MAINE AGRICULTURAL EXPERIMENT STATION. I913. 53 



leaves ot russeting the fruit and the increased efficiency in 

 scab control would more than pay the added cost, particularly 

 where the lime-sulphur concentrate is prepared at home. 



"little potato" OR RHIZOCTONIA DISEASE. 



Every New England housewife is familiar with the little 

 brownish or almost black patches or nodules of what is gen- 

 erally supposed to be dirt, very frequently found closely ad- 

 hering to the surface of potato tubers. Unless these are numei- 

 ous or large they are not usually noticed till an attempt is 

 made to wash the tubers. The notion that these bodies are 

 simply particles of closely adhering, black soil is farther 

 strengthened by the fact that they may be, with some difficulty, 

 removed by means of a stiff brush or the thumb nail, leaving 

 the skin of the potato smooth and uninjured. As a matter of 

 fact they are a mass of closely woven threads or the resting 

 stage of a fungus which has long been known under the name 

 of Rhizoctonia. It was classed among the so-called sterile 

 fungi till it was discovered that in the summer it grew up 

 around the base of growing potato stalks and there produced 

 spores of a definite type. 



Rhizoctonia is an almost universal inhabitant of potato soii3 

 all over New England and doubtless the same thing is true for 

 all potato growing sections of the country. While it has been 

 known for years as capable of attacking the below-ground parts 

 of the stems of a considerable variety of unrelated plants it 

 has not in the past been generally recognized or accepted as a 

 serious cause of potato disease, except in a very few localities. 



It appears to have been the cause of a partial failure of the 

 crop on one field in Maine for the past two years, and evidence 

 is being accumulated which shows that it does more or less 

 damage in some other sections, particularly on Irish Cobblers. 

 It may be that this fungus is one of the factors responsible 

 for imperfect germination some seasons. 



It is possible to give only a preliminary report on the occur- 

 rence of the disease in this state at the present time. Nothing 

 is known as to what conditions or kinds of soil are favorable or 

 unfavorable to it. The fungus is so common in all kinds of 

 soils that disinfection of the seed will be of little help unless 

 new land is being used for planting. If disinfection is at- 



