356 agriculturp: op maine. 



OD 



POTATO WILT. 



There is a type of potato trouble common in some other 

 states, particularly in the west, but which as yet has not occurred 

 to much extent in Maine, which has been classed under the 

 name of wilt. Two different species of fungi have been found 

 associated with this, but this fact is unimportant from our stand- 

 point. The plants, as shown by the next picture, after they 

 reach the size when the tubers begin to set on, may wilt and die 

 more or less suddenly. Sometimes the lower leaves begin to die 

 before there is much evidence of wilt. If such plants are pulled 

 up and the stems cut across at or a little below the portion which 

 is at the surface of the ground you will find a grayish or brown- 

 ish discolored ring in the tissues near the outside. This is the 

 region of the water, conducting system of the plant, and the 

 wilting is due to the fungus growing up through and clogging 

 the vessels which supply the water to the tissues above. If the 

 tubers have begun to set and a cut is made just below where 

 the stem joins the tuber, a browning or discoloration may be 

 found here. Sometimes this ring of discolored tissue extends 

 some little distance from the stem end toward the tip. The 

 next picture shows some marked cases of the stem-end dis- 

 coloration. Next, a longitudinal section of the tuber affected 

 in the same way. The next, a dry rot of the potato caused by a 

 related fungus. 



The next picture shows a trouble, net-necrosis, which is by 

 no means uncommon in Maine, but while it greatly resembles 

 the appearance caused by the attacks of the wilt disease fungus 

 upon the tubers, has never been shown to be parasitic. However, 

 such tubers should not be planted, and the man who discards all 

 potatoes showing any suspicious discoloration in this way will 

 insure himself against the introduction of wilt. Once the fungus 

 gets entrance into the soil it may persist there for some time. 



SILVER SCURF. 



Silver scurf, shown in the next two illustrations, is probably 

 of minor importance as a potato disease. It is of particular 

 interest on account of the fact that it became very prevalent 

 and widespread in this country, especially in Maine, before it 

 v/as recognized even by the pathologists. It probably does very 



