566 EXPERIMENT STATION RECORD. 



The downy mildew of melons {Plasmopara cuhensf's), while common 

 upon cucumber.s, has been previously reported but once as occurring 

 upon nmskmelons within the State. During August a number oi 

 specimens were sent to the author from vines which were badly 

 infested with the disease, every leaf on a 2-acre field being dead. 

 Investigation showed the fungus mentioned above. The same disease 

 is liable to attack cucumbers, and spraying experiments for its pre- 

 vention do not seem to have been conducted with uniform success. 

 The use of Bordeaux mixture as a partial preventive, or forcing the 

 melons and cucumbers by starting them earlier in the season and trans- 

 planting so that the fruits will be matured l^efore the usual time for 

 attacks of this mildew, are recommended. 



The disease of potatoes described was characterized b}^ the blacken- 

 ing and shriveling of the stalks which upon examination appeared to 

 be hollowed from an inch or so below the surface to 2 to 8 in. above. 

 The similarity in appearance between these Lollow stalks and the injury 

 caused ]jy potato-stalk borers led to a careful search, but no insects 

 were found. A microscopical examination showed neither fungus nor 

 bacteria. Upon the author's recommendation, all diseased vines and 

 those for a hill or two beyond the limit of the affected area were col- 

 lected and burned, and no further trouble was experienced by the 

 grower. 



A serious injury to peas is described, which is caused l)y the leaf- 

 spot fungus Ascochyta. There seems to be reason to believe that the 

 fungus attack is not primarily above ground but that it may be present 

 in the seed. Should the disease threaten serious injury in the futui'e, 

 it would be advisable to obtain seed from regions where it is not pres- 

 ent, and to select land which has not borne peas for a number of years. 

 In case it is necessary to use the same land for two or more successive 

 crops, as soon as the crop is harvested, all vestige of vines should be 

 gathered and burned. 



A ])rief note is gi\'en on leaf spot of alfalfa {Pseudopeziza medicag- 

 hiis). This disease has been fully described in the report of the Iowa 

 Station for 1897 (E. S. R., 10. p. 263). If the disease appears early in 

 the season, the alfalfa should be cut and fed immediately. If later in 

 the season, one practical means of combating it is by continuous crop- 

 ping, or watching for its appearanc(^, which would generally be at a 

 few points in the tield, and cutting and burning the affected plants. 



The disease of peppers described is that of anthracnose {Colletoti'l- 

 chuvi nigrum). This is reported to have occurred during the past sum- 

 mer in fields in which at least 25 per cent of the fruit was rendered 

 worthless b}- the fungus. No experiments have been attempted for 

 its prevention, but based on experiments conducted elsewhere it is 

 thought that irrigation and mulching would prove advantageous. 



