138 BOARD OF AGRICULTURE. [Jan., 



Second, the full or partial yield of the plants may be obtained 

 and then cut down more or less by the subsequent rotting of the 

 tubers. If I can judge accurately from an experience extend- 

 ing over only three seasons, the blight, when it comes on early 

 and suddenly, as it did in 1902, may cause a small crop with but 

 few rotten tubers ; but when it develops late and lags along 

 slowly to the end of the season, as it did somewhat in 1903, 

 but more especially this past season, we may grow a larger 

 crop that suffers severely from rot. This rotting no doubt 

 develops worse in a season like the past because more spores 

 through a longer period are washed down onto the tubers than 

 are when the vines are blighted and dead inside of a week. 



Finally let me give briefly the preventive measures that may 

 be used against this fungus. We may grow the early varieties 

 with their smaller yield and higher prices. These are often 

 nearly matured by the time the blight appears and so suffer 

 much less than late varieties. However, they are not without 

 their diseases, and on the whole are not so popular with growers 

 as are the late varieties. Knowing that the blight is carried in 

 the tubers, all potatoes showing any signs of the disease, 

 especially a reddish discoloration of the tissues when cut open, 

 should be rejected. While evidence so far goes to show that it 

 makes no differejice if rotten tubers are left in the field, yet we 

 may be mistaken about the ability of the fungus to develop 

 winter spores in these, in which case it would be an error not to 

 gather them up. Cultivation that tends to cover the tubers 

 deeply in the soil and at the same time keep the ground from 

 becoming wet — such as ridge culture — seems to be best 

 adapted to prevent the tubers from rotting. This system also 

 tends to hold up the vines and allow freer circulation of the air 

 for drying out the soil and evaporating moisture from the 

 leaves. Too close planting and too luxuriant growth of foliage, 

 for the opposite reason, favor a more rapid development of the 

 blight. Some work has been done on the selection and breed- 

 ing of blight-proof varieties. The government is said to be 

 at work along this line. One rarely sees any indication of 

 blight-proof individuals in our fields, so we should not be dis- 

 appointed if we get no relief from this direction. Spraying 

 with bordeaux mixture has given more or less excellent 

 results. The writer's experiments along this line have given 

 some encouraging and some discouraging figures as to yields. 



