IV. EXPERIMENTS AND OBSERVATIONS ON 

 SOME DISEASES OF PLANTS.* 



F. C. STEWART. 



SUMMARY. 



I. The popular opinion that green manuring with rye will pre- 

 vent potato scab has been found, by experiment, to be without 

 foundation in fact. Of the six plats employed in the experiment 

 three were green manured with rye, while the remaining three 

 (alternating with the rye plats) were used as checks. On all six 

 plats the tubers were badly scabbed, the rye plats being even 

 worse than the check plats. 



II. An attempt to communicate the potato stem-blight by 

 means of diseased " seed " failed. Unsuccessful attempts were 

 made, alsio, to inoculate tomatoes, peppers, egg-plants, petunias 

 and Chinese lantern plants by placing pieces of diseased tubers 

 about their roots. The conclusion is that the disease is purely 

 physiological and that there is. no danger of spreading it by plant- 

 ing diseased tubers. 



III. It has been shown by experiment that common salt solu- 

 tion applied to the foliage of carnations or to the soil in which 

 they are grown will neither prevent rust nor give the plants a 

 more vigorous growth. 



IV. On Long Island it is unnecessary to commence spraying 

 cucumbers (no matter what the date of planting) until the middle 

 of July. In an experiment at Floral Park spraying increased 

 the yield of early cucumbers at the rate of 30,450 fruits per acre. 



Downy mildew is easier to control by spraying than is anthrac- 

 nose. 



♦Reprint of Bulletin No. 1S8. 



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