture did to a 

 considerable extent prevent rust, but the other preparations had 

 little or no effect on the disease. In no case did the prevention of 

 rust affect the yield to any appreciablt^ extent." At Rockport, Kans., 

 the same year, Bartholomew practically duplicated the Maryland 

 experiments under Galloway's direction. Bordeaux mixture seemed 

 to have a fairly good effect, and Bartholomew concluded that "whUe 

 no plat was entirely free from rust it is nevertheless a fact that the 

 ravages were reduced to a minimum on the 10-day plats sprayed 

 with Bordeaux mixture and ammoniacal solution of copper car- 

 bonate." In summmg up all of these experiments, Galloway con- 

 cluded "that the spraying treatments did, in some cases at least, 

 dimmish the amount of rust and similarly increased the yield of 

 straw and grain." Even with the most improved spraying methods 

 known at that time Galloway believed spraying would be imprac- 

 ticable on a large scale. That there was a possibihty of making it 

 practicable in the future was conceded. Hitchcock and Carleton 

 further carried on spraying experiments in Kansas in 1893 and 1894 

 (58, pp. 4-9). They used a large number of spra^-mg solutions. Some 

 of these, particularly potassium bichromate and ferric chlorid, were 

 somewhat effective in preventing rust, but the investigator found 

 it impossible to cover the fohage sufficiently to make them thoroughly 

 efficient. They concluded that "although the rust can be largely 

 decreased, we can not attain prevention as is done in such diseases 

 as the grape mildew. Furthermore, it is extremely doubtful if 

 spraymg of wheat or oats would pay, even if effective." 



Since these extensive spraying experiments very little work along 

 this line has been done in the United States, although more or less 

 desultory trials have been made. The trouble at all times in spraying 

 for rust has been the impossibihty of getting a spraying solution 

 that will cover all parts of the leaves evenly. The more or less waxy 

 bloom wliich occurs on the leaves of cereals causes the moisture to 

 drop off very easily, and it is almost impossible with any kind of 

 spraying apparatus to wet both surfaces of the leaves equally well. 

 The areas to be covered are so extensive that the expense of spraying 



216 



