RUST OF ANTIRRHINUM. 59 



cyanide, acetic acid and sulfuric acid. Pammel (1893) attempted to 

 control rusts on oats and wheat by spraying with Bordeaux mixture, 

 but found no appreciable difference in the amount of the disease on the 

 sprayed and unsprayed plants. Stuart (1894) found that Bordeaux 

 mixture of standard and half strength solutions gave best results in the 

 control of carnation rust. Bailey and Lodeman (1895) sprayed carna- 

 tions with a mixture of Bordeaux mixture and soap. They also used a 

 mixture of copper chloride, lime and soap. They concluded that the 

 copper fungicides were most efficient in the control of carnation rust. 

 Stewart (1896) recommended spraying with weak copper sulfate for the 

 control of carnation rust. He found that the spores of U. Caryophjllinus 

 can germinate in a copper sulfate solution containing 0.0025 per cent 

 copper, and that there is slight germination in copper sulfate solutions 

 containing as much as 0.083 per cent copper. He found these spores 

 unable to germinate in 0.033 per cent solution of potassium sulfide. This 

 iuA-estigator found that if copper sulfate is applied to carnation cuttings 

 ill a solution strong enough to control the rust the plants are injured. 

 He found that Bordeaux mixture would not control carnation rust, and 

 recommended spraying carnations with a 0.56 per cent copper sulfate 

 solution, or with a 0.78 per cent solution of potassium sulfide. Sturgis 

 (1896) recommended potassium permanganate for the control of holly- 

 hock rust. Halstead (1897) sprayed hollyhocks with Bordeaux mixture, 

 and found rust on all the check plots, while but one sprayed plot showed 

 any rust. Kinney (1897) sprayed carnations Avith Bordeaux mixture, 

 and concluded that this treatment did not control the rust. Abbey (1898) 

 recommends Bordeaux mixture as an efficient fungicide in the control 

 of chrysanthemum rust. 



A survey of the literature on rust control by fungicides is not very 

 helpful. Some of the statements made are misleading and few are very 

 convincing; for instance, it is hard to see how potassium permanganate 

 could be of any great value in combating a rust. Potassium permanganate 

 destroys organisms by oxidizing them, and if in contact with oxidizable 

 material it very soon loses its power; hence it would be of no avail against 

 spores which subsequently fell upon the sprayed surface. Some investi- 

 gators found Bordeaux mixture efficient and some found it inefficient 

 as a fungicide for the control of rust. The narrow range of temperature 

 in which the spores can germinate may have been exceeded, and the 

 credit for no germination given to the fungicide instead of to a faulty 

 temperature which reduces or prevents germination. But the literature 

 does indicate that the rusts are very resistant to fungicides in general, 

 especially to copper fungicides. 



Sulfur Fungicides. 

 Dusting with sulfur has been used successfully as a control of P. Asparagi 

 Dec. (Smith, 1905 and 1906). Butler (1917) described a sulfur dust 

 control for rust of snapdragon. Stone (1917) recommended for the 



