1905.] DISEASES OF THE POTATO IN CONNECTICUT. 1 35 



As this trouble is carried on the seed tubers and as it be- 

 comes estabhshed in the soil, the preventive measures must be 

 the same as those used against scab. Two experimenters have 

 tried formalin and found this more or less efficient. The chief 

 objection to it is that sometimes the germination of the tubers 

 is retarded or injured enough to decrease the yield. 



4. Bacterial Blight and Rot. There is a bacterial disease, 

 usually to be found in our potato fields in June and July, that 

 attacks a plant here and there. This trouble generally infects 

 less than two per cent, of the vines. The plants assume a sickly 

 yellowish color, remain stunted, and finally wither and die. 

 These plants are easily pulled from the soil, when it is seen that 

 the stem below is more or less rotted. Even in the early stage, 

 while the plants are still green, if cross sections are made of 

 the stems the bundles will often show a brownish diseased 

 condition while the rest of the tissue is healthy. This diseased 

 condition of the bundles interferes seriously with the proper 

 conduction of water and plant food. The disease becomes most 

 prominent in the underground stem ; the tissues of the pith col- 

 lapse, leaving a hollowed center, in which stage the plants look 

 as if attacked by the stalk borer, and eventually the whole 

 stem rots off. Practically no potatoes are obtained from these 

 plants. 



Later in the season, especially after the true blight has killed 

 the vines, one often finds that the tubers are rotting from a 

 slimy, sticky, ill-smelling rot. This is also caused by bacteria 

 though sometimes attributed to the blight fungus. A year 

 ago this was a very common trouble in our potato fields. It 

 is quite possible that the bacterial blight of the stems and the 

 rot of the tubers are caused by the same organism. The fact 

 that the tubers usually begin to decay at the stem end points 

 to this relationship. 



In the way of preventive measures we have little to suggest 

 beyond care in the selection of seed and the removal of diseased 

 tubers from the field when dug. 



5. Fnsarium Wilt or Dry Rot is a fungous trouble in its 

 effects somewhat like the bacterial disease just described. The 

 fungus invades the stem underground and reaching the bundles 

 chokes these with a growth of its threads so that eventually 

 the water supply of the plant is cut off or greatly reduced, 

 when the parts above ground wither and die. We have had 



