DISEASE AND ITS PREVENTION 81 



disease causes the vine to wilt, and often leaves the tubers 

 about half the size they should be, and these diseased tubers 

 decay quickly. 



When the plants are infected with wilt or blight, there 

 is always a shortage of starch, causing them to decay quick- 

 ly. If this does not happen, the food value will be greatly 

 decreased. When the tuber is first formed it consists chief- 

 ly of water, and as it grows the starch is formed. Changing 

 the seed from one soil to another from year to year not only 

 increases the yield, by making the seed more free of disease, 

 but by increasing the starch content. As the feed roots give 

 nourishment to the vine, when the vine is affected by these 

 diseases, the food supply is cut off from the tuber, and, in- 

 stead of plant food, the disease in the stem is taken into the 

 tuber. 



The hills of potatoes with wilt always have small tubers, 

 and, if these small tubers of a field are not eliminated, they 

 will be used as seed, and, consequently, the wilt will appear 

 the following season. The wilt is always introduced into a 

 clean field by a diseased tuber. The only way known to con- 

 trol this disease is to eliminate the diseased tubers from 

 the stock. 



The tuber moth is a small moth or fly and generally ap- 

 pears in the tubers that are dug and left in a pile. They are 

 seldom seen in the peat land, but do appear at times. They 

 can gain a better foothold on the drier, cloddy soils. In early 

 plantings, I always dig and market before the potatoes are 

 mature, before the tuber moth appears. They seldom bother 

 a fall crop, planted in July or August, unless the soil is clod- 

 dy, which, of course, is an unfavorable condition for the soil 

 to be in for potatoes. The potatoes that are dug before fully 

 matured are less liable to disease, as they have less time to 

 grow, and the disease does not have the time to go into the 



