THE RHIZOCTONIA DISEASE OF POTATOES. I97 



parts of Canada, producing injuries on the gi-owing stems similar to 

 those observed in Maine. He does state that in his experience the 

 fruiting stage of the fungus is not abundant but some good specimens 

 have been obtained from British Columbia and Alberta. 



An experiment where seed tubers bearing numerous sclerotia of the 

 fungus were soaked in corrosive sublimate and formaldehyde and then 

 planted at the Central Experimental Farm is described. Judging from 

 the numbers of sclerotia observed on the crop in the fall, corrosive 

 sublimate, used at one-half the strength usually employed, was decidedly 

 more efficient 'than formaldehyde. The crop obtained where the former 

 was used was practically clean while that produced where the formal- 

 dehyde treated seed tubers were planted was almost as badly covered 

 with sclerotia as the original lot of potatoes used for seed. 



Recently Gloyer (7) has made a comparative study of the efficiency 

 of formaldehyde solution, formaldehyde gas, and corrosive sublimate 

 for disinfecting seed tubers affected with Rhizoctonia. His conclusions 

 were that neither formaldehyde gas nor formaldehyde solution can be 

 depended upon to kill all of the Rhizootonia sclerotia but, "The stand- 

 ard corrosive sublimate treatment is thoroughly efficient. Even with 

 a I to 2,000 solution (half standard strength) all Rhizoctonia sclerotia 

 are killed." 



Rhizoctonia as a Cause of Potato Disease in Maine. 



As has already been pointed out, potatoes in Maine, in com- 

 mon with the rest of New England and apparently many other 

 parts of the United States, frequently show the so-called "black 

 scurf" or the sclerotia of the Rhizoctonia fungus upon their 

 surfaces. In fact the fungus is common and widespread in the 

 State and probably does not cause a great amount of damage 

 except to certain varieties of potatoes and in certain types of 

 soil. However, complaints have been received from time to 

 time, more especially from the southern and central portions of 

 the State, regarding poor and uneven stands of potatoes, unex- 

 pected low yields, sometimes associated with "early ripening" 

 or death of the tops from no apaprent cause but resembling an 

 abnormally early maturity. Undoubtedly these various troubles 

 result from a variety of causes, depending upon the conditions. 

 Some of these the writers have recognized for a number of 

 years, but the fact that Rhizoctonia is a factor, and often a very 

 important factor in the production of certain of the conditions 

 mentioned has been largely overlooked until recently. 



Ever since Highmoor Farm in Monmouth came under the 

 control of this Station several acres of potatoes have been 



